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GPSMapEdit *.mp to*.img Detail Lost

Started by babj615, August 08, 2013, 08:52:46 AM

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Quote from: babj615 on August 09, 2013, 08:08:48 AM
I had looked at that page yesterday, and the example they give simply shows every other point being removed. I did not see anything in the Wikipedia article that equates to the cgpsmapper 0.1-10 scale.
See in "Pseudocode" section, there is used "epsilon" constant. My guess is that for cgpsmapper could be dependency like epsilon = 2.4m/value.


It is when you convert a track to a polyline, there is a checkbox for generalize.


Has anybody solved the problem with "loss of detail" after compiling by cgpsmapper?

I am asking, because I am facing the same problem with isobaths in waterways maps (web:

I thought, I solved the problem by using level0=26 instead of level0=24. The picture has been very nice in Mapsource, but the polygons and polylines haven't been visible (under certain zoom) in marine plotters.  So, this solution is unusable.


AFAIK cgpsmapper only supports to 24-bit.  My guess would be because Garmin devices only support coordinates to 24 bit.  Perhaps Garmin's newer devices support closer coordinates. 

See popej's Aug 8, 2013 11:41AM post.

The 'accuracy' of most publically available source data would not even support 24-bit coordinates.  Some calculations I did years ago indicated 23-bit is about equal to a scale of 1:20,000.   Most (likely none) consumer grade GPSr units used on the 'fly' would be accurate to 2.4m (7.9m) anyway.


I read the post from Popej and it is obvious not only from this post, that Popej knows about creating of maps much more than me. But ...

What does exactly mean "cgpsmapper only supports to 24-bit"? When I use level0=26, the is no error at the compilation and I can read in the log, that all object were succesfully imported into layer 0. And, as I wrote, the result in Mapsource is better than by using 24 bit (you can see isobaths in the same place with 24 bit and 26 bit in attachments).

Of course, the discussion about this is useless, because the map with 26 bit is not visible under ceartain zoom. Discussion is, how prevent cgpsmapper from distortion the lines.

SimplifyLevel doesn't help, because input data are correct and therefore I use Preprocess=N. Even when I used Preprocess=Y and SimplifyLevel=3, the picture was the same - distorted.

May be there is no way (see discusssion  at page

I understand that the precisison 2.4m is enough for GPS unit, but I don't think, that inaccuracy GPS unit is reason for making inaccurate maps.


Quote from: zhrd on September 08, 2013, 07:37:56 AMWhat does exactly mean "cgpsmapper only supports to 24-bit"?
It means that internal representation of coordinates is 24-bit integer. This is what we know about img format and what is written in cgpsmapper manual.

But you are right, cgpsmapper accept level0=26 and creates map, which probably uses better resolution. I don't know how compatible is that kind of map with Garmin devices. I have checked that simple, non-routable map can be displayed in Mapsource and BaseCamp.


I wrote about the 24 bit limits in this old thread. My solution was to use a raster-based (.kmz) map which does not seem to have this limit. Of course, the size of such a map is limited and marine devices don't support them at all.,1335.msg8387.html#msg8387