[mapserver-users] Nationalatlas Shapefile Projection

[Sathiskumar Govindasamy]

Thanks guys. That was it. It works great.

-Sathis

Ed McNierney wrote:

>Sure - just use PROJ, the projection tool MapServer uses (available from
>http://www.remotesensing.org/proj).  The "four corners" technique is a
>good start, but please remember that it won't always ensure that the
>entire original area is visible in the output area.  But it's usually
>fine and you can tweak things from there.
>
>	- Ed
>
>Ed McNierney
>Chief Mapmaker
>TopoZone.com
>ed at topozone.com
>(978) 251-4242
>
>
>-----Original Message-----
>From: Stephen Woodbridge [mailto:woodbri at swoodbridge.com]
>Sent: Friday, March 22, 2002 8:22 AM
>To: Ed McNierney
>Cc: Sathiskumar Govindasamy; mapserver-users at lists.gis.umn.edu
>Subject: Re: [mapserver-users] Nationalatlas Shapefile Projection
>
>
>OK, so is there a utility that lets you say project the extents so you
>have new numbers for you map file? You would probably want to project
>all four corners of your extents and then take the exnts of the
>projected corners to be you new extents in the project space.
>
>-Steve
>
>Ed McNierney wrote:
>
>>Sathis -
>>
>>Your EXTENT numbers are in the same units your output projection is
>>
>in.
>
>>If you're displaying decimal degrees, the extents work.  When you
>>project the output to LCC, the units change completely, and the EXTENT
>>numbers now specify a tiny little area that's nowhere near the United
>>States.  That's why you get a blank image.
>>
>>    - Ed
>>Ed McNierney
>>Chief Mapmaker
>>TopoZone.com
>>
>>-----Original Message-----
>>From: Sathiskumar Govindasamy [mailto:gsathis at yahoo.com]
>>Sent: Thursday, March 21, 2002 9:26 PM
>>To: mapserver-users at lists.gis.umn.edu
>>Subject: Re: [mapserver-users] Nationalatlas Shapefile Projection
>>
>>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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