Putting my metadata where my mouth is [Re: [Xastir] Re: Bounding boxes]

[Tom Russo]

On Tue, Oct 14, 2003 at 10:04:14AM -0600, a Mr. Richard Feyler of Fort Lee, New Jersey <russo at bogoflux.losalamos.nm.us> writes 'Dear Rosanne Rosannadanna':
> On Tue, Oct 14, 2003 at 07:59:40AM -0500, a Mr. Richard Feyler of Fort Lee, New Jersey <gerry.creager at tamu.edu> writes 'Dear Rosanne Rosannadanna':
> > If it doesn't have metadata, even if you can find what might pass as 
> > sufficient information, it remains nothing more than an otherwise 
> > undocumented picture.
> 
> I agree.  The web site that distributed those geotiff files did have a 
> complete exposition of the metadata, but as a separate human-readable PDF,
> not in the geotiff metadata keys, even while saying they were georeferenced
> images.  That's a  pretty big goof IMNSHO, but could be corrected with a 
> little work.  Just have to know the arcana of geotiff keys and geotifcp's 
> metadata file format well enough to encode the projection parameters in the 
> PDF back into the geotiff files.  There weren't that many to deal with (IIRC, 
> the units (us-survey feet), the projection (2-standard parallel version of 
> lambert conformal conic), the relevent parallels and meridian, and the false 
> easting and northing, plus the relevant codes to specify that it was a 
> user-defined projection rather than one of the standard numbered PCS's).

And since I said it was so easy, I actually tried it and took the b40.tif
file Tyler originally pointed me at, which produced this from listgeo:

Geotiff_Information:
   Version: 1
   Key_Revision: 1.0
   Tagged_Information:
      ModelTiepointTag (2,3):
         0                0                0                
         5205005.7        4299352.26       0                
      ModelPixelScaleTag (1,3):
         6.6667           6.6667           0                
      End_Of_Tags.
   Keyed_Information:
      End_Of_Keys.
   End_Of_Geotiff.


Corner Coordinates:
Upper Left    (5205005.699,4299352.261)
Lower Left    (5205005.699,4253418.698)
Upper Right   (5241025.879,4299352.261)
Lower Right   (5241025.879,4253418.698)
Center        (5223015.789,4276385.479)

I then created a file (b40.metadata) that added to it, like so:
Geotiff_Information:
   Version: 1
   Key_Revision: 1.0
   Tagged_Information:
      ModelTiepointTag (2,3):
         0                0                0                
         5205005.7        4299352.26       0                
      ModelPixelScaleTag (1,3):
         6.6667           6.6667           0                
      End_Of_Tags.
   Keyed_Information:
            GTModelTypeGeoKey  (Short, 1): ModelTypeProjected
            GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
            GeographicTypeGeoKey (Short,1): GCS_NAD83
            ProjectedCSTypeGeoKey (Short,1): User-Defined
            ProjectionGeoKey (Short,1): User-Defined
            ProjLinearUnitsGeoKey (Short,1): Linear_Foot_US_Survey
            ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
            ProjStdParallel1GeoKey (Double,1): 38.6667
            ProjStdParallel2GeoKey (Double,1): 37.0833
            ProjFalseOriginLatGeoKey (Double,1): 36.3333
            ProjFalseOriginLongGeoKey (Double,1): -85.75 
            ProjFalseEastingGeoKey (Double,1): 1500000.00
            ProjFalseNorthingGeoKey (Double,1): 1000000.00
      End_Of_Keys.
   End_Of_Geotiff.


Corner Coordinates:
Upper Left    (5205005.699,4299352.261)
Lower Left    (5205005.699,4253418.698)
Upper Right   (5241025.879,4299352.261)
Lower Right   (5241025.879,4253418.698)
Center        (5223015.789,4276385.479)

The only difference between this and the previous is teh stuff in the 
"Keyed_Information" block, which will not change from map to map (of the set
on the Kentucky web site in question).  I then stuffed it into an uncompressed
tiff:
   geotifcp -g b40.metadata -c none b40.tif b40_tvr.tif
and copied that to my Xastir maps directory.

When loaded in, the map appears in the right place in the US, and the few
vector maps of roads, county lines and such that I have seem to line up 
pretty well.  The map in question happens to have a UTM grid drawn in, and 
when I position my mouse cursor to grid intersections and observe the status 
line with my coord system set to UTM, the results I see are sane.

So, Tyler, if you're willing to do a one-time "listgeo/hack on output/geotifcp" 
cycle on every map (could easily be automated with a perl or even sed script), 
you've got a free source of all the Kentucky maps you could download!  Hope 
this helps,

T.

-- 
Tom Russo   KM5VY    QRPL #1592   K2#398    http://www.swcp.com/~russo/
Tijeras, NM DM64ux   SOC #236     AHTB#1    http://www.qsl.net/~km5vy/
 "The older I grow the more I distrust the familiar doctrine that age
  brings wisdom." -- H.L. Mencken