[Xastir-Dev] problem with drg geotiff maps

[Curt Mills]

I'm putting this back on the development list so that other people
might pipe in or at least be aware of the experiments.  The
discussion is about DRG-Enhanced topo maps for Texas.


On Fri, 1 Nov 2002, Curt Mills, WE7U wrote:

> Did you try with no FGD at all?  Looking at the code, the four lines
> that Xastir extracts from the FGD file are used only to trim at the
> neat line.  If the geoTIFF needs no trimming, you shouldn't need an
> FGD file at all, and Xastir figures that out after trying/failing at
> opening the FGD.  After that, it's supposed to continue on without
> trimming.  See if that works.  I'll try that later today too if I
> have time.

Just tried it.  The stupid things tilt, but other than that they are
displayed roughly ok.  They don't quite fit within the borders of
the 24k overlay shapefile, which showed me the tilt quickly.

So, it looks like FGD's are recommended for DRG-E's as well.  With
the FGD's I sent you, the map pixels overflow the 24k boundaries on
all sides by about equal amounts, which makes me think that either
the scaling is slightly off, or there are extra pixels attached to
all sides which aren't accounted for in the FGD or in the geoTIFF
tags.

The FGD files that I am using are modified from the downloaded ones
only by the addition of a '-' sign in front of the two boundary
longitudes.

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
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