[geos-devel] distance

[Frank Warmerdam]

Tomas,

If you dig into one of the representations, such as "well known text as HTML"
you can see the units.  In the WKT it is:

PROJCS["POSGAR 94 / Argentina 6",
    GEOGCS["POSGAR 94",
        DATUM["Posiciones_Geodesicas_Argentinas_1994",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6694"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.01745329251994328,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4694"]],
    UNIT["metre",1,   <<<<<<<< ***************** UNITS *****************
        AUTHORITY["EPSG","9001"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",-90],
    PARAMETER["central_meridian",-57],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",6500000],
    PARAMETER["false_northing",0],
    AUTHORITY["EPSG","22186"],
    AXIS["Y",EAST],
    AXIS["X",NORTH]]


On Fri, Aug 26, 2011 at 11:42 AM, Tomas Neme <lacrymology at gmail.com> wrote:
>> Hi Tomas,
>>
>> All the GEOS operations are done in a unitless Cartesian space.
>> Distance is unitless. For example, the distance between a point at (0,
>> 0) and (1, 1) is sqrt(2). 22186 has units of meters, right? As long as
>> your distances are in meters (1000 in your case), you'll be fine.
>
> I thought so, but.. how do I know this?
>
> http://www.spatialreference.org/ref/epsg/22186/
>
> this is all the info I could get on 22186, it doesn't say anything
> about units. we use meters in AR, so I guess you must be right, but
> not the point.. finding info on this subject is very hard =/
>
>
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