[ gpsdrive ] NOAA charts

[Hamish]

Chris wrote:
> Perhaps if Hamish has the time he could answere the
> following question. 

(I am traveling for some weeks so unlikely to even notice most emails)

> I would like to remove the white collars on the set of NOAA charts
> that I have for the Great Lakes and East Coast to allow them to be
> rendered in gpsdrive without the annoying white boarders. 
> 
> Ive install the lastest grass stable version and in the
> coming week will setup a dedicated work station to process
> charts.

I'd suggest working with version 6.4.0rc

> Check the grass archive and there are only two entries
> on this subject which I found strange.
 
maybe a post there would be helpful

> So was wondering is their a way to use grass and script it
> to process charts in a specific folder to remove the white
> collars but retain the georeferenced data.

most things are possible with existing tools, just requires knowledge
of the available tools and some imagination. 
perhaps r.reclass'ing white areas to NULL then 'g.region zoom=' to the
reclass map?


> The next step would be to process the same folder allowing the
> maps to be tiled

just a shell loop, no problem

> and then the final step is to import them into gpsdrive 

I'd suggest export as geotiff then running gdal_slice.sh for that.
d.out.gpsdrive is also an option, but that is better for one-off maps with
decorations I think. gdal_slice.sh has better built in tiling.

 
> Best regards and thanks for any info. If this is a pipe
> dream or not needed feel free to correct me.

I think it is rather do-able.

only issue may be teaching it to crop away text and little specks, not
just empty white areas. again I think it is possible, just needs some
imagination with the GIS tools & reclass step.


Hamish