[Proj] Conferting from WGS84 latlong to Transverse Mercator

Hanlie Pretorius hanlie.pretorius at gmail.com
Wed Sep 1 01:43:23 EST 2010


I'm just a bit confused about the signs of my converted coordinates.

My latlong coordinates are in South Africa: 28.375E and 27.375S

I'm using pyproj to convert from latlong to a Transverse Meractor PCS
centred on 29 deg East:

import pyproj

pr_tm = pyproj.Proj('+proj=tmerc +lat_0=0 +lon_0=29 +k=1 +x_0=0 +y_0=0
+ellps=WGS84 +units=m +no_defs')

x_latlong = 28.375
y_latlong = -27.375

x_tm, y_tm = pr_tm(x_latlong, y_latlong)

print x_tm,y_tm

-61827.9202408 -3029337.78594

My question is this: why is the x-coordinate in the TM PCS negative?
It is in the eastern hemisphere, so surely it should be positive? Or
am I missing something?


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