Changeset 22339

Timestamp:

01/05/18 14:45:40 (7 years ago)

Author:

seroussi

Message:

NEW: added scaling_factor option for polar stereographic projections in ll2xy and xy2ll

Location:

issm/trunk-jpl/src/m/coordsystems

Files:

• ll2xy.m (modified) (3 diffs)
• xy2ll.m (modified) (4 diffs)

issm/trunk-jpl/src/m/coordsystems/ll2xy.m

@@ -1 @@
-function [x,y] = ll2xy(lat,lon,sgn,central_meridian,standard_parallel)  
+function [x,y,scale_factor] = ll2xy(lat,lon,sgn,central_meridian,standard_parallel)  
 %LL2XY - converts lat long to polar stereographic
 %
 %   Converts from geodetic latitude and longitude to Polar 
 %   Stereographic (X,Y) coordinates for the polar regions.
+%   Optional scale factor provides the scaling factor needed to correct projection error
+%   in areas and volumes
 %   Author: Michael P. Schodlok, December 2003 (map2ll)
 %
 %   Usage:
 %      [x,y] = ll2xy(lat,lon,sgn)
+%      [x,y,scale_factor] = ll2xy(lat,lon,sgn)
 %      [x,y] = ll2xy(lat,lon,sgn,central_meridian,standard_parallel)
 %
@@ -29 +32 @@
 else
         help ll2xy
+        error('bad usage');
+end
+
+if nargout~=3 & nargout~=2,
+        help xy2ll
         error('bad usage');
 end
@@ -65 +73 @@
         y(cnt1) = 0.0;
 end
+
+if nargout==3,
+        m=((1+sin(abs(slat)*pi/180))*ones(length(lat),1)./(1+sin(abs(lat)*pi/180)));
+        scale_factor=(1./m).^2;
+end

issm/trunk-jpl/src/m/coordsystems/xy2ll.m

@@ -1 @@
-function [lat,lon] = xy2ll(x,y,sgn,central_meridian,standard_parallel)
+function [lat,lon,scale_factor] = xy2ll(x,y,sgn,central_meridian,standard_parallel)
 %XY2LL - converts xy to lat long
 %
@@ -5 +5 @@
 %   latitude and longitude Stereographic (X,Y) coordinates for the polar
 %   regions.
+%   Optional scale factor provides the scaling factor needed to correct projection error
+%   in areas and volumes
 %   Author: Michael P. Schodlok, December 2003 (map2xy.m)
 %
 %   Usage:
 %      [lat,lon] = xy2ll(x,y,sgn);
+%      [lat,lon,scale_factor] = xy2ll(x,y,sgn);
 %      [lat,lon] = xy2ll(x,y,sgn,central_meridian,standard_parallel);
 %
@@ -29 +32 @@
         end
 else
+        help xy2ll
+        error('bad usage');
+end
+
+if nargout~=3 & nargout~=2,
         help xy2ll
         error('bad usage');
@@ -71 +79 @@
 lat = lat * 180. / pi;
 lon = lon - delta; 
+if nargout==3,
+        m=((1+sin(abs(slat)*pi/180))*ones(length(lat),1)./(1+sin(abs(lat)*pi/180)));
+        scale_factor=(1./m).^2;
+end