[postgis-users] transform problem

[ujunge at pmcentral.com]

hi,

i have following transformation problem:

    select transform(GeometryFromText('POLYGON(
        (-80 40,-75 35,-70 40.1,-80 40),(-90 40,-85 35,-80 40,-90 40)
    ',4326),102013)

does NOT work, while

    select transform(GeometryFromText('POLYGON(
        (-80 40,-75 35,-70 40.01,-80 40),(-90 40,-85 35,-80 40,-90 40)
    ',4326),102013)

does work (only the 40.1 changed to 40.01).

Also,

    select transform(GeometryFromText('POLYGON(
            (-80 40,-75 35,-70 40.1,-80 40)'
    ,4326),102013)

and

    select transform(GeometryFromText('POLYGON(
            (-80 40,-75 35,-70 40.01,-80 40)'
    ,4326),102013)

do both induvidually work.

It doesen't matter, what kind of destination coordinate system i choose, as
long it's not longlat.

That means from my understanding, it is rather a data-handling problem
within the postgis transform-function than a projection problem within
proj4.

I had a couple of multipolygons and was trying to calculate the area
(in sqmeter or sqmiles) and had to reproject the data. But in 30% of all
cases
these queries did return an error. I manually simplified the multipolygons,
removed points and decimals in order to figure out if there is a
data-problem.
But even in the extremly simplified case shown above the same error occured.


I'm using W2K and compiled postgresql-7.4.1-3 with postgis-0.8.0 in CYGWIN
after running into troubles with postgis-0.8.1:

Reading some acrticles in the mailing list and trying very hard, i was not
able to figure out a way of getting the loader to write the database-name
into the created sql-statement(s), and the -D flag produced non readable
dumps.


But i have to say that the installation intructions are very well done !



Uwe Junge
PMCentral Systems, Inc.
4201 Pinefield Court
Fairfax, Virginia 22033

Tel: +1 (703) 378-0952




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