[postgis-users] st_area and 0.001953125

Thu Apr 15 04:37:01 PDT 2010

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 <birgit.laggner at vti.bund.de>
>>>> To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
>>>> 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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>>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>>>
>>>>
>>>>
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>>>>         
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>>>   
>>>       
>>     
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-- 

  Dipl.-Geogr. Marc Jansen
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