[Mapserver-users] Geotiff and Extent confusion

[Dylan Keon]

As an addendum to Ed's note, you can also find DRGs for Georgia at 
http://csat.gatech.edu/drg/drg.html .  I can echo Ed's comments 
regarding the variability of projections, DPI, etc.  I've run into the 
same issues when stitching together DRGs from just four states - I can 
imagine the amount of normalizing Ed had to do for his operation :-)


On 12/24/2003 03:01 PM Ed McNierney wrote:
> Michael -
> 
> I think Dylan's two suggestions are correct.  I just wanted to add that
> you need to be a bit careful using the data you have in a GIS system.
> The TopoZone Pro downloads let you retrieve the original data we get
> from the USGS, the Tennessee Valley Authority, and the State of
> California.  The primary reason we provide that feature is so TopoZone
> Pro subscribers can look at the map collar information (revision
> history, township/range labels, etc.) that gets cut off in TopoZone.
> 
> We're finding that many people are using this as a source of GIS data.
> That's OK, but the data's very messy and inconsistent - when we say we
> let you download the data as we get it, we mean exactly that <g>.
> You'll find that some of the data (from the TVA, for example) aren't
> GeoTIFFs, some is projected in NAD83 and some in NAD27, most is UTM but
> California is in an Albers projection, most are 250DPI but California is
> 400DPI and many newer DRGs are 500DPI, etc., etc.
> 
> The TIF/TFW files should work correctly for the simple example you're
> trying, but if you try to expand beyond that one file you may hit quite
> a few bumps in the road.  One of the major tasks in creating TopoZone in
> 1999 was to figure out how to normalize all this messy data!
> 
> Let us know if you have any trouble with the file after you've looked at
> Dylan's suggestions.
> 
> 	- Ed
> 
> Ed McNierney
> President and Chief Mapmaker
> TopoZone.com
> ed at topozone.com
> 
> 
> -----Original Message-----
> From: Michael Hughes [mailto:mike at probass.com] 
> Sent: Wednesday, December 24, 2003 2:57 PM
> To: Mapserver-users at lists.gis.umn.edu
> Subject: [Mapserver-users] Geotiff and Extent confusion
> 
> I hate posting this because I see the same question posted again and
> again in the list.  Unfortunately there are no real answers on the list
> or the wiki, so here it goes again.
> 
> I have installed mapserver 4.01 and verified that it works via the demo.
> I have downloaded a USGS GeoTiff file from topozone and the associated
> tfw file.  I adjusted my map file to attempt to load the tif file
> instead of the pngs created for the demo.  Of course I cannot get the
> darned thing to display.  I am sure that the problem lies in the extent
> settings.  I am just not smart enought to fix it yet.  The values
> provided by gdalinfo do not match the values provided in the tfw file
> just to add to my confusion.  I am trying to simply display the image
> with the mapping server, without adding overlays or anything else at
> this point.  I am sure that it is simply a newbie mistake that is
> keeping me from displaying the image successfully, hopefully someone can
> help me out.  I have provided all of the information that I think is
> applicable below.
> 
> Michael Hughes
> 
> 
> ./mapserv -v
> MapServer version 4.0.1 OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP SUPPORTS=PROJ
> SUPPORTS=FREETYPE SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT INPUT=TIFF
> INPUT=EPPL7 INPUT=JPEG INPUT=GDAL INPUT=SHAPEFILE
> 
> cat  o34084b1.wld
> 2.438400000000
> 0.000000000000
> 0.000000000000
> -2.438400000000
> 763785.222415230000
> 3794653.234146172600
> 
> /usr/local/bin/gdalinfo o34084b1.tif
> Driver: GTiff/GeoTIFF
> Size is 5717, 6933
> Coordinate System is `'
> Corner Coordinates:
> Upper Left  (    0.0,    0.0)
> Lower Left  (    0.0, 6933.0)
> Upper Right ( 5717.0,    0.0)
> Lower Right ( 5717.0, 6933.0)
> Center      ( 2858.5, 3466.5)
> Band 1 Block=5717x6933 Type=Byte, ColorInterp=Palette  Color Table (RGB
> with 256 entries)
>    0: 0,0,0,255
>    1: 255,255,255,255
>    2: 0,151,164,255
> <...snip...>
> 
> cat o34084b1.map
> NAME  BufordDam
> SIZE 600 600
> EXTENT 763785.22241523 3794653.23414617 777725.55521523 3777747.80694617
> SHAPEPATH "/var/www/html/maps/"
> DEBUG on
> 
> WEB
>  LOG "/tmp/buforddam.log"
>  HEADER BufordDam_header.html
>  TEMPLATE BufordDam.html
>  FOOTER BufordDam_footer.html
>  MINSCALE 1000
>  MAXSCALE 1550000
>  IMAGEPATH "/var/www/html/maps/images/"
>  IMAGEURL "/maps/images/"
> END
> 
> LAYER
>  NAME "BufordDam"
>  DATA o34084b1.tif
>  TYPE raster
>  STATUS DEFAULT
> END #END OF LAYER
> END # Map File
> 
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