[Mapserver-users] Re: ogr broken perhaps? Problems with on-the-fly and other projections.

Andrew selkiesdad at twcny.rr.com
Fri May 28 07:52:52 EDT 2004

One more try :

I know there is an answer to this, and I am certain it has been 
encountered before unless it is simply a subtle problem with my compile 
of ogr.

The ogr2ogr utility and, I assume, the mapserve cgi, project my state 
plane either incorrectly or with some transformation of the origin. I 
don't know how this might be characterized but the shifted coordinates 
are as reported (and quoted below). The associated eastings are :UTM 
500000m, STP 150000 feet. I assume the problem is related to the use of 
decimal degrees in the UTM file and the false eastings and northings of 
both files or the fact that the transformed STP file reports units as 
meters and not feet, but I don't know how to test this. The original 
shape files for the STP projection should be in feet, but the world file 
and embedded georeferenceing info in the tifff don't list the projection 
type name or northings/eastings, though they are included in the 
PROJECTION section of the mapfile. I could try to use the proj.4 
commands to project the locations in each dbf file and then use the 
results as a replacement shapefile, but I prefer to learn why the 
on-the-fly and manual transforms differ from the expected region. Any 
help would be appreciated, since my project requires these datasets and 
the use of (to-be-projected) lat/lon locations from other research.

quote from previous post:

The coordinate shifts in the projected shape file after using ogr2ogr 
compared to the correct region settings are:

original lon/lat (-75.860047, 44.050400) - (-74.525683, 45.015850) ---> 
( add this: decimal degrees in a meter-referenced UTM projection)
converted state plane (-406072.543743, -4299527.573525) - 
(-406071.208006, -4229526.607082) ---> (add this: reports as meters in 
what should be foot units)
Ref map base state plane (312000.0, 2092000.0) - (390000.0, 2168000.0) 
---> (add this: reports no units, assumed feet due to documentation for 
STP NY east zone.)

lat lon comes from a UTM Zone 18N NAD83 GRS80 system (epsg:26918)
state plane is NY East zone (epsg:32115)

More information about the mapserver-users mailing list