Map Co-ordinates

This is a demonstration program to convert GPS degrees to pixel positions on a map. It is currently in AWK. The most efficient way to convert to a map which uses UTM or a co-ordinate system which is not GPS is to rescale the map image itself.

# Use co-ordinates from the Bottom Left and Top Right of the map:
#
#                         +--------+  Lat 51.453, Lon -2.592
#                         |        |  (120, -159)
#                         |        |
#                         |        |
#                         |        |
# Lat 51.448, Lon -2.602  |        |
#            (-119, 160)  +--------+

# Define the constants once at the start
BEGIN {

# Flash screen in pixels (240 x 320)
BottomLeftX = -119
BottomLeftY = 160
TopRightX = 120
TopRightY = -159

# Map in Lat, Lon
BottomLeftLat = 51.448
BottomLeftLon = -2.602
TopRightLat = 51.453
TopRightLon = -2.592

# Use these in the calculation
ScaleX = (TopRightX - BottomLeftX) / (TopRightLon - BottomLeftLon)
ScaleY = (TopRightY - BottomLeftY) / (TopRightLat - BottomLeftLat)
}
# End constant initialisation

# Given Lon and Lat we can calculate X and Y
{
Lat = $1; Lon = $2;
X = (Lon - BottomLeftLon) * ScaleX + BottomLeftX
Y = (Lat - BottomLeftLat) * ScaleY + BottomLeftY
print X,Y;
}