I have a set of city networks whose coordinates are specified in lat/lons. I wish to run an algorithm on each network that treats them as a planar graph. I'm using python and can use pyproj to project the network appropriately, the problem is that I don't know the appropriate CRS for each city, e.g., for my test case, Harare, I define the variable: zimbabwe_reference='epsg:20935'.
What I'd like to do is call a function like crs=getCRS(lat, lon) and get the relevant string to pass on to pyproj.
Answer
You can calculate the UTM zone of each town center from the longitude, starting at zone 1 from -180°E to -174°E. zone=ROUND((183+longitude)/6;0) should calculate that in one step.
The EPSG code is 32600+zone for positive latitudes and 32700+zone for negatives.
Together in one formula:
EPSG=32700-ROUND((45+latitude)/90;0)*100+ROUND((183+longitude)/6;0)
Alternatively, create a custom CRS on the town center:
+proj=tmerc +lat_0=(latitude) +lon_0=(longitude) +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
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