[postgis-users] Coordinate format for SRID:4326

[Ben Madin]

Michael,

On a computer, use decimal degrees. x axis first (abscissa - Eastings or Longitude), y axis second (ordinate - Northings or Latitude).

In the cockpit, you may find yourself using sexagesimal degrees, and you may hear people quote 'Lat-lon', but if you look at the def's below, you will see +proj=longlat

just my opinion...

cheers

Ben





On 11/07/2011, at 10:40 PM, Gheorghiu, Mihai wrote:

> I am confused by the references to "sexagesimal degrees" that I found on this list and elsewhere on the Web.
> SRID:4326 used for geography representation in postgis is based on EPSG:4326 (http://spatialreference.org/ref/epsg/4326/postgis/):
> INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 94326, 'epsg', 4326, '+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs ', 'GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]]');
> If I query Oracle 10g
> SELECT * FROM MDSYS.SDO_CS_SRS WHERE SRID='4326';
> WGS 84                4326       4326       EPSG. See 3D CRS for original information source.             GEOGCS [ "WGS 84", DATUM ["World Geodetic System 1984 (EPSG ID 6326)", SPHEROID ["WGS 84 (EPSG ID 7030)", 6378137, 298.257223563]], PRIMEM [ "Greenwich", 0.000000 ], UNIT ["Decimal Degree", 0.01745329251994328]]
> My understanding of "decimal degrees" is that 72 degrees 30 minutes are represented as 72.5, and that's the way I used to input coordinates in Oracle.
> Now if I want to input the same value in postgis, do I have to use a format such as 72d30m00s00 ("sexagesimal degrees"), or 72.5 ("decimal degrees")?
> To add to the confusion, in postgis there is SRID:900914, which is the exact replica of Oracle's 8307, and both use the term "decimal degrees".
>  
> Thank you very much for your support.
>  
> Michael
> 
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