This is a tricky one Meggs. We actually set that background colour in the gradient relief export when generating that preset style. The reason we do it is because AT5 and transparency don't mix - we'd get black if we didn't use a colour. Land colour works (usually) because the water body is filled, and the land colour raster blends with land.
You could probably achieve what you want, but not by using a preset map export. You'd have to export the shaded relief by hand, which will have a transparent background, and then somehow either colour the background (combine it with an image of the same size of a single colour), or create a dummy background image and use that along with the shaded relief image when generating the AT5 raster in the IMC.
The latter method is probably easier:
- Create a small image using e.g. paint. Fill it in your required background colour and save it. The image must be smaller than the SR, as lower resolution images will be processed by the IMC to show behind higher resolution images. The image could be tiny - 10px square if you want.
- Make a copy of the .kml file that was saved when you exported the SR, and change the name of this copy to match your newly created "dummy" image.
- Open the kml copy in an editor such as notepad (you might need to right click/open with, to stop it opening in Google Earth) and edit the href tag (see below) so that it has the name of your dummy image file (full path is not required, so long as the kml and image files are in the same directory).
- Copy both your SR and dummy image and kml files to an empty directory, and run the IMC raster process on that directory. You will end up with a raster layer with your choice of coloured background. Your existing AT5.large should work fine over the top, so you only need to replace the contents of the ShadedRelief folder.
We might look at adding a background colour option for shaded relief export..
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom">
<GroundOverlay>
<name>American Lake</name>
<color>ffffffff</color>
<Icon>
<href>dummy.png</href>
<gx:altitudeMode>clampToSeaFloor</gx:altitudeMode>
<viewBoundScale>1</viewBoundScale>
</Icon>
<LatLonBox>
<north>47.142168884</north>
<south>47.1080779591</south>
<east>-122.533470272042</east>
<west>-122.590449009258</west>
</LatLonBox>
</GroundOverlay>
</kml>
