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TOPIC: Showing images with depth overlays on an HDS

Showing images with depth overlays on an HDS 5 years 11 months ago #1953

  • Matt
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Lowrance HDS and Elite HDI units can show images of any sort as part of a map, and combining a background image with a vector overlay to show depths can produce great maps that can be really useful in fishing situations. The sort of images you might want to be able to see your on unit include satellite imagery, scanned topographic maps, sidescan image mosaics etc.

In this example we are going to combine a side-scan mosaic image created by DrDepth (ReefMaster doesn’t do side-scan mosaics yet – but it’s coming soon!) with a vector overlay created in ReefMaster.

1. Create the raster background files
The Insight Map Creator from Navico can be used to create raster backgrounds for your unit, using any geo-calibrated image that you can provide with a KML or PGW calibration file (KML is a commonly used file format native to Google Earth, and many tools exist that will convert geo-calibrated files in other formats, e.g. geoTIFF, to KML).

We are using a side-scan image mosaic that has been exported from DrDepth as a PNG image file with an associated Google Earth KML file.

Start the Navico Insight Map Creator application, and switch to raster mode.
We need to let the IMC know which files to process. Note that the IMC accepts folders for raster mode (not individual filenames), and will process all image files within the specified folder(s), so the easiest thing to do is make a new folder which contains just the KML and image files.

Set an appropriate min and max resolution:


The Min and Max Resolution values refer to pixels per metre of your original image. The IMC will rescale your image to match the values you use. To determine the native resolution of your image, divide the width in pixels by the width in metres. You can find the width in pixels by right-clicking the image in Windows explorer and looking at the properties. It is not necessary to a value as low as your native resolution, but you will lose some detail from your image at higher zoom levels if you do not. Note that very high resolution images (with low pixels-per-metre value) can take a long time to process. The upper limit is a matter of preference – the higher the value, the lower the zoom level required to see the image in the unit. The downside is that the image will be set in a “tile” that will obscure other map components, and this tile will cover larger areas at higher resolution settings. A value of 8 is a good starting point.

Set your work directory, and click Build

Once the build completes, there will be some output files in a directory called "BoundAT5s" sitting underneath the specified build directory. These images should be copied to a map card in a directory called "ShadedRelief" located at the root of the card.

2. Create the vector overlay.
Generate the map project of the area in Vector mode. Vector mode is important here if we want to see areas coloured by depth in the finished map. We cannot use a raster background, as that would obscure the image background that we exported in step 1.



Choose an AT5 compatible palette now (unless you want to style the map areas individually in the user map) and select the right-click-menu option Add components to map.../Add components…/New User Map.



Here, the background image that we have already processed in the IMC has also been imported into ReefMaster (option New Image, and select the KML file – not the image file). This helps us see how the finished map will look on the unit, but is not required as part of this map create process.

Set the transparency of the depth areas
All we need to do to this map before exporting it is to set the transparency of the depth areas, so that we will be able to see the background image through the coloured depth areas in the GPS unit. Choose a value for the opacity field, where 1 is fully transparent and 255 is fully opaque, and export the map from ReefMaster by right-clicking in the user map view and selecting the option Write to File. Make sure that the option “Export Raster background” is not selected, as we do not want to overwrite our existing background image, and click save and select the root of your memory card as the save location.

This is how the map looks on a Lowrance HDS 5. We now have the best of both worlds – a background image showing features on the bottom, and depth area colours on top.





Note that if we want, we can turn the coloured depth areas on and off using the Chart Categories feature on the unit. We can do this whilst on the water, whilst keeping the depth contours visible (these can also be turned off, if required). The category for depth areas exported by ReefMaster is (AREA)Nautical/Depth.





In this example the style of the contours in the user map has been changed to make them thicker and more visible over the background image (the width and colour attributes of the Major Contour group in the user map).

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Showing images with depth overlays on an HDS 5 years 11 months ago #2007

  • Fishton
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This is some really great stuff.
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Showing images with depth overlays on an HDS 5 years 10 months ago #2137

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I am on day 3 now and I cannot achieve this.
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Showing images with depth overlays on an HDS 5 years 10 months ago #2146

  • Matt
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John,

Happy to talk this through with you or take a look at your vector exports to see what is going on - export as Shapefile and send through via email.

For this to work, the key points are:
  • You must create isobaths in vector mode to get depth areas.
  • You need to create an intermediary User Map to edit the areas before export, and colour the depth areas in the user map.
  • You must create the raster background separately and just add the two RM generated at5 files to the root of the card (not the generated shadedrelief folder).

Matt
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Showing images with depth overlays on an HDS 5 years 10 months ago #2147

  • Fishton
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How do I create isobaths in vector mode, and where do I find vector mode in RM 1.6?
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Showing images with depth overlays on an HDS 5 years 10 months ago #2148

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It's the default in a map project in v1.6 - you have to actively revert to raster mode by using the Colour mode button in the map project properties.
If you can post what you've got and where it is going wrong I sure we can get it working pretty quickly.

Also another thing to check is that you don't have an filled shoreline underneath the isobaths that is blocking your raster, although from the way you described the problem earlier it didn't sound as if that was happening.

Matt
Last Edit: 5 years 10 months ago by Matt.
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Showing images with depth overlays on an HDS 5 years 10 months ago #2149

  • Fishton
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This is what I am doing ...
1. Open RM
2. Open Recent Workspace (.rmdb file)

3. Region Select from Global View

4. Add tracks to project 'Inanda01'
5. Define Map Boundary

6. Contour View of 'Inanda01'

7. Create shoreline - Map Boundary
8. Apply interval settings (Map Settings)
9. Add to map - Isobaths - New User Map ... InandaISO1

10. Custom Isobath depth colours and change opacity to 100 to allow background image to show through.

11. Export Map to GPS (Inanda01 Tab)

12. Create Shapefile for At5 IMC format

13. Save file to IMC vector folder

14. Build At5 with IMC

15. Copy file 'Large.at5' from IMC Output Folder (BoundAT5's)

16. Paste to SD card - my SD card already had the Raster image files saved under the folder ShadedRelief.

17. Insert into Lowrance HDS
18. The ShadedRelief Background chart can be see (sediment chart),

but something is not right with the contours

and there are no isobaths ...
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Showing images with depth overlays on an HDS 5 years 10 months ago #2150

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John,
First up - you are using the old 1.6 beta, no the new version 1.6 which you should download and install (not an automatic upgrade) from the try page. You should do this first, as the release version has some improvements - although there are no major functional differences that would stop this working.
  • You absolutely need the at5.xml file on your card for transparency to work - this is what this file is for, so make sure you copy that as well. If you do an automated at5 export from RM and select the root of your SD card as the destination, this is taken care of for you (just ensure that you de-select "export raster" when exporting the user map, or copy your raster files over afterwards - otherwise they will be overwritten). If you are not doing an automated AT5 generate, then you need to check the auto create at5.xml option in the IMC.
  • You should be exporting your user map, not your map project.
  • You might consider losing the shoreline which is a filled polygon for the water body. This is shown behind your isobaths by default, and once you get the vector overlays going you will probably find that it obscures your raster. Just go to the shorelines group in the user map and delete the contents of the list (or set opacity/colour to whatever you want).
Last Edit: 5 years 10 months ago by Matt.
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Showing images with depth overlays on an HDS 5 years 10 months ago #2158

  • Fishton
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1 - updated software
2 - there is no at5.xml file - where does this file come from and where will I find it?
3 - how do I do an automated at5 export from RM?
4 - I am now exporting the user map
5 - I have removed the shoreline entirely

I now have contours on my shaded relief, but still no isobaths




If I change to 2D, then I get this ...

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Showing images with depth overlays on an HDS 5 years 10 months ago #2159

  • gpiverson
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AT5.xml is generated when the Advanced Options > Vector Options > Auto Create XML is checked. The file will be placed in the BoundAT5s folder and must be copied to the root folder of the card.

This file can only be created when running the Vector Processing Mode.
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Showing images with depth overlays on an HDS 5 years 10 months ago #2160

  • Matt
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John,
Automated AT5 export is under the Lowrance export option - see updated v1.6 manual pages for more. This option creates the IMC project file and runs it automatically. You just select the root of your SD card as the destination. There is an option to export a raster background - either depth colours or a "dummy" blank raster to allow opacity to work (AT5 quirk). You want to deselect this option as you have your own raster files already. Using the automated export will put both the large.at5 and at5.xml files in the right place.

If you want to use the IMC, you need to check the option "Auto create xml" as shown below. This creates the at5.xml file and this file contains information about how to render polygons over raster - including opacity. I assumed you were using the auto at5 export, otherwise I would have mentioned this as a possible problem earlier (if I'd thought of it!). See the IMC documentation for more.



It looks like you have data that will work as is - you just need to create the at5.xml file - so the first thing I would do is just recreate your map using your existing files and checking the auto create xml option.

Matt

Edit to add: if you have a filled shoreline behind your isobaths, don't include that when you rebuild in the IMC as that may obscure the raster (or - delete it from the user map before doing an automated export).
Last Edit: 5 years 10 months ago by Matt.
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Showing images with depth overlays on an HDS 5 years 10 months ago #2161

  • Fishton
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gpiverson wrote:
AT5.xml is generated when the Advanced Options > Vector Options > Auto Create XML is checked. The file will be placed in the BoundAT5s folder and must be copied to the root folder of the card.

This file can only be created when running the Vector Processing Mode.

Boom!!! There it is, thanks. Amazing how such a small error can create utter disappointment and often the cause of many who try to just give up.

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