coordinate transformations formulas ... ?

Manfred Meier m.meier at SPIEKERMANN.DE
Fri Feb 10 23:18:30 EST 2006


Hello,

I had a similar problem. What programming language do you use? I had 
trouble with some double to float or double to long conversion (done by 
the compiler) because i declared some variables not appropriate.

Manfred


Janeks Kamerovskis schrieb:
> Yes and I tested, that I can safely ignore those ..., because they have
> realy small influence on result.
> But the next problem is that I can get those example value for M an M0. They
> are sligtly different for the given example (from EPSG quidance
> http://www.epsg.org/guides/docs/G7-2.pdf) it differs by some cople of
> thousands (5596050.46000000 5602234.40780535 and 5429228.60000000
> 5435961.03820551)
> I checked many of the sources of Transverse Mercator formulas description
> (EPSG of course and other) they all looked the same.
> I checked my implementations of formulas not only twice, but the result is
> the same.
> 
> Janeks
> P.S. Sorry about looking like offtopic - you could ask why I need to
> implement things that already has in proj4. I just have a case, when it is
> difficult to use, but finaly data any way will come to Mapserver.
> 
> 
>>-----Original Message-----
>>From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
>>Behalf Of Stephen Woodbridge
>>Sent: Wednesday, February 08, 2006 5:00 PM
>>To: MAPSERVER-USERS at LISTS.UMN.EDU
>>Subject: Re: [UMN_MAPSERVER-USERS] coordinate transformations formulas ...
>>?
>>
>>The ... means "and additional terms following the sequence of the prior
>>terms". It is basically a short hand notation for a summation of n to
>>infinity. So you if you want more terms you need to first infer the
>>sequence from the prior terms like [2, 4, 6, ...] is a sequence and the
>>next terms are  8, 16, 32, ...
>>
>>Each additional term adds some additional fractional accuracy to the
>>computation, at some point the fractional accuracy is beyond the point
>>that it is significant to to our uses.
>>
>>If you calculate just the 3rd term and see how big its value is it will
>>give you the magnitude of the change it is impacting on the equation and
>>the next term in the sequence will tern to be significantly smaller.
>>
>>-Steve W.
>>
>>Janeks Kamerovskis wrote:
>>
>>>
>>>Hi list,
>>>
>>>
>>>
>>>What means those ... in the formula, that is part of coordinate
>>>transformations formulas?
>>>
>>>
>>>
>>>M = a[(1 - e2/4 - 3e4/64 - 5e6/256 -....)j - (3e2/8 + 3e4/32 +
>>>45e6/1024+....)sin2j + (15e4/256 + 45e6/1024 +.....)sin4j - (35e6/3072 +
>>>....)sin6j + .....]
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>brgds
>>>
>>>Janeks
>>>
>>>
>>>
> 
> 



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