[postgis-users] GPS systems and projections

[James Dominy]

Hi all,

I have some GIS data in "GCS_WGS_1984". It's currently stored in shape files.
I've successfully imported it into postgis using SRID = -1 (because I can't find
GCS_WGS_1984 in SPATIAL_REF_SYS). I can generate an SVG file containing features
matching a query and it looks okay. But, what I would like to be able to do is
float the mouse over the image in a web browser and have it report the GPS
co-ordinates of the mouse cursor. I figure this means I need to re-project the
image in the relevant GPS co-ordinate system, which as far as I can tell means I
actually have to store the features with a valid SRID (i.e. not -1)... So I
guess this boils down to

a) What is the SRID for GCS_WGS_1984, and if there isn't one, how do I go about
creating one from the info in the .prj of a shape file?

b) More generally, if I have a shape file with a .prj not listed in
SPATIAL_REF_SYS, how do I go about importing it into postgis such that I can
re project it later?

b) In what SRID should I project the SVG, such that I can calculate GPS
coordinates of the mouse cursor in a user selectable GPS system, preferably
without reproducing the entire SVG in a different projection?

Thanks,
James