CODEWITHSUNDEEP
c#algorithmlatitude-longitudeaverage
Evenstar
Evenstar

Reputation: 75

Calculate average latitude and longitude in C#

I have (minLatitude,maxLatitude) and (minLongitude,maxLongitude) pairs in decimal degrees, and I need to calculate the mean point of the box those pairs define, how can I get their average latitude/longitude? I get a pretty big offset when the simple arithmetic mean is calculated.

Thanks!

Upvotes: 4

Views: 3003

Answers (2)

Lior Kogan
Lior Kogan

Reputation: 20618

The solution suggested by Pierre-Luc Champigny is wrong.

In the image bellow you can see two lines:

  1. (lat1,lon1) --> (lat2,lon2)
  2. (lat1,lon2) --> (lat2,lon1)

Half length of each line in green, the other half in blue.

You can see that the center of both lines is not the same point, and both centers are not the center of the polygon.

earth

In order to find the center of the polygon:

  • lat= avrg(lat1,lat2)
  • lon= avrg(lon1,lon2)

To get these values you can use the link suggested by Pierre-Luc Champigny, but:

  • Take the lat of the midpoint of (lat1,lon1) --> (lat2,lon1)
  • Take the lon of the midpoint of (lat1,lon1) --> (lat1,lon2)

Upvotes: 8

Pierre-Luc Champigny
Pierre-Luc Champigny

Reputation: 1851

From: http://www.movable-type.co.uk/scripts/latlong.html

Your values should be all in radian, so using the midpoint formula:

var lat1 = minLatitude;  // In radian
var lat2 = maxLatitude;  // In radian
var lon1 = minLongitude; // In radian
var lon2 = maxLongitude; // In radian

var dLon = (lon2-lon1); 


var Bx = Math.Cos(lat2) * Math.Cos(dLon);
var By = Math.Cos(lat2) * Math.Sin(dLon);
var avgLat = Math.Atan2(
           Math.Sin(lat1) + 
           Math.Sin(lat2), 
           Math.Sqrt((
           Math.Cos(lat1)+Bx) * (Math.Cos(lat1)+Bx) + By*By));

var avgLong = lon1 + Math.Atan2(By, Math.Cos(lat1) + Bx);

Upvotes: 5

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