No subject

whatever map projection you use to "proj=latlong"...

I think that would work for the most part, but it might be off if your map
projection is different from the projection your data was using and you
don't have the proper projection set in your layer definition... but since
you don't know anything about the projection your data is using, I don't
think this can be helped.

If you are using data downloaded off the internet check the site for
metadata about the shapefile.   There is a pretty good chance that the data
is unprojected, just in "latlong".   It seems like nearly everything I've
found on the net is just "latlong".

-Jeff

----- Original Message -----
From: "Giridhar Manepalli" <gmanepal at GMAIL.COM>
To: <MAPSERVER-USERS at LISTS.UMN.EDU>
Sent: Tuesday, April 19, 2005 8:17 PM
Subject: [UMN_MAPSERVER-USERS] Inverse Projection


Hello All,
When the user clicks on the map image, I calculated the
Latitude/Longitude using javascript. This pretty much assumes linear
transformation of image points to lat/long which obviously will be
erroneous. The deviation from the actual lat/long will depend on the
"projection" i have used for my shapefile.

Currently, I dont have any information of the projection system used.

Is it possible to identify more accurately the lat/long of the mouse
click without knowing the projection system?

If I know the projection system used, is it right to say that I can
accurately calculate the lat/long of the mouse click? If so, how?

I appreciate if anyone can throw some light on these issues!

Thanks
Giridhar