[Proj] Getting Extent Using Custom Projection

Gerald I. Evenden geraldi.evenden at gmail.com
Tue Jul 10 23:44:46 EDT 2007

On Tuesday 10 July 2007 11:10 pm, Bradley Mclain wrote:
> Ok what I have done is made a custom projection and I want to get the new
> extent for my data.
> The original projection:
> "# GDA94 / MGA zone 55
> <28355> +proj=utm +zone=55 +south +ellps=GRS80 +towgs84=0,0,0,0,0,0,0
> +units=m +no_defs  <>"
> The custom projection:
> <41002> +proj=merc +lat_ts=0 +lon_0=0 +k=1.0 +x_0=0 +y_0=0 +a= 6378137.0
> +b= 6378137.0 +units=m <>
> I understand that this must be done by console commands or something but I
> have no idea how.
> Brad

If you are using proj or lproj just execute the command:

proj +proj=merc +a= 6378137.0 +b= 6378137.0


lproj +proj=merc +a= 6378137.0 +b= 6378137.0

I edited out all the superfluous material.  Then follow the above commands 
with longitude latitude pairs and Cartesian will be output.

More appropriately create a file of your geographic coordinates in file 
geog_data.txt and do:

proj +proj=merc +a= 6378137.0 +b= 6378137.0 <geog_data.txt >results.txt

The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939)  British psychologist

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