[postgis-users] Adding a custom projection

[Nicolas Ribot]

> Good day all
>
> My country has the following coordinate system MOLDREF 99:
> # MOLDREF 99
> <100099> +proj=tmerc +lat_0=0 +lon_0=28g24m +k=0.99994 +x_0=200000
> +y_0=-5000000 ellps=GRS80 +units=m +no_defs
>
> This is proj4 definition, now I need to add this projection to Postgis and I
> don't understand some parameters like:
>
> AUTHORITY - ?

Hi Pavel,

As postgis uses Proj4 to perform transformation operations, the useful
entries in spatial_ref_sys table is SRID and proj4text.

Authority is supposed to be the name of the Reference authority that
delivered/defined the projection (that could be the name of the
official geographic institute in your country, for instance). It is
used for informational purpose only.

>
> UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]] - ?
> PARAMETER["scale_factor",0.9999] - this is "k" i guess , correct ?

Yes

> PRIMEM - I know what datum and projections are, what does PRIMEM stands for
> ?

It stands for Prime Meridian, (Greenwich, Paris, ...) The reference
for longitude origin.

Nicolas