Changes between Initial Version and Version 1 of Ticket #4861, comment 2
 Timestamp:
 Jun 19, 2015, 8:43:32 AM (9 years ago)
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Ticket #4861, comment 2
initial v1 4 4 1. The latitude of natural origin for Mercator should always be zero (Equator) by definition, so having OGRSpatialReference::SetMercator() take in the center latitude is problematic. ESRI, EPSG and Proj4 are all consistent on that point as far as I can tell. 5 5 2. ESRI's Mercator is really Mercator 2SP, so it stands to reason that SRS_PT_MERCATOR_2SP should be mapped to it by simply renaming the projection's name. 6 3. The formulas for converting between the scale factor of 1SP to the first standard par ellel of 2SP are as follows for the Mercator projection. See the EPSG Guidance Notes at http://www.iogp.org/pubs/373072.pdf:6 3. The formulas for converting between the scale factor of 1SP to the first standard parallel of 2SP are as follows for the Mercator projection. See the EPSG Guidance Notes at http://www.iogp.org/pubs/373072.pdf: 7 7 8 8 k0:: … … 13 13 ellipsoid's first eccentricity 14 14 15 1SP to 2SP::15 2SP to 1SP:: 16 16 k0 = cos(sp) / sqrt( 1  (e^2^ * sin^2^(sp)) ) 17 17 18 2SP to 1SP::18 1SP to 2SP:: 19 19 sp = acos( sqrt( (1  e^2^) / (1 / k0^2^)  e^2^) ) )