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Re: Any way to initialize mapping in IDL with WKT or a Proj.4 string? [message #93692 is a reply to message #93685]

Fri, 30 September 2016 14:31

Gordon Farquharson
Messages: 48
Registered: December 2010

Member

OK, so here is a solution. It can be extended to deal with any projection IDL knows about. Thank you, Exelis/Harris for implementing the IDL-Python bridge. Very useful.

For this solution to work, you need to have the IDL-Python bridge working and have the Python API for GDAL/OGR installed.

FUNCTION map_proj_init_proj4, proj4_string

compile_opt IDL2, LOGICAL_PREDICATE, STRICTARRSUBS

osr = python.import('osgeo.osr')
srs = osr.SpatialReference()
IF osr.SpatialReference.ImportFromProj4(srs, proj4_string) NE 0 THEN BEGIN
message, 'error importing from Proj.4 string'
ENDIF

CASE 1 OF

proj4_string.matches('\+proj=utm'): BEGIN
semimajor_axis = osr.SpatialReference.GetSemiMajor(srs)
semiminor_axis = osr.SpatialReference.GetSemiMinor(srs)
utm_zone = osr.SpatialReference.GetUTMZone(srs)
map = map_proj_init(101, $
SEMIMAJOR_AXIS=semimajor_axis, $
SEMIMINOR_AXIS=semiminor_axis, $
ZONE=utm_zone)
END

ELSE: BEGIN
message, 'projection not recognized'
END

ENDCASE

return, map

END

Usage:

IDL> map_struct = map_proj_init_proj4('+proj=utm +zone=10 +ellps=WGS84 +datum=WGS84 +units=m +no_defs')
IDL> print, map_proj_forward(-122, 42, MAP=map_struct), FORMAT='(2(F20.9))'
582818.069248419 4650259.847758290

(The UTM/GCTP bug [1] seems to be fixed in IDL 8.5.1.)

Gordon

[1] http://www.idlcoyote.com/map_tips/utmwrong.php

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[Message index]

		Any way to initialize mapping in IDL with WKT or a Proj.4 string? By: Gordon Farquharson on Thu, 29 September 2016 15:20
		Re: Any way to initialize mapping in IDL with WKT or a Proj.4 string? By: rawahranger on Thu, 29 September 2016 21:22
		Re: Any way to initialize mapping in IDL with WKT or a Proj.4 string? By: Gordon Farquharson on Fri, 30 September 2016 14:31
		Re: Any way to initialize mapping in IDL with WKT or a Proj.4 string? By: Gordon Farquharson on Sun, 16 October 2016 19:41

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