[Proj] Info on proj4 formulas

Mikhail Tchernychev misha at mail.geometrics.com
Fri May 9 13:28:40 EST 2014

Well, it seems to me first part of your letter contradicts (1) and (2).

Anyway, if there is negligible difference (say in order of cm) than what 
could come wrong friendly fire or drilling?

But I have to admit that consequences could be severe for surveyor in 
two cases:

1. there is a legal requirement to use specific formulas.  In this case 
we are in trouble
even the formulas yield exactly the same results but not recommended 
ones were used.

2. If required formulas were distorted on purpose.   Then this is just a 
case of classified information.

Best Regards,

On 5/9/2014 10:59 AM, Clifford J Mugnier wrote:
> Variations in projection formulae can be an academic exercise or a catastrophe, depending on the application.  Most GIS applications can use practically any truncation of the infinite series (4th order, 5th order, 6th order, etc.) with little to no effect to day-to-day work.  There are two exceptions:
> 1.)	Military.  Always use whatever is currently promulgated by NGA for NATO/SEATO applications.  This helps avoid “friendly fire” incidents among units that provide indirect fire support.
> 2.)	Oil and Gas.  Exploration and Production concessions leased by national governments use map projections for Grid Systems as legal coordinate systems sometimes based on specific truncations.  When that is in effect, the use of other truncations (especially in offshore areas) can produce catastrophic errors in positioning.
> Sometimes, mathematical distortions at various distances from the projection origin are on purpose!
> Cliff Mugnier
> ________________________________________
> From: proj-bounces at lists.maptools.org <proj-bounces at lists.maptools.org> on behalf of Hermann Peifer <peifer at gmx.eu>
> Sent: Friday, May 9, 2014 12:47 PM
> To: PROJ.4 and general Projections Discussions
> Subject: Re: [Proj] Info on proj4 formulas
> On 2014-05-09 16:31, Nick Ves wrote:
>> Intresting,
>> But now I'm wondering if the OGP's "Geomatics Guidance Note Number 7,
>> part 2 Coordinate Conversions and Transformations including Formulas"
>> [0] has been taken into account in the realizations of the formulas.
>> [0] http://www.ogp.org.uk/pubs/373-07-2.pdf
> At least Thomas Flemming mentions an earlier version of the guidance
> note, see http://trac.osgeo.org/proj/browser/trunk/proj/src/PJ_krovak.c
> Hermann
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