[ gpsdrive ] Map formats

Bernhard D Rohrer graylion at sm-wg.net
Wed Sep 12 00:30:47 AKDT 2007


Hamish wrote:
#
> not yet, hopefully gpsdrive will get full GDAL support one day. This is
> planned.
> 
>
> the other method which is more flexible but less direct is to load the BSB
> charts into GRASS GIS (http://grass.itc.it) with the r.in.gdal module,
> then export to gpsdrive tiles using the d.out.gpsdrive module.
> 
> 
> I have noticed there is a problem when a projected (ie not lat/lon)
> regional scale map is cut up for gpsdrive with the gdalslice script, as
> north (up) in the projection may not be exactly in line with true north
> and so the map is slightly rotated. (only for 1:200000+, 1:50000 or finer
> is hard to spot) Some of my maps are perfect, others are way off. The
> above north rotation is my best guess right now, but I've not fully
> convinced myself of that.
> 
> So it's pretty good as a guide, but don't trust it yet to keep you away
> from a rock. Having said that I use gpsdrive to steer to my sampling
> stations (naut chart + waypoint overlay), and for those fine scale maps it
> works great.
>
does this problem also apply to the GRASS GIS method? The reason I am 
asking is that indeed this is what I hope to be able to use GPSdrive for 
- keep us and a 30m ex RN minesweeper off rocks and stuff.

thanks

Bernhard


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