# [postgis-users] Please post - Bounding box

Phil James borntopedal at yahoo.co.uk
Wed Jul 20 13:00:02 PDT 2011

```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 <jiggijug at gmail.com>
To: postgis-users at postgis.refractions.net
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 <jiggijug at gmail.com>
> To: postgis-users at postgis.refractions.net
> 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
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>
>

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