This is not a problem with mkgmap, just a curious thing with Mapsource/Basecamp.

 

Recently I decided to increase the symbol size I used for my maps for POI from a base 16x16 to 24x24. After finding a site where I could download all the PNG files for Mapnik style OSM sysmbols from sizes 12x12 to 64x64 I got to work losing a good couple of weekends in the process; converting the PNGs to be used in my TYP file editor, and tidying up the symbols. Once done I was delighted with the results, but then scrolling around the map I found parts of it were no longer being displayed in Mapsource or Basecamp. I tried the map on my Dakota 20 and could not find the same problem there.

 

One common thing with the missing map parts was it always seemed to be where power lines started to come together, I had changed the image for power towers from a 7x7 pixel image (TYP: 0x6417) to a 22x19 pixel image  (TYP: 0x640E). Playing with the detail level in Mapsource I found that viewing on Medium detail level; where the power towers were visible, created a hole in the map where nothing in the rectangle was shown. But changing to the Low detail level when the power towers were lost the map was fine again. It does not seem to be the number of POIs either as the centre of St Albans was shown fine with many POIs. Although these were many different POIs not the same.

 

I am at a loss why large POIs (or at least power power ones) are causing these “holes” in the map, but simply changing the power tower level from 1 to 0 in the style file has fixed the problem as far a I have seen.

 

I have attached two JPEGs showing the difference between the two detail level settings when the power tower was still defined at level 1 in the points file.

 

If anyone has any thoughts I would like to hear them.

 

Regards, Geoff