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#!/usr/bin/env python3
############################################################################
#
# MODULE: m.distance
#
# AUTHOR(S): Hamish Bowman, Dunedin, New Zealand
# Updated for Ctypes by Martin Landa <landa.martin gmail.com>
#
# PURPOSE: Find distance between two points
# If the projection is latitude-longitude, this distance
# is measured along the geodesic.
# Demonstrates GRASS Python Ctypes interface
#
# COPYRIGHT: (c) 2008-2011 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.
#
############################################################################
#
# Requires GRASS Python Ctypes interface
# Requires Numeric module (NumPy) from http://numpy.scipy.org/
#
# %module
# % label: Finds the distance between two or more points.
# % description: If the projection is latitude-longitude, this distance is measured along the geodesic.
# % keyword: miscellaneous
# % keyword: distance
# % keyword: measure
# %end
# %option
# % key: coord
# % type: string
# % required: yes
# % multiple: yes
# % key_desc: easting,northing
# % description: Comma separated list of coordinate pairs
# %end
# %flag
# % key: i
# % description: Read coordinate pairs from stdin
# % suppress_required: yes
# %end
import sys
import grass.script as gs
from grass.lib.gis import *
def main():
G_gisinit("m.distance")
# calc distance
proj_type = 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.
coords = []
if flags["i"]:
# read line by line from stdin
while True:
line = sys.stdin.readline().strip()
if not line: # EOF
break
else:
coords.append(line.split(","))
else:
# read from coord= command line option
p = None
for c in options["coord"].split(","):
if not p:
p = [c]
else:
p.append(c)
coords.append(p)
p = None
if len(coords) < 2:
gs.fatal("A minimum of two input coordinate pairs are needed")
# init variables
overall_distance = 0.0
coord_array = c_double * len(coords)
x = coord_array()
y = coord_array()
if proj_type == 2:
# lat/lon scan for DDD:MM:SS.SSSS
easting = c_double()
northing = c_double()
G_scan_easting(coords[0][0], byref(easting), PROJECTION_LL)
G_scan_northing(coords[0][1], byref(northing), PROJECTION_LL)
x[0] = float(easting.value)
y[0] = float(northing.value)
else:
# plain coordinates
x[0] = float(coords[0][0])
y[0] = float(coords[0][1])
for i in range(1, len(coords)):
if proj_type == 2:
easting = c_double()
northing = c_double()
G_scan_easting(coords[i][0], byref(easting), PROJECTION_LL)
G_scan_northing(coords[i][1], byref(northing), PROJECTION_LL)
x[i] = float(easting.value)
y[i] = float(northing.value)
else:
x[i] = float(coords[i][0])
y[i] = float(coords[i][1])
segment_distance = G_distance(x[i - 1], y[i - 1], x[i], y[i])
overall_distance += segment_distance
print("segment %d distance is %.2f meters" % (i, segment_distance))
# add to the area array
print("\ntotal distance is %.2f meters\n" % overall_distance)
# calc area
if len(coords) < 3:
return 0
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)
area = G_area_of_polygon(x, y, len(coords))
print("area is %.2f square meters\n" % area)
# we don't need this, but just to have a look
if proj_type == 1:
G_database_units_to_meters_factor()
gs.message("Location units are %s" % G_database_unit_name(True).lower())
return 0
if __name__ == "__main__":
options, flags = gs.parser()
sys.exit(main())
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