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corners.py
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import sys

# Remember kids: x is lon and y is lat!

southwest_lat = float(sys.argv[1])
southwest_lon = float(sys.argv[2])
northeast_lat = float(sys.argv[3])
northeast_lon = float(sys.argv[4])
margin        = float(sys.argv[5])

x_width = northeast_lon - southwest_lon
y_width = northeast_lat - southwest_lat

if x_width/y_width == 2.0:
    new_x_width = x_width*(1 + margin)
    new_y_width = y_width*(1 + margin)

if x_width/y_width > 2.0:
  # make y bigger
  new_x_width = x_width*(1 + margin)
  new_y_width = new_x_width/2.0

if x_width/y_width < 2.0:
  # make x bigger
  new_y_width = y_width*(1 + margin)
  new_x_width = 2.0*new_y_width

#  Finally compute center of original extents:

xc = (northeast_lon + southwest_lon)/2.0
yc = (northeast_lat + southwest_lat)/2.0

#  Compute final extents:

new_northeast_lon = xc + new_x_width/2.0
new_southwest_lon = xc - new_x_width/2.0
new_northeast_lat = yc + new_y_width/2.0
new_southwest_lat = yc - new_y_width/2.0

print "Latitude,Longitude,Name,IconColor,Icon"
#
print "%s,%s,%s,orange,111" % (new_southwest_lat,new_southwest_lon,"new SW corner")
print "%s,%s,%s,orange,111" % (new_northeast_lat,new_southwest_lon,"new NW corner")
print "%s,%s,%s,orange,111" % (new_northeast_lat,new_northeast_lon,"new NE corner")
print "%s,%s,%s,orange,111" % (new_southwest_lat,new_northeast_lon,"new SE corner")
print "%s,%s,%s,red,111" % (southwest_lat,southwest_lon,"old SW corner")
print "%s,%s,%s,red,111" % (northeast_lat,southwest_lon,"old NW corner")
print "%s,%s,%s,red,111" % (northeast_lat,northeast_lon,"old NE corner")
print "%s,%s,%s,red,111" % (southwest_lat,northeast_lon,"old SE corner")
--------------------------------------------------
Test
--------------------------------------------------
#
# El Segundo 4/2/14
#
python ./corners.py 33.905266155474649 -118.39714482432021 33.907727245282345 -118.38229948451819 0.1 > error_corners.csv
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error_corners.csv
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Latitude,Longitude,Name,IconColor,Icon
33.9024142319,-118.397887091,new SW corner,orange,111
33.9105791688,-118.397887091,new NW corner,orange,111
33.9105791688,-118.381557218,new NE corner,orange,111
33.9024142319,-118.381557218,new SE corner,orange,111
33.9052661555,-118.397144824,old SW corner,red,111
33.9077272453,-118.397144824,old NW corner,red,111
33.9077272453,-118.382299485,old NE corner,red,111
33.9052661555,-118.382299485,old SE corner,red,111
--------------------------------------------------