[Proj] Relationship between transverse Mercator algorithms

Charles Karney ckarney at sarnoff.com
Thu Sep 11 08:56:20 EDT 2008

Mikael Rittri wrote:
>> For each set, define
>>   dxn  = max(error in forward transformation,
>>               discrepancy in forward and reverse transformations)
>>           for nth order method (order e^(2*n))
> Has the nominal error in the forward transformation been divided by
> the local scale factor?

No, the first term does not include the scale factor and so that "max"
is of two dissimilar quantities (a scaled distance and a distance).  So
the table I gave overestimates the errors by up to a factor of 10
particularly for mu (angular distance from central meridian) > 45.  For
mu < 20 the change in the errors will be only about 10%.

I will correct (sometime today or tomorrow) this so that the error is
really meters on the ground.

Charles Karney <ckarney at sarnoff.com>
Sarnoff Corporation, Princeton, NJ 08543-5300

URL: http://charles.karney.info
Tel: +1 609 734 2312
Fax: +1 609 734 2662

More information about the Proj mailing list