[Mapserver-users] Projection Help

[Paul VanDyke]

I'm sorry for not being too specific, but I didn't know what information
was necessary.  Thank you for the questions.

Here's what I'm doing:

I acquired a .jpg satellite picture of Alaska that was 5202x4002 pixels.
I cropped it to 1800x1162 pixels (to include only the relevant parts)
and saved it as a 24-bit uncompress RGB .tif file

When I add it to ArcMap, it prompts me to build pyramids, which I say
YES to and then I get a message that says, "One or more layers is
missing spacial reference information. Data from those layers cannot be
projected."

The raster shows up a just a spec on the map, but thru the
georeferencing process, I expand it to the proper proportions and then
output a recitfied image.  I realize that this image is going to be very
grainy when zoomed in, but it's just a birds eye view (a very high
bird/satellite) of our island.

The rectified .tif does not have a coordinate system defined for it yet
as checked with the LISTGEO command.

Then I assign it a projection from within ArcCatalog by right-clicking
and selecting properties; choosing the "Spacial Reference" tab and
clicking Edit; I then choose Import and select one of the shape files
that is on the map and import it's coordinate sytem, which happens to be
NAD_1927_StatePlane_Alaska_5_FIPS_5005.

When I look at my MapServer output, the raster is plotted south of the
shapefile by a big stretch. I originally said 100 miles but I think it's
probably more like 700 miles.  Changing the projection in my .map file
from init=epsg:26705 to init=epsg:26735 make the map disappear entirely.
One of the rasters that work is of type 26705, but the shapefile that
I'm working with is 26735.

Please feel free to comment on my proceedures.  Maybe I'm missing a
step, but it all looks good in ArcMap...

Thanks,

Paul


-----Original Message-----
From: Frank Warmerdam [mailto:warmerdam at pobox.com] 
Sent: Wednesday, April 07, 2004 9:29 AM
To: Paul VanDyke
Cc: mapserver-users at lists.gis.umn.edu
Subject: Re: [Mapserver-users] Projection Help


Paul VanDyke wrote:
> Most of my raster images are working great and I am very thankful to 
> those who helped me.  However, I am having problems with a few of my 
> rasters and I'm scratching my head...
> 
> I am adding them as a layer to my ArcMap project, doing the 
> georeferencing, then exporting them out.  I've gotten a few to work, 
> but others haven't.  The last one I did showed up on my MapServer map 
> about 100 miles south of where it should have been.  I've tried 
> playing with the projection in my .map file and I've tried defining 
> the spacial information in ArcCatalog.  I realize that I don't have 
> the knowledge/background/training to do the job that I'm doing, and so

> I am asking for help from this community.  If you can provide me with 
> any links/websites with further information, I'd be very appreciative.

> If you can tell me why my raster displays 100 miles south (roughly) of

> where it's supposed to, I'd be indebted.
> 
> The map in question is Map 9 at http://209.165.152.73 and you'll have 
> to zoom out to the south to see what I'm talking about.

Paul,

This isn't much for us to go on.

Where did you get the data?  Did it come with any coordinate system
information or other metadata that might be helpful?  Can you go back to
the source to get such information?  Does it display properly in ArcMap?
What projection definition are you using now?  Why?  Do you have other
layers that are working properly?  What coordinate system are you using
for them?

A 100 mile error could be the result of a number of things.  Perhaps you
are using the wrong state plane zone, or are missing false
easting/northings. What it is not is a datum/ellipsoid error since those
errors would be tiny by comparison.

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    | Geospatial Programmer for Rent