[Proj] How to Scale a Mercator projection?

Gerald I. Evenden gerald.evenden at verizon.net
Tue Jul 25 20:25:39 EDT 2006

On Tuesday 25 July 2006 5:58 pm, Christopher Barker wrote:
> ValueError: Failed to initialize PROJ.4 with `+proj=merc +lat_ts=29.1333
> +lon_0=-89.583333 +k=0.000000 +x_0=100 +y_0=-2972000 +ellps=WGS84
> +datum=WGS84 +units=m +no_defs '

The above should generate an error:

projection initialization failure
cause: k <= 0

Even when lat_ts is specified.  This is because k_0= (or k=) is always sampled 
independent of projection and generate in error when value is <= 0.

In the case of proj=merc, lat_ts= when specified overides any specification of 

lat_ts is commonly used on navigation charts.  If k_0 is used, I suspect it is 
only used in trans-equator maps.

Jerry and the low-riders: Daisy Mae and Joshua
"Cogito cogito ergo cogito sum"
   Ambrose Bierce, The Devil's Dictionary

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