Revision: 5993
http://matplotlib.svn.sourceforge.net/matplotlib/?rev=5993&view=rev
Author: jswhit
Date: 2008-08-07 18:08:25 +0000 (Thu, 07 Aug 2008)
Log Message:
-----------
update comments.
Modified Paths:
--------------
trunk/toolkits/basemap/examples/testgdal.py
Modified: trunk/toolkits/basemap/examples/testgdal.py
===================================================================
--- trunk/toolkits/basemap/examples/testgdal.py 2008-08-07 18:05:34 UTC (rev
5992)
+++ trunk/toolkits/basemap/examples/testgdal.py 2008-08-07 18:08:25 UTC (rev
5993)
@@ -8,9 +8,8 @@
import matplotlib.pyplot as plt
from numpy import ma
-# read DEM file using gdal.
+# read 2.5 minute U.S. DEM file using gdal.
gd = gdal.Open('us_25m.dem')
-# get data from DEM file
array = gd.ReadAsArray()
# get lat/lon coordinates from DEM file.
coords = gd.GetGeoTransform()
@@ -19,14 +18,18 @@
delon = coords[1]
delat = coords[5]
lons = coords[0] + delon*np.arange(nlons)
-lats = coords[3] + delat*np.arange(nlats)[::-1]
+lats = coords[3] + delat*np.arange(nlats)[::-1] # reverse lats
# setup basemap instance.
m = Basemap(llcrnrlon=-119,llcrnrlat=22,urcrnrlon=-64,urcrnrlat=49,
projection='lcc',lat_1=33,lat_2=45,lon_0=-95)
-# transform to nx x ny regularly spaced (4 km) native projection grid
+# create masked array, reversing data in latitude direction
+# (so that data is oriented in increasing latitude, as transform_scalar
+topoin = ma.masked_values(array[::-1,:],-999.)
+# requires).
+# transform DEM dadta to a 4 km native projection grid
nx = int((m.xmax-m.xmin)/4000.)+1; ny = int((m.ymax-m.ymin)/4000.)+1
-topoin = ma.masked_values(array[::-1,:],-999.)
topodat = m.transform_scalar(topoin,lons,lats,nx,ny,masked=True)
+# plot DEM image on map.
im = m.imshow(topodat,cmap=cm.GMT_haxby_r)
# draw meridians and parallels.
m.drawparallels(np.arange(25,65,20),labels=[1,0,0,0])
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