[OSRS-PROJ] Error when forward projection with a polar stereo graphic projecti on.. Please help.

[Ray Bryan E 2Lt 314 OSS/OSW]

Frank,

Thanks for your help.  Everything seems to work now.  As for the false
easting and northing numbers...  I was just using these as a test to input.

Let me see if I'm straight on this.  False easting and northing is nothing
more than an adjustment on the x,y plain?  So, if I'm going to make
adjustments to fit screen x,y I will use this method?

Sorry for all of the questions, I'm new to GIS/Projection type stuff.  I
have a steep learning curve.  I'm trying to draw a Polar Stereographic map
of the US by reading a map file that contains lat/lon coastal data. I'm
running input lat/lon data from the file through Proj4 and trying to get
screen x,y to draw my coastal lines etc...  I have done this with a mercator
projection and it was fairly simple.  I hope for the same by using Proj4.

Thanks for your input!
Bryan




-----Original Message-----
From: Frank Warmerdam [mailto:warmerdam at pobox.com]
Sent: Friday, December 06, 2002 10:02 AM
To: osrs-proj at remotesensing.org
Subject: Re: [OSRS-PROJ] Error when forward projection with a polar
stereographic projecti on.. Please help.


Ray Bryan E 2Lt 314 OSS/OSW wrote:
> I have tried a forward projection with a stereographic projection with no
luck.
> 
> Are there any suggestions?
> 
> Here is what I entered in the command prompt.
> 
> proj +proj=stere +lat_ts=30d00N +lat_0=90 +lon_0=90d00W +k_0=1 +x_0=200
+y_0=200
> 
> Here is the error I'm getting...
> 
> projection initialization failure
> cause: major axis or radius = 0 or not given
> program abnormally terminated
> 
> Here is what I found on the remotesensing.org website for a stereographic
projection.
>  +proj=stere +lat_ts=/Latitude at natural origin/ 
>               +lat_0=90
>               +lon_0=/Longitude at natural origin/
> 	      +k_0=/Scale factor at natural origin/ (normally 1.0)
>               +x_0=/False Easting/
>               +y_0=/False Northing/
> 
> I'm trying to do a forward projection with a polar stereographic
projection.

Bryan,

You also need an ellipse definition.  This requirement is "assumed" in much
of the documentation.

Try:
proj +proj=stere +lat_ts=30d00N +lat_0=90 +lon_0=90d00W +k_0=1 +x_0=200
+y_0=200 +ellps=WGS84

By the way, those are pretty odd x_0 and y_0 values.  Is the value
easting and northing really 200 meters?

Best regards,

-- 
---------------------------------------+------------------------------------
--
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


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