As I tell my students the precision is purely spurious. Geometry is stored as double precision values as far as I know but after the first few decimal places you soon get beyond what is measurable by modern survey instruments so I wouldn't worry about it.
If you take a UTM zone measurement in metres at 4240000.5555555, the values after the decimal point are decimetre, centimetre, millimetre, micrometre, nanonmetre, picometre. A picometre is 1×10−12 m - you need about 100 or more to measure an atom. Obviously with Lat/Lon you are using an angular measurement but the same concept applies. Hope this helps Phil ________________________________ From: dornakal <[email protected]> To: [email protected] Sent: Wed, 20 July, 2011 18:32:25 Subject: Re: [postgis-users] Please post - Bounding box Thank you much for quick reply. upto what precision should we store the data? Phil James wrote: > > INSERT INTO tablename (col1, col2, the_geom) > VALUES (value1, value2, geomfromtext('POLYGON((lat lon, lat lon, lat lon, > lat > lon, lat lon))',4326)) > > Where col1, col2 are column names and the geometry column is called > the_geom > > Phil > > > > ________________________________ > From: jiggi jug <[email protected]> > To: [email protected] > Sent: Wed, 20 July, 2011 14:57:00 > Subject: [postgis-users] Please post - Bounding box > > Hi, > > I have just started using postGIS. I have to populate some satellite data > into a table. I receive foot print in xml. I am getting > footprint_lat[1] = 1.98146079413183642E+01 > footprint_lon[1] =-1.55761586451820648E+02 > footprint_lat[0] =1.97588878664455372E+01 > footprint_lon[0] =-1.55439677185788781E+02 > footprint_lat[2] =1.92503820033957886E+01 > footprint_lon[2] =-1.55513901957042549E+02 > footprint_lat[3] =1.93098870612302420E+01 > footprint_lon[3] =-1.55855972208092851E+02 > > > I have to create a table with column to store the above foot print data as > polygon and insert this data into that column.Can anyone please help me > with > these create and insert statements. > > Also upto what precision should the floating point must be stored > ususally. > > Appreciate your help. > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > > -- View this message in context: http://old.nabble.com/Please-post---Bounding-box-tp32099353p32101350.html Sent from the PostGIS - User mailing list archive at Nabble.com. _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
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