[mapserver-users] Nationalatlas Shapefile Projection

[Sathiskumar Govindasamy]

Hi all,

To give a better idea about what I am trying to acheive, I have explained 
little bit more in this mail than before. I wanted the mapserver to 
generate the image of USA in the "lcc : Lambert Conformal Conic projection" 
or "aea : Albers Equal Area" or which ever suits best for US. I have the 
National Atlas US States shapefile statesp020.xxx . The following is the 
map file.

NAME USA
STATUS ON
EXTENT -126 50 -66 24
UNITS METERS
SIZE 700 550
SHAPEPATH "data"
IMAGECOLOR 79 173 253

PROJECTION
         "proj=lcc"
         "lat_0=24"
         "lat_1=50"
         "lon_0=-99"
END

WEB
         TEMPLATE demo.html
         LOG demo.log
END

#
# Start of symbol definitions (we're only using a few)
#
SYMBOL
         NAME 'circle'
         TYPE ELLIPSE
         POINTS 1 1 END
         FILLED TRUE
END

#
# Start of layer definitions
#
LAYER
         NAME statesp020
         MAXSCALE 600000
         TYPE POLYGON
         STATUS DEFAULT
         DATA statesp020
         PROJECTION
                 "proj=latlong"
                 "ellps=clrk66"
         END

         CLASSITEM 'state'
         CLASS
                 NAME 'Unwanted States'
                 EXPRESSION /'Virgin Island'|Puerto|Alaska/
                 OUTLINECOLOR 198 243 255
                 COLOR 198 243 255
         END
         CLASS
                 NAME 'State & Nation Boundary'
                 EXPRESSION /./
                 OUTLINECOLOR 180 180 180
                 COLOR 255 255 255
                 OVERLAYSYMBOL 'circle'
                 OVERLAYSIZE 2
                 OVERLAYOUTLINECOLOR 180 180 180
         END

         TOLERANCE 0
END

END

In the Map PROJECTION Section when I change the above shown on to 
proj=latlong and remove lat_0 and other stuff, then the map shows up 
correctly. But, when I have it as shown above, I just only see an image 
with solid image color. Can someone tell me where I am making mistake ?

Thanks
Sathis

Kieran J. Ames wrote:

Sathis,
I'll share the little I know with you.
You need to investigate projections in general. Different projections render
maps in different ways. If you have ArcView (what I use), you can take your
UNPROJECTED DATA (Decimal Degrees) and PROJECT it. This will allow you to see
what happens. If you can't do that, then you might post to the group and ask
them what the best projection for this would be.
eg: if you want to show North America and NOT zoom in, you may choose one
projection over another. Tell the group what you want to accomplish and go 
from
there.
HTH.
Kieran
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