[GRASS-SVN] r30447 - in grass/trunk/swig/python: . examples
svn_grass at osgeo.org
svn_grass at osgeo.org
Mon Mar 3 11:59:16 EST 2008
Author: hamish
Date: 2008-03-03 11:59:15 -0500 (Mon, 03 Mar 2008)
New Revision: 30447
Added:
grass/trunk/swig/python/examples/
grass/trunk/swig/python/examples/m.distance
Log:
example m.distance script (fully functional)
Added: grass/trunk/swig/python/examples/m.distance
===================================================================
--- grass/trunk/swig/python/examples/m.distance (rev 0)
+++ grass/trunk/swig/python/examples/m.distance 2008-03-03 16:59:15 UTC (rev 30447)
@@ -0,0 +1,183 @@
+#!/usr/bin/python
+############################################################################
+#
+# MODULE: m.distance
+#
+# AUTHOR(S): Hamish Bowman, Dunedin, New Zealand
+#
+# PURPOSE: Find distance between two points
+# If the projection is latitude-longitude, this distance
+# is measured along the geodesic.
+# Demonstrates GRASS SWIG-Python interface
+#
+# COPYRIGHT: (c) 2008 Hamish Bowman, and The GRASS Development Team
+#
+# This program is free software under the GNU General Public
+# License (>=v2). Read the file COPYING that comes with GRASS
+# for details.
+#
+############################################################################
+
+#%Module
+#% label: Finds the distance between two or more points.
+#% description: If the projection is latitude-longitude, this distance is measured along the geodesic.
+#% keywords: miscellaneous, distance, measure
+#%End
+#%Option
+#% key: coord
+#% type: string
+#% required: no
+#% multiple: yes
+#% key_desc: x,y
+#% description: Comma separated list of coordinate pairs
+#%End
+
+import sys
+import os
+
+def main():
+
+ #### add your code here ####
+
+ # run this before starting python to append module search path:
+ # export PYTHONPATH=/usr/src/grass63/swig/python
+ # check with "import sys; sys.path"
+ # or:
+ sys.path.append("/usr/src/grass/svn/grass63/swig/python")
+ import python_grass6 as g6lib
+
+ # for passing pointers
+ import Numeric
+ import NumPtr
+
+ g6lib.G_gisinit('m.distance')
+ # returns 0 on success
+
+
+ ### calc distance ###
+
+ proj_type = g6lib.G_begin_distance_calculations()
+ # returns 0 if projection has no metrix (ie. imagery)
+ # returns 1 if projection is planimetric
+ # returns 2 if projection is latitude-longitude
+
+
+ # parser always creates at least an empty variable, and sys.argv is
+ # toast, so no way to check if option was given. So it hangs if
+ # --q was the only option given and there is no data from stdin.
+ coord_ans = os.getenv("GIS_OPT_COORD")
+ if coord_ans:
+ # read from coord= command line option
+ coords = coord_ans.split(',')
+ else:
+ # FIXME: this can hang if no input is given
+ coords = []
+ # read line by line from stdin
+ while 1:
+ line = sys.stdin.readline().strip()
+ if not line: # EOF
+ break
+ else:
+ coords += line.split(',')
+
+ if len(coords) < 4:
+ print "A minimum of four input coordinates are needed"
+ return
+
+
+ # init variables
+ overall_distance = 0.0
+
+ if proj_type == 2:
+ # lat/lon scan for DDD:MM:SS.SSSS
+ easting = Numeric.array(0., Numeric.Float64)
+ eastPtr = NumPtr.getpointer(easting)
+ northing = Numeric.array(0., Numeric.Float64)
+ northPtr = NumPtr.getpointer(northing)
+
+ g6lib.G_scan_easting(coords[0], eastPtr, 3)
+ g6lib.G_scan_northing(coords[1], northPtr, 3)
+ x1 = float(easting)
+ y1 = float(northing)
+ else:
+ # plain old coordinates
+ x1 = float(coords[0])
+ y1 = float(coords[1])
+
+ x = [x1]
+ y = [y1]
+
+ for i in range((len(coords) / 2) - 1):
+
+ if proj_type == 2:
+ g6lib.G_scan_easting(coords[ (i+1)*2 + 0 ], eastPtr, 3)
+ g6lib.G_scan_northing(coords[ (i+1)*2 + 1 ], northPtr, 3)
+ x2 = float(easting)
+ y2 = float(northing)
+ else:
+ x2 = float(coords[ (i+1)*2 + 0 ])
+ y2 = float(coords[ (i+1)*2 + 1 ])
+
+ segment_distance = g6lib.G_distance(x1, y1, x2, y2)
+ overall_distance += segment_distance
+
+ print "segment %d distance is %.2f meters" % (i+1, segment_distance)
+
+ # add to the area array
+
+ # setup for the next loop
+ x1 = x2
+ y1 = y2
+
+ x += [x2]
+ y += [y2]
+
+ print
+ print " total distance is %.2f meters" % overall_distance
+ print
+
+
+ ### calc area ###
+ if len(coords) < 6:
+ return
+
+ g6lib.G_begin_polygon_area_calculations()
+ # returns 0 if the projection is not measurable (ie. imagery or xy)
+ # returns 1 if the projection is planimetric (ie. UTM or SP)
+ # returns 2 if the projection is non-planimetric (ie. latitude-longitude)
+
+ # do not need to close polygon (but it doesn't hurt if you do)
+ npoints = len(x)
+
+ # unset variables:
+ #del [Xs, Xptr, Ys, Yptr]
+ # or
+ #Xs = Xptr = Ys = Yptr = None
+
+ Xs = Numeric.array(x, Numeric.Float64)
+ Xptr = NumPtr.getpointer(Xs)
+ Ys = Numeric.array(y, Numeric.Float64)
+ Yptr = NumPtr.getpointer(Ys)
+
+ area = g6lib.G_area_of_polygon(Xptr, Yptr, npoints)
+ print "AREA: %10.2f square meters" % area
+ print
+
+
+ # we don't need this, but just to have a look
+ if False:
+ if proj_type == 1:
+ g6lib.G_database_units_to_meters_factor()
+ # 1.0
+ print "Location units are", g6lib.G_database_unit_name(True)
+
+
+ #### end of your code ####
+ return
+
+if __name__ == "__main__":
+ if ( len(sys.argv) <= 1 or sys.argv[1] != "@ARGS_PARSED@" ):
+ os.execvp("g.parser", [sys.argv[0]] + sys.argv)
+ else:
+ main();
+
Property changes on: grass/trunk/swig/python/examples/m.distance
___________________________________________________________________
Name: svn:executable
+ *
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