[Proj] Beginner Question: Latitude/Longitude to x, y conversion - understanding output
AdamDynamic
helloadamdynamic+proj4 at gmail.com
Mon Feb 24 04:37:32 EST 2014
Hi,
I've been scouring the internet for a couple of days now and getting
absolutely nowhere - I appreciate this is probably a simple question once
you know the answer but any help on this would be appreciated!
I have a series of latitude/longitude coordinates that i want to plot as xy
coordinates (i.e. a flat, rectangular map).
I'm using the PyProj Python library to perform the conversion, the problem
is I can't determine what the output of the function means or represents?
e.g. Converting [51.5072,0.1275] (what Google tells me is the lat/long for
London in the UK) returns [5733755.276187301, 14193.246790158479] for a
Mercator projection - my question is '5733755.276187301 of what'? I
understand that the library converts to Proj.4 notation (?) but I can't seem
to find what the units are, or how I'd map the output onto a 900x1100
rectangle?
I'm using the following conversion formula which I found here
<http://osgeo-org.1560.x6.nabble.com/Google-Mercator-Projection-td3841191.html>
+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0
+k=1.0 +units=m +no_defs
Any assistance would be great as I haven't been able to get any information
from anywhere else. Please let me know if more information would be useful.
Thanks,
Adam
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