raster vs shp files extents don't match

[Frank Warmerdam]

Paul A Malabad wrote:
> I have found out that the DIgital orthos are Virginia State Plane 
> Coordinate system.  Through the metadata on the dvd, I found that 
> although the discs read VASPCS North, The metadata actually refers to 
> the VASPCS south.  I metadata also refers to the units in US survey 
> foot.  whereas the epsg file refers to metre.  I have tried using the 
> information from the meta to create a separate projection, but it is not 
> working correctly.  Can you see anything wrong in my translation.

>   PROJECTION
>     "init=epsg:102746"
>   END

Paul,

The ESRI coordinate system number 102746 is in US feet,
but I believe that the vector coordinates are in meter
based on the scale of the values.  So I'm not sure that 102746
is right for the vectors.  I think EPSG:32146 (VA SPCS North / meter)
or EPSG:32147 (VA SPCS South / meter) would be more appropriate.

EPSG 32146 can be described with the following proj.4 string:

  +proj=lcc +lat_1=39.2 +lat_2=38.03333333333333 +lat_0=37.66666666666666
    +lon_0=-78.5 +x_0=3500000 +y_0=2000000 +ellps=GRS80 +datum=NAD83
    +units=m +no_defs

>     PROJECTION
>       "proj=latlong"
>       "ellps=GRS80"
>       "datum=NAD83"
>       "lat_0=36.333333334"
>       "lat_1=36.766666667"
>       "lat_2=37.966666667"
>       "lon_0=-78.5"
>       "units=ft"
>     END

Note that this definition is ignoring the false easting and northing
which are very important.  In my fairly recent file VA SCPS South (ftUS)
is EPSG:2284 and maps to the PROJ.4 string:

   +proj=lcc +lat_1=37.96666666666667 +lat_2=36.76666666666667
     +lat_0=36.33333333333334 +lon_0=-78.5
     +x_0=3500000 +y_0=1000000.0
     +ellps=GRS80 +datum=NAD83 +to_meter=0.3048006096012192 +no_defs

Note the important +x_0 and +y_0 values.

So I *think* you want to use EPSG:32146 for the vector layer, and
EPSG:2284 for the raster layer.  Then you can set your map level
projection to whichever you wish.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGF, http://osgeo.org