Display a map using Tiger data

[Frank Warmerdam]

On 4/19/05, ryan <ryant at cs.utah.edu> wrote:
> Hi,
> 
> I'm having trouble displaying a map of street data i got from the tiger LINE
> project.  mapserv doesn't give me any errors, just shows a blank png.  I can
> run the demo stuff fine.  I've also tried changing STATUS from ON to OFF to
> DEFAULT in my mapfile.  Also, I don't know for sure what the extent of my
> map should be, but i'm passing 1.00, 1.00, 50000.00, 50000.00 because i can
> use arcexplorer on my windows machine to find that the dimensions of the map
> are about 50Km by 50Km.

Ryan, 

I would suggest the issue is extents related. Likely all your vectors are
getting drawn in one pixel.  I would suggest you use some utility to get
the extents of your dataset in their intrinsic coordinate system which would
be lat/long if they are tiger/line data (that hasn't been reprojected).  

For shapefiles and a few other formats, you could use ogrinfo. 

eg. 
 ogrinfo -ro -so -al abc.shp 

> Here is the web address i access:
> http://localhost/cgi-bin/mapserv?map=/usr/bin/apache/htdocs/mapserver/simple.map&mode=map&layer=Freeways&mapext=1.00%201.00%2050000.00%2050000.00&imgsize=300%20300
> 
> And my map file is here:
> 
> #-------start of map file---------------#
> NAME sampleMapServer
> # the below extents and size are provided in the URL and so must be removed
> #EXTENT 482925.85 3625874.39 497393.16 3617143.43

Note, just because you are listing the extents in the url doesn't
mean you have to remove them from the map.  The info passed in
the url just overrides the info in the map file.  I generally try to fill 
out reasonable information in the mapfile so I can use utilities like
shp2img for debugging purposes. 

PS. there are lots of possible reasons your map could be failing to draw
besides the extents issue, but it is pretty hard for us to remotely debug
without all supporting files, and a clear understanding of what version
of mapserver you are running.  Generally "mapserv -v" output is more
useful than your configure line. 

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent