[Xastir-Dev] problem with drg geotiff maps

[Gerry Creager]

<SlapToTheHead>  The registration points for DRG[E] will not be corner 
points but will be within the image.  Otherwise you can't really 
register them right.
</SlapToTheHead>

Sounds like, if they're tilted, they're UTM.  Again, I'll check soon as 
I have some time.

gerry

Curt Mills wrote:
> 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.
>