I am currently using php to try and write code that will take a start point and end point latitude and longitude coordinate pair in decimal degrees and calculate the latitude and longitude of every vertex at a given interval in meters along the path between the two points.
For example:
I have start coordinates of latitude 43.97076 and longitude 12.72543 and I have an endpoint of latitude 43.969730 and longitude 12.728291. Using mathematical calculations (e.g. haversine formula) written in php, I would retrieve the coordinates between those two points at every 1 meter interval starting at the first coordinate and ending at the end coordinate. I welcome a solution written in any language like python, javascript, etc for an example.
Answer
This is quick and dirty. Most of this was adapted from the following website:
http://www.movable-type.co.uk/scripts/latlong.html
I haven't tested this too much but it seemed to work after initial testing. It will return a list of lat, long coordinate pairs along a line at a specified interval. I wrote it in python since I don't know php very well.
from math import cos, sin, atan2, sqrt, radians, degrees, asin, modf
def getPathLength(lat1,lng1,lat2,lng2):
'''calculates the distance between two lat, long coordinate pairs'''
R = 6371000 # radius of earth in m
lat1rads = radians(lat1)
lat2rads = radians(lat2)
deltaLat = radians((lat2-lat1))
deltaLng = radians((lng2-lng1))
a = sin(deltaLat/2) * sin(deltaLat/2) + cos(lat1rads) *
cos(lat2rads) * sin(deltaLng/2) * sin(deltaLng/2)
c = 2 * atan2(sqrt(a), sqrt(1-a))
d = R * c
return d
def getDestinationLatLong(lat,lng,azimuth,distance):
'''returns the lat an long of destination point
given the start lat, long, aziuth, and distance'''
R = 6378.1 #Radius of the Earth in km
brng = radians(azimuth) #Bearing is degrees converted to radians.
d = distance/1000 #Distance m converted to km
lat1 = radians(lat) #Current dd lat point converted to radians
lon1 = radians(lng) #Current dd long point converted to radians
lat2 = asin( sin(lat1) * cos(d/R) + cos(lat1)* sin(d/R)* cos(brng))
lon2 = lon1 + atan2(sin(brng) * sin(d/R)* cos(lat1),
cos(d/R)- sin(lat1)* sin(lat2))
#convert back to degrees
lat2 = degrees(lat2)
lon2 = degrees(lon2)
return[lat2, lon2]
def main(interval,azimuth,lat1,lng1,lat2,lng2):
'''returns every coordinate pair inbetween two coordinate
pairs given the desired interval'''
coords = []
d = getPathLength(lat1,lng1,lat2,lng2)
remainder, dist = modf((d / interval))
counter = 1.0
coords.append([lat1,lng1])
for distance in xrange(1,int(dist)):
c = getDestinationLatLong(lat1,lng1,azimuth,counter)
counter += 1.0
coords.append(c)
counter +=1
coords.append([lat2,lng2])
return coords
if __name__ == "__main__":
#point interval in meters
interval = 1
#direction of line in degrees
azimuth = 279.91
#start point
lat1 = 41.97809
lng1 = -91.65573
#end point
lat2 = 41.97834
lng2 = -91.65767
coords = main(interval,azimuth,lat1,lng1,lat2,lng2)
print coords
I hope this helps. sorry if not. :)
Ok, I added the ability for it to calculate the azimuth for you. I tested with the same location you were using and it turned out perfectly.http://www.darrinward.com/lat-long/?id=705140
import math
def getPathLength(lat1,lng1,lat2,lng2):
'''calculates the distance between two lat, long coordinate pairs'''
R = 6371000 # radius of earth in m
lat1rads = math.radians(lat1)
lat2rads = math.radians(lat2)
deltaLat = math.radians((lat2-lat1))
deltaLng = math.radians((lng2-lng1))
a = math.sin(deltaLat/2) * math.sin(deltaLat/2) + math.cos(lat1rads) * math.cos(lat2rads) * math.sin(deltaLng/2) * math.sin(deltaLng/2)
c = 2 * math.atan2(math.sqrt(a), math.sqrt(1-a))
d = R * c
return d
def getDestinationLatLong(lat,lng,azimuth,distance):
'''returns the lat an long of destination point
given the start lat, long, aziuth, and distance'''
R = 6378.1 #Radius of the Earth in km
brng = math.radians(azimuth) #Bearing is degrees converted to radians.
d = distance/1000 #Distance m converted to km
lat1 = math.radians(lat) #Current dd lat point converted to radians
lon1 = math.radians(lng) #Current dd long point converted to radians
lat2 = math.asin(math.sin(lat1) * math.cos(d/R) + math.cos(lat1)* math.sin(d/R)* math.cos(brng))
lon2 = lon1 + math.atan2(math.sin(brng) * math.sin(d/R)* math.cos(lat1), math.cos(d/R)- math.sin(lat1)* math.sin(lat2))
#convert back to degrees
lat2 = math.degrees(lat2)
lon2 = math.degrees(lon2)
return[lat2, lon2]
def calculateBearing(lat1,lng1,lat2,lng2):
'''calculates the azimuth in degrees from start point to end point'''
startLat = math.radians(lat1)
startLong = math.radians(lng1)
endLat = math.radians(lat2)
endLong = math.radians(lng2)
dLong = endLong - startLong
dPhi = math.log(math.tan(endLat/2.0+math.pi/4.0)/math.tan(startLat/2.0+math.pi/4.0))
if abs(dLong) > math.pi:
if dLong > 0.0:
dLong = -(2.0 * math.pi - dLong)
else:
dLong = (2.0 * math.pi + dLong)
bearing = (math.degrees(math.atan2(dLong, dPhi)) + 360.0) % 360.0;
return bearing
def main(interval,azimuth,lat1,lng1,lat2,lng2):
'''returns every coordinate pair inbetween two coordinate
pairs given the desired interval'''
d = getPathLength(lat1,lng1,lat2,lng2)
remainder, dist = math.modf((d / interval))
counter = float(interval)
coords = []
coords.append([lat1,lng1])
for distance in xrange(0,int(dist)):
coord = getDestinationLatLong(lat1,lng1,azimuth,counter)
counter = counter + float(interval)
coords.append(coord)
coords.append([lat2,lng2])
return coords
if __name__ == "__main__":
#point interval in meters
interval = 1.0
#direction of line in degrees
#start point
lat1 = 43.97076
lng1 = 12.72543
#end point
lat2 = 43.969730
lng2 = 12.728294
azimuth = calculateBearing(lat1,lng1,lat2,lng2)
print azimuth
coords = main(interval,azimuth,lat1,lng1,lat2,lng2)
print coords
I think I have fixed the bugs from the original and it should work (including change the interval). Let me know how it turns out.
No comments:
Post a Comment