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Converting Lambert Projection Clarke1866 Coords to Latitude / Longitude
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Converting Lambert Projection Clarke1866 Coords to Latitude / Longitude splodge 01-28-2006
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Posted by splodge on January 28, 2006, 3:55 am
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 Hi

I'm trying to convert a large set of coastal data-points for Russia
which I've downloaded from the addresses

http://www.maproom.psu.edu/cgi-bin/ian/points/point10.cgi?country=russia1
http://www.maproom.psu.edu/cgi-bin/ian/points/point10.cgi?country=russia2
http://www.maproom.psu.edu/cgi-bin/ian/points/point10.cgi?country=russia3

(it's split into 3 data sets).

The problem is that these co-ordinates are in the following projection.

Projection LAMBERT
Units METERS
Spheroid CLARKE1866
Parameters
1st standard parallel 70 0 0.000
2nd standard parallel 50 0 0.000
central meridian 110 0 0.00
latitude of projection's origin 0 0 0.000
false easting (meters) 0.00000
false northing (meters) 0.00000

according to the site's FAQ
http://www.maproom.psu.edu/dcw/faq/ques6.html

I want Latitude and Longitude co-ordinates. I have already mailed the
site to ask how to convert the co-ordinates but they didn't know.

Searching around I found a piece of code in another posting on this
group
(http://groups.google.co.uk/group/comp.infosystems.gis/browse_frm/thread/eeb540d76692cc60?tvc=1&q=Converting+Lambert+Map+Project+to+Latitude+Lat&hl=en
)

which provides a method for calculating based on the Clarke1866 Spheroi
an there was some code given which required the parameters

sb0 = ??????; /* SINE OF THE TRUE ORIGIN'S LATITUDE (no units)
*/
rbzero = ??????; /* MAPPING RADIUS AT THE TRUE ORIGIN (distance)
*/
nbzero = ??????; /* NORTHING VALUE FOR THE TRUE ORIGIN (distance)
*/
e0 = ??????; /* EASTING VALUE AT THE CENTRAL MERIDIAN (distance)

*/
r_eq = ??????; /* MAPPING RADIUS AT THE EQUATOR (distance)
*/
l0 = ??????; /* LONGITUDE AT THE TRUE ORIGIN (radians)
*/

but these parameters don't seem to coincide with the ones I have
available above. What do I need to do about the 1st, 2nd Parallel etc
? How do I fin the Mapping Radius at the true origin ?

Any help much appreciated. I am not familiar with mapping systems but
I'm good with maths. My aim is to find a mathematical formula that I
can use then I'll write some code to convert the data. Alternatively
if anyone knows where I can find Russia coastal Co-ordinates in
Latitude/Longitude that would also help.

Regards, Mark


Posted by jimirwin on January 29, 2006, 12:09 pm
Please log in for more thread options
>
> Searching around I found a piece of code in another posting on this
> group
> <snip>
> but these parameters don't seem to coincide with the ones I have
> available above. What do I need to do about the 1st, 2nd Parallel etc
> ? How do I fin the Mapping Radius at the true origin ?
>

See http://www.ngs.noaa.gov/PUBS_LIB/ManualNOSNGS5.pdf for the document
that the prior posting refered to. It explains how to compute the
algorithm's parameters from the ones you have.

--
Jim Irwin
http://www.holoscenes.com

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