[Xastir] Re: topo maps

[Curt, WE7U]

On Mon, 1 Mar 2004, Matt Werner wrote:

> If it has the collar.  The images I have already have the collar removed,
> thus no coordinates.  I suppose I could manually look up the print versions
> of each map to see what the coordinates are supposed to be for my image, and
> then create a .fgd file for that image.

Those types of maps (let's call them bastardized DRG's, or BDRG's,
ok?), came out after I wrote the geotiff Xastir code.  The FGD
requirement came in because I was trying to crop off the white map
collar, and the info was not easily available any other way as to
where that collar/map border really was.


> Are the coordinates printed on the map collar the EXACT same thing used by
> xastir in the .fgd file, or does the .fgd file contain more accurate
> resolution of the corners?

Same.


> I have a digital image of the map with a collar (from a Maptech CD).  I
> can't seem to use the Maptech file as the map I want - they appear to be a
> proprietary format.  The Maptech map does show me the coordinates though.  I
> also have the MN DNR tif file of the same map, without the collar (or
> coordinates).

Yes, Maptech format is proprietary.


> I created a .fgd file by hand.  This is it:
>
> 1.5.1.1 WEST BOUNDING COORDINATE: -92.250000
> 1.5.1.2 EAST BOUNDING COORDINATE: -92.121666
> 1.5.1.3 NORTH BOUNDING COORDINATE: 47.000000
> 1.5.1.4 SOUTH BOUNDING COORDINATE: 46.871666

Looks fine to me.


> I think I'm making progress, but still have problems.  Is there more to an
> fgd file than just that?

Yes, but not that Xastir cares about.  You have the four lines that
Xastir wants.


> xastir says:
>
> No samplesPerPixel tag found in file, setting it to 1
> Problem in translating
> Problem in translating
> Problem in translating
> Problem in translating

It looks to me like you might have a tiff file instead of a geotiff?
Or they otherwise mucked with the geotiff tags and have
changed/deleted some?


> In xastir I now have a white box where the map should be, with the NW and NE
> corners where they should be.  The bottom part of the map goes right off the
> screen though.  In the white box, on the right side, are a few vertical gray
> & black lines.  I assume this means that xastir was not able to correctly
> display the file, or is this still a problem with my fgd?

You can either run some of the utilities to dump the tags and see
what these files of your really contain, comparing them to an
official unmodified USGS DRG to see the differences, or you can
use the image as-is using the ImageMagick library, just creating a
.geo file to georeference the image.

--
Curt, WE7U			    archer at eskimo dot com
Arlington, WA, USA		http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"