[ gpsdrive ] Nautical maps

[Hamish]

tartifola wrote:
> I've recently discovered gpsdrive and I like it very much.
> I would like to use it for sailing and after some search I was not
> able to find any reasonable nautical map? Any hints where to look
for?

what part of the world are you in?


For the USA, NOAA makes charts available in a number of raster formats 
(georeferenced??) or S-57 vector format. GDAL/OGR can read those for
transforming into gpsdrive tiles.
Also common for the US are BSB format raster charts (usually you buy
the CD of your part of the coastline), but beware that newer editions
may be encrypted for no other reason I can think of but pure corporate
greed.
GDAL can read those too. 

http://www.gdal.org/formats_list.html
http://www.gdal.org/ogr/ogr_formats.html

once you find something GDAL can read you have a number of ways to get
it into gpsdrive.

e.g. "gdal_slice.sh"
  http://hamish.bowman.googlepages.com/gpsdrivefiles#tiles
or via GRASS GIS's d.out.gpsdrive
 
http://grass.osgeo.org/grass63/manuals/html63_user/d.out.gpsdrive.html


take special care about the disclaimer about the software not coming
with any sort of guarantee and not intended to be used as a primary
means of navigation. The map scaling method is not as good as it could
be. I've had pretty good success using gpsdrive at sea with scanned
nautical charts as a backdrop, but sometimes a poorly registered map
showed us a few hundred meters out, on land. (gdal_slice method with ~
1:500,000 regional maps, I never tracked down where I went wrong
processing the data so I don't know if gdal_slice was to blame or not.
d.out.gpsdrive stuff was fine AFAIR)


Hamish



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