[Xastir] SDTS to shapefile conversion?

[Tom Russo]

On Mon, Jan 03, 2005 at 02:13:56PM -0600, we recorded a bogon-computron collision of the <gerry.creager at tamu.edu> flavor, containing:
> Fort those of you who followed the APRS Sig thread about Tiger 
> inaccuracies a couple of weeks or months ago, this is a significant 
> deal.  I may want to snag the shapefiles; I'll get ahold of the player 
> in NYC who was so concerned about the TigerLine files.  This should make 
> him happier.
> 
> One caveat: It is my understanding from our USGS State Mapping 
> Coordinator that not all of the SDTS coverages have been appropriately 
> reprojected to NAD83.

In my experience very few have been.  Some of the SDTS vector data is 
nothing more than SDTS transfers of DLG-O data from the mid-70's and earlier.
They remain in the datum that was used when they were used for creation of
topo quads.  

For the hypsography layers the age of the data is probably not as important as 
it is for the road layers, but basically if the SDTS transfer was done off
of old DLG-O's, it remains in the old NAD27 datum.  Fortunately the SDTS
format contains projection and datum information and ogr2ogr knows what it is.

When converting to shapefile a useful .prj file is created that contains
projection and datum information that can be used for reprojection/datum shift.
In fact, since we're using ogr2ogr to do the conversion to shapefile, 
one could force the issue and do

 ogr2ogr -f "ESRI Shapefile" -t_srs EPSG:4326 output_directory inputCATD.DDF

and get lat/lon shapefiles in WGS84 directly.

> 73, gerry
> 
> Jason Winningham wrote:
> >
> >On Jan 3, 2005, at 11:49 AM, Tom Russo wrote:
> >
> >>It can, and it's easy. Assumning one has an SDTS vector layer untarred 
> >>in the
> >>current directory and gdal installed in the user's path,
> >>
> >>ogr2ogr -f "ESRI Shapefile" output_directory <layer CATD file>
> >
> >
> >thanks.  I'll try this out.
> >
> >>Note that USGS has announced that they are retiring the distribution of
> >>SDTS DLG data on 30 Jan 2005.  They apparently consider it outdated
> >>and plan to direct folks at national atlas data.  Download of DLG and 
> >>DEM data
> >>from the USGS ftp site will be disabled on 30 Jan.  If you like this 
> >>data and
> >>want to stock up, your window is closing.
> >
> >
> >I've got all the DLG data (grabbed it a few weeks ago) and can make it 
> >available.  I'll step up my search for a suitable server here.
> >
> >-Jason
> >kg4wsv
> >
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> 
> -- 
> Gerry Creager -- gerry.creager at tamu.edu
> Texas Mesonet -- AATLT, Texas A&M University	
> Cell: 979.229.5301 Office: 979.458.4020
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-- 
Tom Russo    KM5VY     SAR502  DM64ux         http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://www.qsl.net/~km5vy/
 "When life gives you lemons, find someone with a paper cut."