[Mapserver-users] FW: [postgis-users] Postgis Transform Problem

[Benjamin Wragg]

179.99 and 89.99 work OK. The problem is that I receive on a regular
basis minx,miny,maxx,maxy coordinates which define the area of a
hardcopy map boundary. Since many hardcopy maps are made of the entire
earth, the coordinates sent are -180,-90,180,90. I then create PostGIS
features from these coordinates.

If I project the data in ArcView 8 I get something like the attached
image. The purple/pink is a box I defined as -180,-90,180,90 using WGS84
and then projected it to Mercator. I was hoping to achieve similar using
PostGIS.

What did you mean by 'exercising tmerc at the boundaries'? 'tmerc'?

Thanks,

Benjamin

(I removed the image for the list. If you need it let me know)

-----Original Message-----
From: Paul Ramsey [mailto:pramsey at refractions.net] 
Sent: Tuesday, 1 July 2003 11:57 PM
To: bwragg at tpg.com.au
Subject: Re: FW: [postgis-users] Postgis Transform Problem


cs2cs exercises proj4 which is what postgis uses, so the test is 
equivalent.
You realize that you are exercising tmerc at the boundaries, right? I 
do not know what the correct behavior should be at that coordinate. 
What happens when you try 179.99 89.99?

On Monday, June 30, 2003, at 10:53 PM, Benjamin Wragg wrote:

>
> I tried the cs2cs utility. I think I'm passing the correct paramaters.
> If I enter the following:
>
> 	cs2cs +proj=latlong +ellps=WGS84 +to +proj=merc +lon_0=150.0
> 	180 90
>
> I get
>
> 	*	* 0.00
>
> If I type any other coordinate I get a figure back. So is the cs2cs
> utility what Postgis uses to project it's coords? If it does, it seems

> this is whats causing the problem.
>
> Thanks,
>
> Benjamin
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of 
> Paul Ramsey
> Sent: Wednesday, 25 June 2003 10:55 PM
> To: bwragg at tpg.com.au; PostGIS Users Discussion
> Subject: Re: [postgis-users] Postgis Transform Problem
>
>
> Those coordinates are right on the edge of the global plane, could be
> hitting the edge of validity in the reprojection library. Try testing 
> the same stuff directly using the proj4 cs2cs utility.
>
> On Tuesday, June 24, 2003, at 10:35 PM, Benjamin Wragg wrote:
>
>> I'm having a problem with the transform function in Postgis. If I run
>> the following query:
>>
>> select transform(GeometryFromText('MULTIPOLYGON(((112 -45 ,112 -10
>> ,155 -10 ,155 -45,112 -45)))',4326),54004)
>>
>> I get:
>>
>> SRID=54004;MULTIPOLYGON(((12467782.9688466
>> -5591295.91855339,12467782.9688466 -1111475.10285223,17254521.0729574
>> -1111475.10285223,17254521.0729574 -5591295.91855339,12467782.9688466
>> -5591295.91855339)))
>>
>> But if I do:
>>
>> select transform(GeometryFromText('MULTIPOLYGON(((-180 -90 ,-180 90
>> ,180 90 ,180 -90,-180 -90)))',4326),54004)
>>
>> I get:
>>
>> Error: transform: couldn't project polygon
>> Warning: Error occurred while executing PL/pgSQL function transform
>> Warning: line 2 at return
>>
>> Any ideas why? I turned the postgresql log level to debug5 to see if
>> I
>
>> could get more detailed errors, but it's exactly the same error. I'm
>> running postgresql 7.3.2, postgis 0.7.5 and proj 4.4.7
>>
>> Thanks,
>>
>> Benjamin Wragg
>>
>>
>       Paul Ramsey
>       Refractions Research
>       Email: pramsey at refractions.net
>       Phone: (250) 885-0632
>
>
> _______________________________________________
> postgis-users mailing list postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>
>
      Paul Ramsey
      Refractions Research
      Email: pramsey at refractions.net
      Phone: (250) 885-0632