Hi Birgit,

I can confirm your results on

POSTGIS="1.3.1" GEOS="2.2.3-CAPI-1.1.1" PROJ="Rel. 4.4.9, 29 Oct 2004" USE_STATS

0.001953125 or 0 for the given examples.

I can only guess that it is some sort of silent change in between 1.4.0 and 1.4.1. Could that be? Do have the possibility to upgrade your Postgis installation? BTW which version of Postgresql are you using?

The confirmed error is on "PostgreSQL 8.2.4 on x86_64-pc-linux-gnu, compiled by GCC cc (GCC) 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)", the correct results are obtained from "PostgreSQL 8.4.2 on i486-pc-linux-gnu, compiled by GCC gcc-4.4.real (Ubuntu 4.4.1-4ubuntu8) 4.4.1, 32-bit" (selected using "SELECT version();")

Regards,
Marc


Birgit Laggner wrote:
Hi Marc,

your results look wonderful, but I don't know how you achieve them. Here
my results for your pgsql statement and the postgis_fullversion for the
3 servers I tested the statement on:

"POSTGIS="1.4.0" GEOS="3.2.0-CAPI-1.6.0" PROJ="Rel. 4.6.1, 21 August
2008" USE_STATS"
0.001953125
0.001953125
0.001953125
0.001953125
0
0.001953125
0
0.001953125
0.001953125
0.001953125


"POSTGIS="1.3.6" GEOS="3.1.1-CAPI-1.6.0" PROJ="Rel. 4.6.1, 21 August
2008" USE_STATS"
0
0.001953125
0.001953125
0.001953125
0.001953125
0.001953125
0.001953125
0.001953125
0
0.001953125



"POSTGIS="1.3.6" GEOS="3.1.1-CAPI-1.6.0" PROJ="Rel. 4.7.1, 23 September
2009" USE_STATS (procs from 1.3.3 need upgrade)"
0
0.001953125
0.001953125
0.001953125
0.001953125
0.001953125
0.001953125
0.001953125
0
0.001953125


Any suggestions why my results are so different from yours?

Thanks and regards,

Birgit.




On 15.04.2010 11:17, Marc Jansen wrote:
Hi Birgit,

I have different results here:

http://osgeo.pastebin.com/dhPpqH9J

Regards,
Marc



Birgit Laggner wrote:
Yes, sure... Here some of my geometries with st_area=0.001953125
(1/2^9):

"SRID=31467;POLYGON((3508395.5093 5910738.8973,3508505.2864
5910690.8533,3508300.641 5910780.4164,3508395.5093 5910738.8973))"
"SRID=31467;POLYGON((3508395.5093 5949092.7294,3508333.8642
5949090.138,3508411.1808 5949093.3882,3508395.5093 5949092.7294))"
"SRID=31467;POLYGON((3498246.2563 5815493.2389,3498246.2472
5815493.1259,3498246.2094 5815493.1202,3498246.2563 5815493.2389))"
"SRID=31467;POLYGON((3539635.9601 5832797.6616,3539635.9574
5832797.6613,3539635.9565 5832797.6851,3539635.9601 5832797.6616))"
"SRID=31467;POLYGON((3546842.9496103 5778962.75289926,3546842.9761781
5778962.61321963,3546842.976 5778962.613,3546842.9496103
5778962.75289926))"
"SRID=31467;POLYGON((3427425.5879 5841806.726,3427416.0171
5841792.2466,3427416.01703247 5841792.24664866,3427425.5879
5841806.726))"
"SRID=31467;POLYGON((3538420.34038636 5912791.09822265,3538420.31141462
5912790.97224757,3538420.3113 5912790.9723,3538420.34038636
5912791.09822265))"
"SRID=31467;POLYGON((3577970.8916 5729534.987,3577827.5551
5729621.0532,3577805.6282 5729634.2192,3577970.8916 5729534.987))"
"SRID=31467;POLYGON((3472882.79775403 5870816.50310222,3472882.7978
5870816.5031,3472875.19541818 5870717.64922727,3472882.79775403
5870816.50310222))"
"SRID=31467;POLYGON((3557563.34513562 5791040.4530635,3557563.44511383
5791040.49625184,3557563.3452 5791040.4529,3557563.34513562
5791040.4530635))"

st_area=0.00390625 (1/2^8):

"SRID=31467;POLYGON((3570365.59720136 5742710.02924098,3570358.1909
5742719.6418,3570358.191599 5742719.64149272,3570365.59720136
5742710.02924098))"
"SRID=31467;POLYGON((3561579.38938441 5905129.43679735,3561545.6658
5905163.3222,3561522.09118149 5905187.00889311,3561545.6653
5905163.3228,3561579.38938441 5905129.43679735))"
"SRID=31467;POLYGON((3552150.9548 5742650.4051,3552168.62992722
5742646.68243639,3552168.6301 5742646.6818,3552150.9548 5742650.4051))"
"SRID=31467;POLYGON((3561749.8571 5865749.873,3561799.5277
5865766.3108,3561799.52805235 5865766.31075114,3561749.8571
5865749.873))"
"SRID=31467;POLYGON((3473864.032 5873365.3502,3473872.3622
5873371.4589,3473879.97516418 5873377.10501052,3473872.3622
5873371.4584,3473864.032 5873365.3502))"
"SRID=31467;POLYGON((3560788.59448517 5748665.31989661,3560796.5561
5748667.1403,3560807.5257 5748669.0521,3560796.5561
5748667.1398,3560788.59448517 5748665.31989661))"
"SRID=31467;POLYGON((3456586.93009402 5872050.7320991,3456603.71148126
5872024.70635152,3456586.9299 5872050.7319,3456586.93009402
5872050.7320991))"
"SRID=31467;POLYGON((3573125.32168799 5906771.92751555,3573125.3215
5906771.9274,3573112.75787677 5906796.71385397,3573112.7581
5906796.7139,3573125.32168799 5906771.92751555))"
"SRID=31467;POLYGON((3575905.7401 5719920.9669,3575904.88200387
5719873.25691506,3575904.882 5719873.2572,3575905.7401 5719920.9669))"
"SRID=31467;POLYGON((3547343.0802 5741914.6939,3547341.3108
5741921.4379,3547339.1261 5741930.6872,3547336.9408
5741937.6228,3547335.58835 5741941.09235,3547336.9408
5741937.6233,3547339.1261 5741930.6877,3547341.3108
5741921.4384,3547343.0802 5741914.6939))"

st_area=0.0078125 (1/2^7):

"SRID=31467;POLYGON((3650622.49435981 5875166.19247976,3650619.8317
5875115.4098,3650622.4941 5875166.1925,3650622.49435981
5875166.19247976))"
"SRID=31467;POLYGON((3568389.67127267 5851488.1421237,3568389.6712
5851488.1422,3568495.5728 5851570.3678,3568389.67127267
5851488.1421237))"
"SRID=31467;POLYGON((3571954.51978888 5753275.44491658,3571927.0019
5753378.6038,3571954.5199 5753275.445,3571954.51978888
5753275.44491658))"
"SRID=31467;POLYGON((3555658.1082 5728053.622,3555651.679
5728050.4778,3555644.8351 5728048.1717,3555634.0498
5728047.1242,3555644.8351 5728048.1723,3555651.679
5728050.4783,3555658.1082 5728053.622))"
"SRID=31467;POLYGON((3555058.35805504 5715181.02070526,3555108.2704
5715190.4028,3555058.3581 5715181.0204,3555058.35805504
5715181.02070526))"
"SRID=31467;POLYGON((3395315.40197822 5840656.87971937,3395229.2098
5840619.9673,3395315.4019 5840656.8799,3395315.40197822
5840656.87971937))"
"SRID=31467;POLYGON((3573074.18310709 5740403.73582028,3573074.183
5740403.7363,3573096.5482 5740407.9711,3573074.18310709
5740403.73582028))"
"SRID=31467;POLYGON((3544884.936 5844897.712,3544851.31613268
5844807.24085704,3544851.316 5844807.241,3544884.936 5844897.712))"
"SRID=31467;POLYGON((3576480.5538 5704180.1479,3576466.1052
5704170.6652,3576450.375 5704162.5361,3576466.1052
5704170.6657,3576480.5538 5704180.1479))"
"SRID=31467;POLYGON((3576450.375 5704162.5361,3576437.7542
5704156.0998,3576421.8422 5704149.326,3576437.7542
5704156.1003,3576450.375 5704162.5361))"

Just a few examples... As I said, all of my areas are multiples of
1/2^9...

Regards,

Birgit.



On 13.04.2010 02:08, Greg Williamson wrote:
What SRID(s) ? Could you give an example, perhaps ?

Greg W.



----- Original Message ----
From: Birgit Laggner <[email protected]>
To: PostGIS Users Discussion <[email protected]>
Sent: Mon, April 12, 2010 5:43:24 AM
Subject: [postgis-users] st_area and 0.001953125

Dear list,

when I use st_area(), I always get multiples of 0.001953125 (1/2^9)
as a
result. Can anybody explain why?

Thanks and regards,

Birgit.

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