[GIS] Get coordinates from polygon points on MapBox draw

coordinatesjavascriptmapbox-gl-js

This is the code I am using for polygon to draw and I am using MapBox GL draw I am trying to get longitude and latitude of every point from polygon.

var draw = new MapboxDraw({
  displayControlsDefault: false,
  controls: {
     polygon: true,
     trash: true,
  }
});

map.addControl(draw);

map.on('draw.create', function(e) { 

    if (lngLat.lng && lngLat.lat == 'polygon') {
        console.log(draw.getAll());
    }
});

Best Answer

Try this:

var x=draw.getAll();
console.log(x['features'][0]['geometry']['coordinates'][0]);

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[GIS] Getting all vertex lat, long coordinates every 1 meter between two known points using PHP

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.

[GIS] Get coordinates from drawn items with Mapbox-gl-draw

You could try using Draw.getAll().

It should return a feature collection containing all of the drawn features.

The reference for this is here.

Best Answer

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[GIS] Getting all vertex lat, long coordinates every 1 meter between two known points using PHP

[GIS] Get coordinates from drawn items with Mapbox-gl-draw

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