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Re: Wrong data returned from MYSQL
Posted by: Lenz Grimmer
Date: February 19, 2008 06:35AM

Hi Eric,

eric chang Wrote:
-------------------------------------------------------
> Using the following sql on MySQL version 4.1:
> select astext(map_point) ... where
> contains(GeomFromText('Polygon((
> 39.09889382148975 -74.68677520751953,
> 39.0930319292927 -74.63802337646484,
> 39.029585766893106 -74.6685791015625,
> 39.0421195689398 -74.71389770507812,
> 39.09889382148975
> -74.68677520751953))'),map_point)
>
> query returns some data as below, which seem to be
> outside the polygon area specified (verified using
> google map api)
>
> "POINT(39.0984 -74.713491)","
> "POINT(39.098255 -74.713217)"
> "POINT(39.09849 -74.713663)",
> "POINT(39.098885 -74.712646)"
> "POINT(39.097613 -74.713776)"
> "POINT(39.098328 -74.713354)"
> "POINT(39.097665 -74.713885)"
> "POINT(39.098312 -74.713324)"
> "POINT(39.098423 -74.713534)"
> "POINT(39.098219 -74.713148)"
> "POINT(39.098238 -74.713184)"
>
> Anybody has idea what the problem might be?

I assume this is because the current GIS implementation in MySQL uses minimum bounding rectangles instead of the exact polygon boundaries.

However, work is in progress to improve these functions - it would be great if you could test this with our new GIS functions: http://forge.mysql.com/wiki/GIS_Functions

Lenz Grimmer - MySQL Community Relations Manager - http://de.sun.com/
Sun Microsystems GmbH, Sonnenallee 1, 85551 Kirchheim-Heimstetten, DE
Geschaeftsfuehrer: Thomas Schroeder, Wolfgang Engels
Vorsitz d. Aufsichtsrates: Martin Haering AG Muenchen: HRB161028

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