What are errors of/in radar?
What are errors of/in Radar ? Heading marker alignment. EBL not alignment. Gyro input with error. Improper tuning. Improper range. Blind sector. Adjustment rain clutter/sec clutter. Own vessel date input error. Range & bearing discrimination. Beam with distortion. Side lobe echo. Multiple echo. Second trace echo.
What is heading marker misalignment?
Heading misalignment: Heading markers are usually manually set on the radar on a vessel. This means that the markers may end up being misaligned for one reason or the other. To ensure the heading marker is not misaligned, you will need to point two vessels directly at each other.
What is beamwidth error in radar?
Beamwidth error: When the radar beam from the vessels moves away from the vessel, the width of the beam tends to widen. This causes distortion of the objects being detected. This distortion error increases as the vessel moves further away from the vessel.
What are the factors that affect the echo strength of radar?
This usually leads to a significant reduction in the strength of the echo. Attenuation is more pronounced in instances where there are a high frequency and short wavelengths. 4. Double echoes: These happen when the radar signals bounce off some parts of the ship and back into the receiver. 5.
What is a heading marker error radar?
When the heading marker on the screen does not exactly line up with the ships heading. When the echo from a target dead ahead does not lie exactly on the heading line we have a heading marker error. These may have serious effects on the radar picture and have been the cause of many collisions.
What are the radar errors?
Radar Errors: Indirect Echo (reflected): Range true but bearing of a vessel in direction of the obstruction. (mast, funnel or containers on a container ship) Multiple Echo: Bounce of energy back and forth, entering antenna in each bounce. . . .
What is head-up mode in radar?
A vessel’s radar display provides a choice of orientation modes. The natural mode is the one already described where the heading direction of the ship, and therefore the heading line, is vertically upwards on the display. This is known as the head-up mode.
What causes the shadow and blind sectors?
Shadow Sector: A sector on the radarscope in which the appearance of radar echoes is improbable because of an obstruction near the antenna. While both blind and shadow sectors have the same basic cause, blind sectors generally occur at the larger angles subtended by the obstruction.
What are the causes of radar faulty interpretation?
Interpretation of information on a radarscope Among the factors producing errors in interpretation are: bearing resolution, range resolution, radar shadows, multiple echoes and false echoes. — Bearing resolution is the minimum difference in bearing between two targets at same range which can be seen clearly.
What is accuracy in radar?
Radars Accuracy. Accuracy is the degree of conformance between the estimated or measured position and/or the velocity of a platform at a given time and its true position or velocity.
What is the difference between heading and course over ground?
Course Over Ground (COG) is the actual direction of motion (the intended direction of travel). While heading is the direction in which a vehicle/vessel is pointing at any given moment (https://www.applanix.com/news/blog-course-heading-bearing/).
What is the difference between head up and course up?
1:373:50Understanding North Up, Course Up & Head Up on your Garmin GPS …YouTubeStart of suggested clipEnd of suggested clipThe right is east the bottom is south and the left is west. When the gps is in north up what thatMoreThe right is east the bottom is south and the left is west. When the gps is in north up what that means is that your screen will not move the boat will move throughout the screen if the boat is facing
What are the steps to setting up a radar?
Proper setting of radar displayTransmit the radar in maximum range.Set STC (sea clutter) to minimum.Set FTC (rain clutter) to minimum.Set the gain control to maximum (the screen should show mostly radar noise)Now adjust the gain control to show a very small amount of noise (only a few noise spots on the screen)More items…
What causes false echo on radar?
Indirect or false echoes are caused by reflection of the main lobe of the radar beam off ship’s structures such as stacks and kingposts. When such reflection does occur, the echo will return from a legitimate radar contact to the antenna by the same indirect path.
What are the 3 different types of false echoes?
Many types of false radar echoes are observed on a ship-mounted radar scope, including side lobe echoes, interference echoes, second trace echoes, and others.
What are radar false echoes?
False echoes are known as anomalous propagation (AP). It is an echo that is not precipitation. Radar return from AP is unpredictable, often contaminates precipitation measurements and can cause the generation of erroneous rainfall estimates used in hydrology products.
What does it mean when a heading marker is misaligned?
This means that the markers may end up being misaligned for one reason or the other. To ensure the heading marker is not misaligned, you will need to point two vessels directly at each other.
What are the input limitations of radar?
Input limitations: There are a number of sources that are used to feed information into modern radars. Some of these sources include GPS and compasses. These inputs may also have their own limitations that may have an effect on the radar itself.
Why is radar important?
It is used to detect other ships at sea and any other land obstacles. It is one of the most important safety components at sea and near the shores. But like all radar systems, marine radar has its own limitations and errors. Below are some of the errors and limitations.
Why does radar report a curved coastline?
This is because of the distance the radar takes to reach and return to the receiver from areas that are further away from the centerline of the vessel. 4. Input limitations: There are a number of sources …
Why are radar signals affected by clutter?
1. Clutter: Radar signals are affected by clutter especially from the sea and those caused by rainfall. This is why clutter controls are provided. However, the clutter controls need to be used with great caution because they may end up suppressing weaker objects that are navigating within the clutter zone.
What is index error?
1. Index error: This is the difference between the actual range between two points on a map and the range detected by the radar. This error can be observed when the vessels seat abeam between two points.
What is indirect wave error?
Indirect wave error: When a radar beam is emitted from the vessel, it is supposed to travel in a straight line directly to the contact. However, there are instances where the beam falls into the sea and it is deflected further which makes it travel a longer distance than if it would have traveled in a straight line.
Part 1: Things to Know about the SOS Marker Error
Before I discuss different ways to fix an SOS marker error with JPG images, let’s cover some basics. Ideally, just like any other data file, JPG pictures also have a dedicated header that contains all kinds of crucial details about them.
Part 2: How to Fix an SOS Marker Error for your Images?
It has been observed that Adobe Photoshop users mostly encounter an SOS marker error with JPG files while exporting a project. Though, the SOS marker problem can take place due to any other reason and can be resolved in the following way:
Closing Words
As you can see, there can be so many reasons for causing the SOS marker error with JPG files. Though, to fix an SOS marker error, you can try to open your images with a compatible application or avoid any forceful conversion of the file.
FAQs
How do I fix the “SOF DQT or DHT JPEG marker is missing before a JPG SOS marker” error on Mac?
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After the heading marker has been checked for alignment, the display should be observed for a short period to ensure that the heading marker is following variations in the ship’s heading.
From: Radar and ARPA Manual (Third Edition), 2014
Basic Radar Principles
Alan Bole, … Andy Norris, in Radar and ARPA Manual (Third Edition), 2014
1.4 Display Modes
There are a number of display modes on a modern radar for determining exactly how the radar shows information in relation to the outside world. These cover three different areas, which are referred to as orientation, motion and stabilization modes. The orientation mode defines how the ‘vertical’ direction of the display aligns with the outside world horizontal (azimuthal) direction; the motion mode defines how the own-vessel moves with respect to the display; and the stabilization mode defines how absolute movement is referenced – relative to the ground or relative to the sea. Taking the display to be a conventional graphical representation in x and y coordinates, it is the y-direction that is considered to be vertical and the x-direction as being horizontal.
1.4.1 Orientation Modes
A vessel’s radar display provides a choice of orientation modes. The natural mode is the one already described where the heading direction of the ship, and therefore the heading line, is vertically upwards on the display. This is known as the head-up mode.
There are two other orientation modes available. One is termed north-up, where the vertical direction represents true-north and the other is course-up, where the vertical direction of the display represents the desired course of the vessel.
1.4.1.1 Head-Up Orientation
This orientation, where the heading marker is always vertical on the display, is illustrated in Figure 1.13. As the vessel’s heading changes, so does the orientation of the displayed image – the image is vessel stabilized, aligning with the view from the bridge windows, but is unstabilized with respect to true-north. The figure shows the situation just before and after a course change. This was the only orientation mode available on very early marine radars because of cost and technological limitations. However, the only significant attraction of using the basic head-up mode today is that it does not need a working gyro or compass input to the radar, unlike the other orientation modes on a modern radar, north-up and course-up. These modes, described separately in the sections below, stabilize the orientation of the radar image. For this reason, head-up mode is often described as unstabilized. If compass problems are encountered its use may be essential and so needs to be fully understood.
Figure 1.13. Head-up orientation (unstabilized).
The head-up unstabilized mode is superficially attractive because of the very fact that the displayed radar image corresponds directly with the scene as viewed through the wheelhouse window. A well placed display unit, close to the bridge windows and facing forwards, means that irrespective of whether the user is viewing the radar screen or looking forward through the wheelhouse window, objects on the starboard side of the ship will lie on the right of the display and those on the port side will lie on the left.
However, this orientation mode became generally little used after north-up stabilization was introduced on marine radars. This was for a number of reasons. Firstly, the head-up image of earlier radars could become very unclear when in head-up mode. The ‘afterglow’ trail of static targets, especially of extended targets such as land masses, could obliterate critical small moving targets when the image rotated. This is not such a serious problem on modern radars set to head-up mode because of the digital processing technology now employed. Secondly, small yawing movements of the vessel create corresponding oscillations in the orientation of the radar image, which can make precise target range and bearing measurements difficult. This generally remains an issue, even on a modern radar set to unstabilized head-up mode. The third issue is that the bearing scale on an unstabilized head-up radar is not true-north related, and therefore creates extra work in establishing the true bearing of targets.
A particular reason for north-up mode becoming so frequently used was the general attractiveness of using an orientation which matches that of the paper chart, since it considerably benefits situation awareness. In fact, with the advent of electronic charts, which can also be displayed in head-up mode, the use of a head-up orientation mode potentially becomes more attractive. Before the era of electronic charts the use of head-up mode was mainly confined to special situations, such as when negotiating rivers, estuaries, narrow channels and locks, or when no compass interface was available. While course-up mode, described in Section 1.4.1.3, is a good alternative, many radars have an advanced head-up mode that is generally called stabilized head-up. This uses the gyro/compass input to orientate the bearing scale such that the heading direction is referenced relative to true-north, together with any other indications of bearing on the radar display. Smart processing can also prevent small yawing motions of the vessel creating an oscillating image, generally allowing targets, measurements to be easily performed, and also improving the clarity of the display.
It should be borne in mind that in both stabilized and unstabilized head-up mode, an unwary or poorly trained observer can be misled by the angular rotation of the display as the own-vessel heading changes. For example, a small change of course by the observing vessel may give the impression that the bearing of a target is changing, while in fact the true bearing is remaining constant. The extremely important topic of systematic observation of target movement is discussed at length in Chapter 7.
1.4.1.2 North-Up Orientation
In north-up orientation, the heading marker is aligned with the graduation on the bearing scale that corresponds with the instantaneous value of the ship’s heading relative to true-north. It means that 000° on the bearing scale aligns with true-north. Thus the observer views the picture with north at the ‘top’ of the screen and it is for this reason that the orientation is so named. Figure 1.12(b) shows the same situation as that displayed in the head-up mode in Figure 1.12(a) but with the system set to north-up, assuming that the own ship is on a heading of 280°. Compass stabilization is essential to maintain north-up orientation, not least when the observing vessel alters course or yaws about its chosen course (Figure 1.14, which compares the cases for head-up, north-up and course-up operation). The stabilization signal can be derived from any transmitting compass, but in practice the signal source is often a gyro compass, which is compulsory for larger vessels. The principles of north-up orientation are illustrated in Figure 1.15.
Figure 1.14. Target trails and the effect of yaw.
Figure 1.15. North-up orientation (stabilized).
A major benefit is that the orientation compares directly with that of the paper chart. Also, because the display is stabilized it removed the significant disadvantage of earlier radars that changes in heading caused significant blurring of the radar displayed image when in head-up mode. These two factors have led to north-up mode becoming the most commonly used orientation option on most vessels. It also remains relevant when using electronic charts in north-up mode. Some users find using electronic charts and radar in north-up preferable, as it aligns both the radar and the chart image with the mind image they have of the area, easing situation awareness. For others, especially when on a southerly course, they find north-up awkward or uncomfortable to view as it appears ‘upside down’.
1.4.1.3 Course-Up Orientation
In course-up orientation the vertical direction on the display is aligned to the bearing which represents the desired course of the vessel. This can be obtained either automatically or semi-automatically from route planning information stored within the radar or by the operator selecting a particular course. By virtue of the compass stabilization, changes in the vessel’s instantaneous heading are reflected by sympathetic angular movements of the heading marker, thus maintaining the ship’s course (the reference course) in alignment with the display’s vertical direction. For the same reason, the angular wander of echoes associated with an unstabilized display is eliminated. On modern radars the bearing scale will be relative to true-north, but older radars may have the vertical direction always shown as 000°, representing the desired course. Figure 1.16 illustrates course-up orientation.
Figure 1.16. Course-up orientation (stabilized) – resetting the reference course.
Provided that the observing vessel does not stray very far from her chosen course, this orientation can be more effective than a stabilized head-up orientation because it eliminates all angular wander of the picture due to yaw, while maintaining the heading marker approximately vertical on the display. Inevitably a major alteration of course will become necessary either due to the requirements of collision avoidance or to those of general navigation. When the vessel is steadied on the new course the orientation, although not meaningless, will have lost its property of being substantially head-up. The problem is that the orientation is still previous-course-up and the picture should be re-oriented to align the heading marker to the vertical direction of the display (see Figure 1.16(d)).
1.4.1.4 Choice of Orientation
The fundamental function of any civil marine radar is to provide a means of measuring the ranges and bearings of targets for collision avoidance and the determination of the observing vessel’s position in order to ensure safe navigation. The ease with which these objectives can be achieved is affected by the choice of orientation. Where the various techniques of collision avoidance and navigation are described in this text, appropriate attention will be given to the influence of orientation. The practical use and setting up of orientations is discussed in Chapter 6. Table 1.1 summarizes the essential features of the three described orientations.
Table 1.1. Picture Orientations Compared
| Feature | Orientation | ||
|---|---|---|---|
| Head-Up, Unstabilized | North-Up, Stabilized | Course-Up, Stabilized | |
| Blurring when observing vessel yaws or alters course | Yes: can produce very serious masking | None | None |
| Measurement of bearings | Awkward and slow | Straightforward | Straightforward |
| Angular disruption of target trails when observing vessel yaws or alters course | Yes: can be dangerously misleading | None | None |
| Correspondence with wheelhouse window view | Perfect | Not obvious | Virtually perfect except after large course change |
| Correspondence with chart | Not obvious | Perfect | Not obvious |
Except in emergency situations, when azimuth stabilization has been compromised by equipment failure, head-up unstabilized orientation has nothing to offer other than its subjective appeal, because by its very nature it regularly disrupts the steady-state condition conducive to measurement of bearing and tracking of echo movement (see Figure 1.14(a)). The stabilized north-up and course-up orientations do not exhibit this angular disruption and hence are equally superior in fulfilling the fundamental requirements. Fortunately they are complementary in that while one is north-up, the other is orientated in such a way as not to alienate the user who has a ship’s-head-up preference. On some radar systems, stabilized head-up orientation may be included as an alternative to the use of course-up mode.
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Automatic Radar Target Tracking, Specified Facilities
Alan Bole, … Andy Norris, in Radar and ARPA Manual (Third Edition), 2014
4.12.3.2 The ‘Passing Clear’ Case
In the non-collision case where the heading marker does not violate one of the danger areas, the areas themselves will move across the screen, changing in shape and position. The movement will be very similar to that described for the collision point in Figure 4.22, depending on whether the observing ship is heading farther ahead than the cross-ahead position or farther astern than the cross-astern position. In the case of the dual areas of danger, although the movement will generally be the same as that shown for the dual collision points, a special case can arise when two danger areas may merge. This special case indicates the possibility of two cross-astern positions existing but no cross-ahead position. It is also possible that cross-astern positions may exist and an area of danger be drawn, which does not embrace an actual collision point.
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Operational Controls
Alan Bole, … Andy Norris, in Radar and ARPA Manual (Third Edition), 2014
6.2.5 Setting the Orientation of the Picture
The picture must be correctly orientated so that the heading marker intersects the correct graduation on the circular bearing scale surrounding the radar picture. In many older systems it was necessary to rotate the picture manually, whereas in modern systems it is an automatic alignment as the azimuth scale is part of the graphics. Nevertheless the display should be observed to ensure that the heading marker has aligned correctly according to the numerical value of the compass course in use, as well as to check that the numerical value indicated on the radar data display is the same as that indicated on the actual compass.
After the heading marker has been checked for alignment, the display should be observed for a short period to ensure that the heading marker is following variations in the ship’s heading. The observer must decide between three options, head-up (unstabilized), north-up (stabilized) and course-up (stabilized) as discussed in Section 1.4.1. Modern sets are usually provided with a three button toggle control. The two stabilized options are to be much preferred if the intention is to do manual paper plotting or taking bearings for navigation. They are essential if using an ARPA as stabilized options require the input from a working compass.
The digital read-out of the compass should be clearly displayed on the screen along with the source (e.g. ‘gyro compass 2’). There will be a method (usually in the menu system) of changing to different compass sources when available. Older compass repeater systems merely reproduced the changes in headings of the vessel and it was also essential to check that the compass heading on the radar was aligned with the master compass, and to periodically check that this was still the case.
In the particular case of course-up orientation, it will be necessary to reset the reference course each time the vessel makes a sustained alteration of course. In modern systems it is merely necessary to press some form of reset control when the vessel is steady on the new course.
The alignment of the heading marker on the bearing scale should not be confused with that of the alignment of the heading marker with the ship’s fore-and-aft line. The latter operation is concerned with ensuring that the heading marker contacts (see Section 2.5.3) close and produce the heading marker signal at the instant the radar beam crosses the ship’s fore-and-aft line in the forward direction. This alignment cannot be checked without reference to both visual and radar observations (see Section 6.6.8).
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ARPA – Accuracy and Errors
Alan Bole, … Andy Norris, in Radar and ARPA Manual (Third Edition), 2014
9.5.4 The Effect on the PPC of Incorrect Data Input
9.5.4.1 Errors in Speed Input
If incorrect speed is input to a collision situation, the collision point (see Section 4.11) will still appear correctly on the heading marker, but at an incorrect range, and will move down the heading marker at an incorrect speed.
In the case where there is, in fact, a miss distance, the collision point will appear in the wrong position, which may give rise to a misjudgement of the danger or urgency of the situation. Figure 9.8 shows how the collision point may be displaced due to a speed error in the two cases where the target is crossing ahead and crossing astern.
Figure 9.8. The effect on the PPC of a speed error.
A, target passing astern, correct speed used.
B, target passing ahead, correct speed used.
A1, B1, PPC appears here if a speed greater than the correct value is used.
A2, B2, PPC appears here if a speed less than the correct value is used.
9.5.4.2 Errors in Course Input
The behaviour of the collision point when an error in the course is input is too complex to allow definition of a pattern. If the error occurs only in the calculation and does not appear in the position of the heading marker, the collision point could appear on the heading marker in a miss situation. More dangerously, a collision point could appear off the heading marker in a collision situation. When the same error appears in both heading marker and calculation, as might occur due to a gyro compass error, the collision case will always show the collision point on the heading marker.
Similarly, if a miss distance exists, the collision point will not be on the heading marker.
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Radar Plotting Including Collision Avoidance
Alan Bole, … Andy Norris, in Radar and ARPA Manual (Third Edition), 2014
7.10.3 The Reflection Plotter
The work involved in the transferring of data from the radar display to a plotting sheet is both time-consuming and a potential source of errors and so is a discouragement to practical plotting. For those having to plot manually, the advantage of being able to plot directly on the screen surface was recognized at a very early stage in the development of radar. As a result, the anti-parallax reflection plotter was developed.
It has rapidly disappeared from general use due to the introduction of the raster-scan display. The UK regulations (see Section 11.4.1) still require that plotting facilities shall be at least as effective as a reflection plotter.
7.10.3.1 The Construction of the Reflection Plotter
As can be seen from Figure 7.30, the plotting surface has the same curvature as the CRT. By inverting it and placing a flat partial reflecting surface midway between the two curved surfaces, it is possible to put a mark on the concave plotting surface such that its reflection will be aligned with the target’s response on the CRT surface, irrespective of where the observer’s eye is positioned. This overcomes the problems of parallax which would arise if one were to try to plot on the plastic cursor placed some inches above the CRT surface.
Figure 7.30. The reflection plotter.
7.10.3.2 The Practical Use of Reflection Plotters, Including the Use of the Perspex Cursor and Parallel Index
Plotting is carried out on the plotting surface as if working on a plotting sheet, but it is the ‘reflections’ which must be continually observed. Two techniques are peculiar to reflection plotting (Figure 7.30):
- a.
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It was necessary to make a ‘scale’ rule for measuring distance on the plotting surface. This was done by brightening the range rings, placing a mark on each ring and then, using stiff card, marking the position of each ring on the card. Sub-divisions may be put in by eye or more precisely, using the variable range marker. See Figure 7.31.
Figure 7.31. Constructing and using a scale rule.
- b.
-
It was necessary to draw parallel lines on the plotter surface, for example OW parallel to the heading marker. This was done by lining up the Perspex cursor with the heading marker. The parallel index lines on the cursor were then parallel with the heading marker. The edge of the scale rule was then aligned with the nearest parallel index line below it – this may mean that one had to move the position of one’s head slightly, or slide the card a short distance.
Note: When drawing a line from a point, tangential to a range ring, for example when determining the time to resume, it was best first to mark the position of the range ring on the plotter surface.
7.10.3.3 Changing Range Scale
The reflection plotter had two distinct advantages: namely, it eliminated the need for reading and transferring of ranges and bearings to a plotting sheet and it maintained the immediate contact between display and plot. However, there was often a certain reluctance on the part of the observer to change range scale because of the perceived potential loss of the plot. Nonetheless, it is important that when targets are close, the most appropriate range scale was used. This meant adapting the plot to the new range scale. As can be seen in Figure 7.32, once the target is within the inner portion of the screen, the range scale was changed and the predicted apparent-track line A2A3 drawn parallel through the new position of the target.
Figure 7.32. Changing range scale on a reflection plotter.
It can often prove useful to retain the original plot and, provided that the lines do not become confusing, they can be left on. If available, different colour wax pencils could be used for each range scale to aid clarity.
7.10.3.4 The Use of the ‘Free’ EBL to Draw Parallel Lines (See Section 6.6.5)
The ‘free’ EBL was often extremely useful for transferring parallel lines in conjunction with a reflection plotter in preference to the use of the parallel lines on the Perspex cursor.
The EBL origin is positioned on the reflection of the line to be transferred and is rotated so that it is aligned with the line to be transferred. The EBL maintained its orientation as it was moved about the screen using the joystick (Figure 7.33).
Figure 7.33. The use of the ‘free’ EBL to draw parallel lines.
Note: Transfer the line to the plotting surface if the EBL is required for another use; if not, leave it in place.
7.10.3.5 Fixed and Rotatable Surfaces – Use with a Ship’s Head-Up Unstabilized Display
While using a reflection plotter on a ship’s head-up unstabilized display, if it became necessary to alter the own ship’s course, the target and plot became out of alignment as the own ship changes course. For example, in Figure 7.34, after an initial plot, the own ship alters course 55° to starboard; at the completion of the manoeuvre, the plot and target will be as depicted. To realign the plot to the target, it was necessary to rotate the plotter surface anticlockwise (i.e. in the opposite direction to the alteration of course) by the amount which the own ship has altered course.
Figure 7.34. The use of a rotatable plotting surface. (a) Before or during alteration of course. (b) After rotation of the plotting surface.
When a rotatable surface has not been provided, there are means by which the plot can be continued. However, they can be complicated and consequently confusing, and are best avoided. When a fixed-surface plotter was provided, it was virtually essential that the true-north-up stabilized presentation was selected (see Section 1.4.1.2).
7.10.3.6 Flat and Concave Surfaces
The concave surface can be rather awkward to work on and so more complex plotters were provided with flat plotting surfaces. This was made possible by using a curved partial reflecting surface. However, apart from that, its use was exactly the same as for a plotter with a concave plotting surface.
7.10.3.7 Use in Conjunction with Parallel Indexing
The provision of a reflection plotter made it possible for a prepared navigation plan to be marked out on the plotter and the movement of particular navigation marks observed in relation to their predicted movement. Any deviation from the pre-planned track will be readily apparent and compensation can be made (see Section 8.4).
7.10.3.8 Reflection Plotters and Raster-Scan Displays
No manufacturer has produced an optical reflection plotter which can be used with a television-type rectangular CRT or liquid crystal display (LCD). There is an inherent assumption that in the unlikely event that the ARPA is not working but the radar is, then any manual plotting will have to be done on paper.
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Navigation Techniques Using Radar and ARPA
Alan Bole, … Andy Norris, in Radar and ARPA Manual (Third Edition), 2014
8.4.2 Preparations and Precautions
8.4.2.1 Pre-Planning
Navigators who conduct their vessels in confined waters using blind pilotage techniques such as parallel indexing must never lose sight of the fact that safety margins are often minimal and on no account must operator errors be allowed to creep in to the parallel-indexing data. By the time an error becomes apparent it can very likely be too late to recover the situation. Considerable care must be taken therefore in deriving the parallel-indexing data from the navigation chart and transferring it onto the radar display, to ensure that it is as accurate as possible. All data should be cross-checked and, indeed, the whole process of acquiring the parallel-indexing data is best carried out when there is a minimum of pressure and distraction. It would be inviting trouble to attempt to derive and use parallel-indexing data in quantity when the vessel is already proceeding through the confined area. Most ‘off the cuff’ work suffers from inadequate checking and hence is susceptible to error. On occasions, parallel indexing may be employed directly from the radar screen without any pre-planning (see Section 8.4.7), but generally the need for parallel indexing should be assessed during the passage-planning stage and all the necessary data to carry out the task, extracted from the chart and stored in suitable form (see Section 8.4.3.5), hours before it is intended to make use of the data. Only by doing this can one be sure of reliable data of sufficient quality to realize the full benefits of parallel indexing.
8.4.2.2 Preparing the On-Board Equipment
The radar set is an integral part of the parallel-indexing process and must be in proper working order, able to display the indexing target, be operated correctly, orientated and stabilized and with proper discrimination and accuracy. Particular care must be exercised with the tuning, gyro compass error and heading marker accuracy (see practical setting-up procedures in Chapter 6). The electronic index lines will be used, so the readout accuracy must be confirmed. Similarly, if the bearing lines and variable range markers are also to be used, then any errors must be removed or known so that due allowance can be made.
8.4.2.3 The Radar Presentation
In theory, parallel indexing can be employed either on a relative-motion north-up azimuth-stabilized display or on a ground-stabilized true-motion display.
There are practical difficulties in achieving a reliable ground-stabilized display with a simple radar without ARPA or a GNSS position input (see also Sections 6.2.6.2 and 8.4.5). For instance:
- 1.
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Obtaining the present tidal rate and set can be time-consuming and not necessarily very accurate. Even if good values are obtained, changing conditions may mean that the values need to be frequently reassessed.
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An accurate knowledge of our own ship’s course and speed through the water is not always easily available, especially when using unreliable speed logs.
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Given good information regarding the vessel’s movement over the ground, it still remains for the radar equipment to track accurately in response to this information. This cannot always be taken for granted.
Bearing in mind that parallel indexing is intended to improve navigational safety, the operational difficulties mentioned above that could influence the reliability of this work means that true-motion parallel indexing must be considered second best to relative-motion parallel indexing for a simple radar with azimuth stabilization.
8.4.2.4 Selecting the Indexing Target and its Effect on Accuracy
The indexing target is a chosen radar target which appears on the PPI and whose movements relative to the observing vessel as it transits a particular confined area will be closely monitored. If everything goes according to plan, the ship will be manoeuvred to make this target track along the lines that have been drawn on the reflection plotter, or at least within certain limits from these index lines, and in so doing the navigator can ensure that the vessel follows the chosen track line.
For a target to be suitable, there are certain conditions which must apply to the indexing target:
- 1.
-
It must be a good radar target, that is clearly visible on the PPI at the ranges at which it is intended to be used.
- 2.
-
It must be identifiable among all the other land targets in the area and also there must be some recognizable feature on the target to which all the measurements can be related. This latter requirement can be difficult to resolve in the case of non-point targets, since most change their radar aspect and therefore their appearance as the relative position of the ship changes (see Section 8.2).
The navigator, in preparing for parallel indexing, must study the chart of the area with particular care to find the most suitable indexing targets, such as the end of a breakwater, the tip of a headland, small islands, isolated rocks, isolated lighthouses, etc. Lighted navigation marks are of no consequence in this context of course and it is usually advisable to not rely on a floating navigation mark as an indexing target (except as provided in Section 8.4.6.1), not so much because of their slight variations in position but because of the possibility of their not being there at all when the vessel arrives. It is impossible to change all the pre-worked parallel-indexing data to another target at short notice.
Note: Whenever a vessel is operating in a confined area where parallel indexing can be useful, the navigator is advised to watch the radar picture carefully with a view to identifying suitable indexing targets for use on a future occasion. This method is far more certain than studying the chart. This information should be stored for future use, for example by marking the chart.
Another important consideration is the choice of the working range scale for the radar. Inevitably, the longer the range scale, the lower the accuracy with which one can monitor the position. The navigational requirements will determine the accuracy required and also the safety margins which will apply. The navigator must therefore be sure that the working range scale of the radar meets this accuracy requirement and that the selected indexing target will be ‘in range’. This should not be taken to imply that a complete parallel index transit should be completed on one range scale. As accuracy requirements change, so should the working range scale. Hand-drawn index lines need to be redrawn at different range scales. It is a great benefit that modern electronic index lines change their position automatically with changes in radar range scale. Similarly, as the vessel progresses through the confined area, so the indexing target will also need to be changed.
8.4.2.5 Preparing the Navigation Data
Parallel indexing is part of the navigation of the ship and therefore any guidance lines that appear on the display should be directly related to actual data of navigational significance on the chart, for example the safety margins and course lines (Figure 8.4).
Figure 8.4. Adjacent dangers, margin lines and course lines.
In planning a passage through a confined area, the adjacent dangers need to be assessed in detail. Adjacent dangers in addition to shoal water can include areas of strong tidal sets and the boundaries of traffic separation schemes. The navigator should also assess the state of preparedness of the vessel for the passage, that is for the time of the intended transit, speed and engine readiness, method of steering and turning circles, preparedness for anchoring and manning levels, etc. and, with these factors in mind, decide on a safe distance at which to clear the adjacent dangers.
This data is put onto the chart as a safety or ‘margin’ line spaced away from the danger by the estimated safe distance.
Common sense and experience must be relied upon here when estimating where to position the margin lines, as it is impracticable to draw a ‘contour’ line around every adjacent danger. Furthermore, it is extremely difficult to reproduce curved lines from the chart on a reflection plotter with any degree of accuracy and impossible on modern radars equipped with electronic lines. The purpose of this part of the passage-planning process is to identify clearly all the clear water that can be used safely by the vessel during a transit of the area. Naturally the intention is to maintain the course line, but unfortunately the seaways have to be shared with many other vessels and therefore one must be prepared to leave the course line should an anti-collision manoeuvre be required at any time.
The final stage of this navigation process is to draw in the course lines on the chart, taking care at all times to keep within the defined safe/clear water areas.
Read full chapter
URL:
https://www.sciencedirect.com/science/article/pii/B9780080977522000088
Marine radar is a radar that is mounted and used by ships at sea for collision avoidance and other uses. It is used to detect other ships at sea and any other land obstacles. It is one of the most important safety components at sea and near the shores. But like all radar systems, marine radar has its own limitations and errors. Below are some of the errors and limitations.
1. Index error: This is the difference between the actual range between two points on a map and the range detected by the radar. This error can be observed when the vessels seat abeam between two points.
2. Beamwidth error: When the radar beam from the vessels moves away from the vessel, the width of the beam tends to widen. This causes distortion of the objects being detected. This distortion error increases as the vessel moves further away from the vessel.
3. Attenuation error: Attenuation is caused by the absorption and subsequent scattering of the beam energy as it is transferred through the atmosphere. This usually leads to a significant reduction in the strength of the echo. Attenuation is more pronounced in instances where there are a high frequency and short wavelengths.
4. Double echoes: These happen when the radar signals bounce off some parts of the ship and back into the receiver.
5. Multiple echoes: Multiple echoes occur as a result of several reverberations of the echoes from a different ship and from own ship multiple times. The display screen may show more than two or three objects being detected.
6. Indirect wave error: When a radar beam is emitted from the vessel, it is supposed to travel in a straight line directly to the contact. However, there are instances where the beam falls into the sea and it is deflected further which makes it travel a longer distance than if it would have traveled in a straight line.
Limitations
1. Clutter: Radar signals are affected by clutter especially from the sea and those caused by rainfall. This is why clutter controls are provided. However, the clutter controls need to be used with great caution because they may end up suppressing weaker objects that are navigating within the clutter zone.
2. Blind/Shadow sectors: The structure of the ship and sometimes the objects on the ship may cause blindness or shadow sectors on the ship. For this reason, it is important to properly mark the shadow or blind sectors in order to let other users understand the limitations of these sectors.
3. Distorted coastline: When a vessel is approaching a straight coastline, the radar may report a curved coastline or vice versa. This is because of the distance the radar takes to reach and return to the receiver from areas that are further away from the centerline of the vessel.
4. Input limitations: There are a number of sources that are used to feed information into modern radars. Some of these sources include GPS and compasses. These inputs may also have their own limitations that may have an effect on the radar itself. Ship navigators should be aware of these input limitations so as to understand their effect on the radar.
5. Heading misalignment: Heading markers are usually manually set on the radar on a vessel. This means that the markers may end up being misaligned for one reason or the other. To ensure the heading marker is not misaligned, you will need to point two vessels directly at each other. Ensure they are at a safe range. Once you have the vessels at this position, take the bearing of your vessel using a compass. The heading marker needs to correspond to this bearing.
6. Bearing discrimination: The radar set on the vessel needs to be able to distinguish between two different targets of the same range but with slightly different bearings. The radar is not able to discriminate and differentiate between these two contacts and may report as the same.
Learn More
Check out the types of radars uses in ships here.
Navigation VI
STCW Table A-II/1
RADAR NAVIGATION
What is RADAR?
The word radar is an abbreviation for Radio Detection And Ranging
Radar is an electromagnetic systems used for detection and location of
objects such as aircraft, ship, vehicles, people, natural environment etc.
The Use of Radar in Navigation
Interpretation of the Radar Picture
The radar picture is a plain picture of the ships surroundings. Only long
training and experience can teach you to interpret the radar picture quickly
and accurately as well as to identify different targets.
Use of radar to assist in navigation can be divided into 3 categories:
-Making Landfall
-Coastal Navigation
-Pilotage
LANDFALL NAVIGATION
Landfall by radar may give surprises. Always remember: initial radar fixes
are often not reliable at long ranges and when approaching land the picture
may change completely.
COASTAL NAVIGATION
Coastal navigation requires experience and vigilance all the time. The
range accuracy of the radar is generally better than the bearing accuracy.
When bearings has to be taken, choose isolated targets of relative small
size.
PILOTAGE
For navigation in narrow waters, radar is great device. The navigator must
know radar shadows. Knowledge is essential in order to distinguish clearly
between stationary and moving objects.
Fundamental Principle of Radar
Transmitter generates and transmits electromagnetic wave (sine or pulse).
A portion of it is reflected back by the target (object you want to identify).
The radiated portion is collected by the radar antenna and processed.
One antenna can be used for both transmission and reception
RADAR— derived from the phrase RADIO DETECTION AND RANGING.
A short burst of electro-magnetic energy transmitted and hit to an object
and then return, since the velocity of the propagation is known it would be
easy to calculate because the distance to the object as long as it can
measure time from which the transmission started until the echo return.
Fundamental Principle of Radar
On Board Ship the RADAR has two main tasks:
-To function as an aid to prevent collision, as with the help of RADAR one
can “SEE” in fog and darkness.
-To assist in navigation, particularly at landfalls and when navigating in
coastal waters.
Fundamental Principle of Radar
RADIO WAVES- are Electro magnetic Waves motion consist of crest and
trough.
Wavelength— is a distance between a successive crest of waves,
electromagnetic waves of a length between 0.1-30000 mm are known as
radio waves.
Frequency- are other way of measure of waves motion, which indicates
the number of crest that pass a fix of initial time.
Frequency and Wavelength are two terms closely associated.
Marine Radar Component
RADAR ANTENNA
Transmit and receive in an concentrated beam and a motor turns the
antenna in rotation, the signal, which are amplified the signal becomes
visible to the operator in form of a radar picture.
Two types of RADAR ANTENNA:
RECEIVER
The incoming signal is fed to a series of amplifier and further to detect or
demodulator for which smoothen the signal, the main task of the receiver is
to amplify the reflected (incoming echoes) weak echoes and make them
suitable for transmission to the indicator.
TRANSMITTER
It is the trigger pulses to the modulator and converted the inputs into a high
frequency oscillation thru magnetron. A high frequency oscillation are fed
via wave guide or into a coaxial cable to the transmitter/receiver switch.
DISPLAY
A radar echoes are display in a cathode ray tube (CRT). Several types of
CRT are utilized like A-SCAN or Short Persistent Tube, Plan Position
Indicator or PPI, Raster Scan Display.
A-SCAN or short persistent tube, the strength of an echo derived from its
amplitude.
P.P.I DISPLAY
PPI is a long persistent tube, the trace is rotated around in unison with the
rotation of the scanner and echoes previously recorded are retained during
a period of at least one scanner revolution.
RASTER SCAN DISPLAY. Normally a rectangular screen with dimension
in the ratio 4:3 consisting of; example 1024 horizontal lines and 1280
vertical line or picture elements (pixel)
The radar provides all echoes information in Cartesian form (i.e. range,
bearing). Before the information can be displayed the information must be
recalculated into X-Y coordinated by a processor.
The advantage of raster scan is that, it can be viewed in daylight without a
visor, and the capacity for the additional graphic information is almost
unlimited compared with the PPI.
The disadvantage of the raster scan is that even the best raster scan
display available today, cannot match the resolution of the old PPI.
Factors External to the Radar Set Affecting Detection
RADAR SCAN & RADAR SWEEP
Radar Scan— it is a one complete 360 degrees rotation of the antenna
(during one scan normally thousand sweeps are generated and
transmitted)
Radar Sweep— is the transmission of one radar pulse only.
PULSE REPETITION FREQUENCY (PRF)
Define as the number of pulses transmitted per second.
Long pulse is equals to low PRF
Short pulse equals to high PRF
LONG PULSE- means more power and longer range but less resolution in
range.
SHORT PULSE- means a weaker pulse, less radar range but better
resolution in range.
RADAR RANGE DEPEND MAINLY IN DIFFERENT PARAMETERS
Vertical Beam Width
Selected Pulse Length
Height of Antenna
Installation of Antenna
Ship’s Trim
IMPORTANT RADAR RANGE PARAMETERS
Antenna Height
Height of the Target
Size of the Target
Target Reflecting Area
Materials of the Target
Shape of the Target
Weather Condition
FOLLOWING PARAMETERS MUST BE TAKEN INTO ACCOUNT:
Transmitted Peak Power
Wavelength
Pulse Length
Antenna Gain
Noise Figure
Number of Pulses Per Scan
Wave Guide Loss
Display Parameters
RANGE DISCRIMINATION
The ability of radar to discriminate between two small object close together
in the same bearing.
Effecting range discrimination are:
Select Pulse Length
The size of the spot
If possible short pulse and short range should be selected and focused,
brightness carefully adjusted.
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Closed
agrajaghh opened this issue
Aug 27, 2014
· 17 comments
Closed
Invalid header marker
#1122
agrajaghh opened this issue
Aug 27, 2014
· 17 comments
Comments
Since the update to 2.0.0.65 I’m getting these errors/warnings:
Message
remote file duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes is listed as Verified with size 0 but should be -1, please verify the sha256 hash ""
Message
No hash recorded for duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes, performing full verification
Retry (5x)
Operation Get with file duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes attempt 1 of 5 failed with message: Invalid header marker
System.Security.Cryptography.CryptographicException: Invalid header marker ---> System.IO.InvalidDataException: Invalid header marker
bei SharpAESCrypt.SharpAESCrypt.ReadEncryptionHeader(String password)
bei SharpAESCrypt.SharpAESCrypt..ctor(String password, Stream stream, OperationMode mode)
bei Duplicati.Library.Encryption.AESEncryption.Decrypt(Stream input)
bei Duplicati.Library.Encryption.EncryptionBase.Decrypt(Stream input, Stream output)
bei Duplicati.Library.Encryption.EncryptionBase.Decrypt(String inputfile, String outputfile)
bei Duplicati.Library.Main.BackendManager.DoGet(FileEntryItem item)
--- Ende der internen Ausnahmestapelüberwachung ---
bei Duplicati.Library.Main.BackendManager.DoGet(FileEntryItem item)
bei Duplicati.Library.Main.BackendManager.ThreadRun()
Result
Warnings: [remote file duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes is listed as Verified with size 0 but should be -1, please verify the sha256 hash "", remote file duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes is listed as Verified with size 0 but should be -1, please verify the sha256 hash ""]
Errors: [Failed to process file duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes => Invalid header marker]
The file duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes doesn’t exist on my remote storage (WebDAV).
I didn’t had any problems with 2.0.0.60. What could be the cause? Should I create a bugreport?
There was a case where a file could be registered as being uploaded, when it had not been uploaded correctly.
Version 2.0.0.65 fixes this issue, and also finds all cases where this bug was triggered.
You say that the file does not exist on the remote storage?
But the output says that the file was found with size=0 ?
From the commandline, you can figure out what relies on that particular file:
Duplicati.CommandLine.exe affected webdav://abc/ duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes
This should give you a list of filesets that are affected.
You can then remove the filesets:
Duplicati.CommandLine.exe delete webdav://abc/ --version=1,3,5 --no-auto-compact
Finallly purge the files
Duplicati.CommandLine.exe compact webdav://abc/
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The affected command doesn’t find any files:
C:UsersUSERDesktopduplicati>Duplicati.CommandLine.exe affected "webdavs://webdav.mediencenter.t-online.de/folder?auth-username=user&auth-password=pass" duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes
A total of 0 file(s) are affected (use --verbose to see filenames)
Found 0 related log messages (use --verbose to see the data)
And yes, you are right, the file exists but the size is 0, I don’t know why I didn’t find it last time…
If no files are affected, the compact command should wipe the unused files.
Can you try that?
2014-08-28 10:36 GMT+02:00 agrajaghh notifications@github.com:
The affected command doesn’t find any files:
C:UsersUSERDesktopduplicati>Duplicati.CommandLine.exe affected «webdavs://webdav.mediencenter.t-online.de/folder?auth-username=user&auth-password=pass» duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes
A total of 0 file(s) are affected (use —verbose to see filenames)Found 0 related log messages (use —verbose to see the data)
And yes, you are right, the file exists but the size is 0, I don’t know
why I didn’t find it last time…—
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#1122 (comment)
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No its not working 
C:UsersUSERDesktopduplicati>Duplicati.CommandLine.exe compact "webdavs://webdav.mediencenter.t-online.de/folder?auth-username=user&auth-password=pass"
Enter encryption passphrase: ********
Compacting not required
I am guessing that you are somehow reaching an empty database.
Can you try the affected command with the parameter
—dbpath=path-to-database ?
2014-08-28 10:58 GMT+02:00 agrajaghh notifications@github.com:
No its not working
C:UsersUSERDesktopduplicati>Duplicati.CommandLine.exe compact «webdavs://webdav.mediencenter.t-online.de/folder?auth-username=user&auth-password=pass»
Enter encryption passphrase: ********
Compacting not required—
Reply to this email directly or view it on GitHub
#1122 (comment)
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yes, the dbpath helped. But I thought it should be determined automatically now from the webdav url?
I’m getting this output:
The following filesets are affected:
0 : 27.08.2014 22:42:37
1 : 25.08.2014 14:36:05
2 : 24.08.2014 19:28:06
3 : 22.08.2014 16:32:24
4 : 22.08.2014 11:07:01
5 : 21.08.2014 01:15:28
6 : 21.08.2014 01:00:00
7 : 21.08.2014 00:00:00
8 : 16.08.2014 14:24:45
The following files are affected:
C:UsersUSERDropboxUniProjektarbeitScansCarlsson - Comprehensive composite materials5.06aus pdf extrahiert.rar
Found 1 related log messages (use --verbose to see the data)
should I really delete backup 1-8? There is no other possibility? What would happen to the file mentioned?
The verbose output looks like this:
https://gist.github.com/agrajaghh/9b0dcbe693c2e480a8f3
You will not be able to restore that file, since the contents are not
reachable.
You can restore other files from the backup, but Duplicati will refuse to
run more backups on top of the damaged files.
If you have that file (as it would appear), you can also try to
rename/delete the remote file and then run repair.
It will then attempt to re-create the dblock file. This procedure will only
succeed if the local data is present.
Otherwise, yes, you need to erase those filesets for the backups to
continue.
There is currently no «healing» method to recover automatically from this
situation.
2014-08-28 13:20 GMT+02:00 agrajaghh notifications@github.com:
yes, the dbpath helped. But I thought it should be determined
automatically now from the webdav url?I’m getting this output:
The following filesets are affected:
0 : 27.08.2014 22:42:37
1 : 25.08.2014 14:36:05
2 : 24.08.2014 19:28:06
3 : 22.08.2014 16:32:24
4 : 22.08.2014 11:07:01
5 : 21.08.2014 01:15:28
6 : 21.08.2014 01:00:00
7 : 21.08.2014 00:00:00
8 : 16.08.2014 14:24:45The following files are affected:
C:UsersUSERDropboxUniProjektarbeitScansCarlsson — Comprehensive composite materials5.06aus pdf extrahiert.rarFound 1 related log messages (use —verbose to see the data)
should I really delete backup 1-8? There is no other possibility? What
would happen to the file mentioned?The verbose output looks like this:
https://gist.github.com/agrajaghh/9b0dcbe693c2e480a8f3—
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#1122 (comment)
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Okay, I renamed duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip and tried to run repair:
C:UsersUSERDesktopduplicati>Duplicati.CommandLine.exe repair "webdavs://webdav.mediencenter.t-online.de/folder?auth-username=USER&auth-password=pass" --dbpath="C:UsersUSERAppDataRoamingDuplicatiADAWFAVLKM.sqlite"
Enter encryption passphrase: ********
Listing remote folder ...
Repair cannot acquire 357 required blocks for volume duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes, which are required by the following filesets:
duplicati-20140816T122445Z.dlist.zip.aes
duplicati-20140820T220000Z.dlist.zip.aes
duplicati-20140820T230000Z.dlist.zip.aes
duplicati-20140820T231528Z.dlist.zip.aes
duplicati-20140822T090701Z.dlist.zip.aes
duplicati-20140822T143224Z.dlist.zip.aes
duplicati-20140824T172806Z.dlist.zip.aes
duplicati-20140825T123605Z.dlist.zip.aes
duplicati-20140827T204237Z.dlist.zip.aes
This may be fixed by deleting the filesets and running repair again
Failed to perform cleanup for missing file: duplicati-beb8f93c067464d2dacd83e45b8ab2084.dblock.zip.aes, message: Repair not possible, missing 357
blocks!!! => Repair not possible, missing 357 blocks!!!
So the only possibility is to erase those filesets?
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I forgot to mention that the local file is still present and I didn’t change it
It is strange that the «affected» command says it is only a single file
that is affected by that dblock file, yet the repair is missing 357 blocks.
How large is the file?
How large is each volume?
Are you using —store-metadata=true?
Regards, Kenneth
2014-08-28 14:06 GMT+02:00 agrajaghh notifications@github.com:
I forgot to mention that the local file is still present and I didn’t
change it—
Reply to this email directly or view it on GitHub
#1122 (comment)
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The affected .rar file is 81,4MB
The dblock.zip.aes files are 35M
The default blocksize is 100kb, no? So that would make sense I guess…
I’m not using --store-metadata, I just put these options:
--throttle-upload=20000 (which is still not working for me)
--snapshot-policy=on
--usn-policy=on
I think, the same or a similar problem occurs here (Win7 x64, local drive):
After deleting the local database and executing «repair» in Browser UI, I get the message `Error while running Daten: Ein Eintrag mit dem gleichen Schlüssel ist bereits vorhanden.´ and lots of following messages in the log:
Failed to process index file: duplicati-ifef207c4eada47b0b37a5f378af1736c.dindex.zip
System.Exception: Unexpected number of remote volumes detected!
bei Duplicati.Library.Main.Database.LocalDatabase.UpdateRemoteVolume(String name, RemoteVolumeState state, Int64 size, String hash, IDbTransaction transaction)
bei Duplicati.Library.Main.Operation.RecreateDatabaseHandler.DoRun(LocalDatabase dbparent, IFilter filter, NumberedFilterFilelistDelegate filelistfilter, BlockVolumePostProcessor blockprocessor)
Next I execute:
C:Program FilesDuplicati 2>duplicati.commandline.exe verify F:backup2daten --no-encryption=True --dbpath=C:UsersMartinAppDataRoamingDuplicatiQQXLCPXUX Y.sqlite
That results in following message
Listing remote folder ...
remote file duplicati-bba54495259b44a9f8ac65b2ac0875cf9.dblock.zip is listed as Uploaded with size 183954469 but should be -1, please verify the sha256 hash ""
remote file duplicati-bf802c134190244a086e3f3378648804a.dblock.zip is listed as Uploaded with size 202351250 but should be -1, please verify the sha256 hash ""
Ein Objekt kann nicht von DBNull in andere Typen umgewandelt werden.
Then I execute:
C:Program FilesDuplicati 2>duplicati.commandline.exe affected F:backup2daten duplicati-bba54495259b44a9f8ac65b2ac0875cf9.dblock.zip --no-encryption=True -- dbpath=C:UsersMartinAppDataRoamingDuplicatiQQXLCPXUXY.sqlite --verbose
The results are:
Input command: affected
Input arguments:
F:backup2daten
duplicati-bba54495259b44a9f8ac65b2ac0875cf9.dblock.zip
Input options:
no-encryption: True
dbpath: C:UsersMartinAppDataRoamingDuplicatiQQXLCPXUXY.sqlite
verbose:
A total of 0 file(s) are affected (use --verbose to see filenames)
Found 0 related log messages (use --verbose to see the data)
Compacting doesn’t do anything:
C:Program FilesDuplicati 2>duplicati.commandline.exe compact F:backup2daten --no-encryption=True --dbpath=C:UsersMartinAppDataRoamingDuplicatiQQXLCPXU
XY.sqlite
Compacting not required
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I updated from 2.0.0.57 to 2.0.0.65 on another machine and got similar warnings:
Warnings: [remote file duplicati-b219dd0212f8b4589ad9e98c7848c35a1.dblock.zip.aes is listed as Verified with size 20913390 but should be -1, please verify the sha256 hash "", remote file duplicati-i749e0624dfa94e12bf4aa6d86ce2bfce.dindex.zip.aes is listed as Verified with size 7838 but should be -1, please verify the sha256 hash "", remote file duplicati-b53195613c7b74fa89fd1f068a420fd6f.dblock.zip.aes is listed as Verified with size 0 but should be -1, please verify the sha256 hash "", remote file duplicati-b6f034e4a3eee4f09ac5c458abfc700f2.dblock.zip.aes is listed as Verified with size 0 but should be -1, please verify the sha256 hash "", remote file duplicati-b50bb18b0febe4109b23e923e9fb80261.dblock.zip.aes is listed as Verified with size 0 but should be -1, please verify the sha256 hash "", remote file duplicati-i749e0624dfa94e12bf4aa6d86ce2bfce.dindex.zip.aes is listed as Verified with size 7838 but should be -1, please verify the sha256 hash ""]
I guess this is the same issue?
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I tried to create a new backup job with the same backup location and run repair, but I got this error:
Failed: SQL logic error or missing database
near "VALUE": syntax error
Details: System.Data.SQLite.SQLiteException (0x80004005): SQL logic error or missing database
near "VALUE": syntax error
bei System.Data.SQLite.SQLite3.Prepare(SQLiteConnection cnn, String strSql, SQLiteStatement previous, UInt32 timeoutMS, String& strRemain)
bei System.Data.SQLite.SQLiteCommand.BuildNextCommand()
bei System.Data.SQLite.SQLiteDataReader.NextResult()
bei System.Data.SQLite.SQLiteDataReader..ctor(SQLiteCommand cmd, CommandBehavior behave)
bei System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
bei System.Data.SQLite.SQLiteCommand.ExecuteNonQuery(CommandBehavior behavior)
bei Duplicati.Library.Main.Database.LocalRecreateDatabase.UpdateBlock(String hash, Int64 size, Int64 volumeID, IDbTransaction transaction)
bei Duplicati.Library.Main.Operation.RecreateDatabaseHandler.DoRun(LocalDatabase dbparent, IFilter filter, NumberedFilterFilelistDelegate filelistfilter, BlockVolumePostProcessor blockprocessor)
bei Duplicati.Library.Main.Operation.RecreateDatabaseHandler.Run(String path, IFilter filter, NumberedFilterFilelistDelegate filelistfilter, BlockVolumePostProcessor blockprocessor)
bei Duplicati.Library.Main.Operation.RepairHandler.RunRepairLocal()
bei Duplicati.Library.Main.Operation.RepairHandler.Run()
bei Duplicati.Library.Main.Controller.<Repair>m__1(RepairResults result)
bei Duplicati.Library.Main.Controller.RunAction[T](T result, String[]& paths, Action`1 method)
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I’m still getting these errors when I try to run the backup after creating the job and running repair:
remote *.dblock.zip.aes is listed as Uploaded with size 36651678 but should be -1, please verify the sha256 hash ""
edit: running version 2.0.0.74
log:
26.11.2014 20:23:23
Message
Fatal error
System.InvalidCastException: Ein Objekt kann nicht von DBNull in andere Typen umgewandelt werden.
bei System.DBNull.System.IConvertible.ToInt64(IFormatProvider provider)
bei Duplicati.Library.Main.Database.LocalTestDatabase.RemoteVolume..ctor(IDataReader rd)
bei Duplicati.Library.Main.Database.LocalTestDatabase.<SelectTestTargets>c__Iterator0.MoveNext()
bei System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
bei System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
bei Duplicati.Library.Main.Operation.TestHandler.DoRun(Int64 samples, LocalTestDatabase db, BackendManager backend)
bei Duplicati.Library.Main.Operation.BackupHandler.Run(String[] sources, IFilter filter)
26.11.2014 20:23:23
Message
remote file duplicati-ba63ffd473e87418a88537d24e4d7f543.dblock.zip.aes is listed as Uploaded with size 36606206 but should be -1, please verify the sha256 hash ""
26.11.2014 20:23:23
Message
remote file duplicati-b578ade40253c4892a3ed576b3a64a8ba.dblock.zip.aes is listed as Uploaded with size 36651678 but should be -1, please verify the sha256 hash ""
26.11.2014 20:23:23
Message
removing file listed as Temporary: duplicati-ib97e9f6459114025be72bc3fc33ba915.dindex.zip.aes
26.11.2014 20:23:22
Message
removing file listed as Temporary: duplicati-b6b4c09db1cec491fa62877fe9d28d2d4.dblock.zip.aes
26.11.2014 20:23:13
Message
Deleted 22 files, which reduced storage by 316,76 MB
26.11.2014 20:22:51
Message
Compacting because there are 11 fully deletable volume(s)
26.11.2014 20:22:51
Message
Deleted 8 remote fileset(s)
26.11.2014 20:22:42
Message
Deleting 8 remote fileset(s) ...
26.11.2014 20:20:58
Message
remote file duplicati-ba63ffd473e87418a88537d24e4d7f543.dblock.zip.aes is listed as Uploaded with size 36606206 but should be -1, please verify the sha256 hash ""
26.11.2014 20:20:58
Message
remote file duplicati-b578ade40253c4892a3ed576b3a64a8ba.dblock.zip.aes is listed as Uploaded with size 36651678 but should be -1, please verify the sha256 hash ""
26.11.2014 19:18:03
Result
VerboseOutput: False
VerboseErrors: False
Messages: []
Warnings: []
Errors: []
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seems to be fixed with 2.0.0.76 👍
Principle: it Works on Echo Principle (Echo ranging by radar) which is based on a time interval between the transmission of an EM pulse into the environment and reception of its echo.
Type Of Radars:
- Indirect Echo (reflected): Range true but bearing of a vessel in direction of the obstruction. (mast, funnel or containers on a container ship)
- Multiple Echo: Bounce of energy back and forth, entering antenna in each bounce. . . .
- Side Lobes: Leakage in energy
- Radar to radar interference: Transmission of other radar picked up by our radar.
- Second Trace Echoes: A sent no return, B sent–A return
Radar Limitations:
- Range Discrimination: Same Bearing different range, the ability of the RADAR set to clearly distinguish two small targets on the same bearing at slightly different ranges. The distance between the two targets is equal to or less than ½ PL.
- Bearing Discrimination: 2 targets on the same range but different bearing, separated by 2.5° d, the ability of the radar set to clearly extinguish two target of the same range and slightly different bearings. (Factor affecting bearing discrimination: High Beam Width)
- Minimum Range:
- Blind/Shadow sectors: Ship structure such as Mast or funnel might create a blind sector.
Ground Stabilization and Sea Stabilization:
Related Questions:
- Radar Range and Bearing Accuracy:
→ Range Within 30m or 1% of the range scale in use (whichever is greater);
→ Bearing within 1 degree. - How to check the performance of radar?
→ By “Performance Monitor” instruction in the user manual - How often?
→ After start-up and once every watch - Radar Availability:
→ Fully functional within 4 minutes after switching on.
→ Fully operational within 5 seconds from standby condition. - What is Radar Stabilized? – When getting Heading input from the gyro.
- What happens if Gyro fails or Gyro input lost? – The radar will go into “HEAD-UP Orientation”
Radar Setup for Collision Avoidance:
- Relative Motion: Helps is maintaining situational awareness.
- CU / NU—I prefer CU, as the screen and outside of window view remain the same.
- True trail: To get the true aspect of a vessel
- Relative vector: To see the relative line of approach.
- Speed through LOG Sea stabilization mode.
Radar Startup & Setup:
- Check scanner for any obstruction (Halyard, working aloft, any notice near radar screen)
- Switch on radar (do setting till its warming up [What happens in warmup and how much time?])
- Select orientation, motion check heading and speed input (from were heading and speed input)
- Once you see Standby on-screen, Press “TRANSMIT”
- Select Range, Pulse length.
- Check Heading marker is aligned with the fore-and-aft line of the vessel.
- Adjust (B-G-T-R-S)
Brilliance: Such that clearly visible and do not hurt your eyes.
Gain: Such as you can see fine speckles on screen. (What Gain does?)
Tunning: Such that targets are best seen on screen (What Tunning does?)
Rain: Only use this if it’s raining. (Always use before Sea clutter, but WHY?)
Sea: If required in bad weather. - Check Radar Performance by “Performance Monitor” (What is it?)
Thank you, do you have any questions related to Radar and Arpa? Let me know.