Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 1153
  • Last Modified:

Accurate distance between two GPS coordinates

Hi,

I am having trouble getting an accurate distance between two lat/lon coordinates.  This site, give the correct result which is 2 meters.

http://boulter.com/gps/distance/?from=53.1330940+-1.1843660&to=53.1331060+-1.1843260&units=k

Here is the code I am using :
function distance(lat1, lon1, lat2, lon2, 'K') {
	var radlat1 = Math.PI * lat1/180
	var radlat2 = Math.PI * lat2/180
	var radlon1 = Math.PI * lon1/180
	var radlon2 = Math.PI * lon2/180
	var theta = lon1-lon2
	var radtheta = Math.PI * theta/180
	var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
	dist = Math.acos(dist)
	dist = dist * 180/Math.PI
	dist = dist * 60 * 1.1515
	if (unit=="K") { dist = dist * 1.609344 }
	if (unit=="N") { dist = dist * 0.8684 }
	return dist
}  

Open in new window


This return 2.98 meters as do a lot of other online versions of this calculation. the correct distance is actually 2 meters. Am I missing something?

My coords are :

FROM
53.1330940 -1.1843660
TO
53.1331060 -1.1843260

ANy help appreciated!
Thanks
0
jellydeal
Asked:
jellydeal
2 Solutions
 
Kim WalkerWeb Programmer/TechnicianCommented:
I would guess there's some rounding taking place on the site you've linked to. The same site measures the distance as 9 feet which is about 2.75 meters. Are you sure your coordinates are accurate?
0
 
Scott Fell, EE MVEDeveloper & EE ModeratorCommented:
That site is just rounding.   I have code below that comes up with 1.8.  Maybe I have the points off?

http://jsbin.com/vumikayi/1/edit

//:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
//:::                                                                         :::
//:::  This routine calculates the distance between two points (given the     :::
//:::  latitude/longitude of those points). It is being used to calculate     :::
//:::  the distance between two locations using GeoDataSource (TM) prodducts  :::
//:::                                                                         :::
//:::  Definitions:                                                           :::
//:::    South latitudes are negative, east longitudes are positive           :::
//:::                                                                         :::
//:::  Passed to function:                                                    :::
//:::    lat1, lon1 = Latitude and Longitude of point 1 (in decimal degrees)  :::
//:::    lat2, lon2 = Latitude and Longitude of point 2 (in decimal degrees)  :::
//:::    unit = the unit you desire for results                               :::
//:::           where: 'M' is statute miles                                   :::
//:::                  'K' is kilometers (default)                            :::
//:::                  'N' is nautical miles                                  :::
//:::                                                                         :::
//:::  Worldwide cities and other features databases with latitude longitude  :::
//:::  are available at http://www.geodatasource.com                          :::
//:::                                                                         :::
//:::  For enquiries, please contact sales@geodatasource.com                  :::
//:::                                                                         :::
//:::  Official Web site: http://www.geodatasource.com                        :::
//:::                                                                         :::
//:::               GeoDataSource.com (C) All Rights Reserved 2014            :::
//:::                                                                         :::
//:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

function distance(lat1, lon1, lat2, lon2, unit) {
	var radlat1 = Math.PI * lat1/180
	var radlat2 = Math.PI * lat2/180
	var radlon1 = Math.PI * lon1/180
	var radlon2 = Math.PI * lon2/180
	var theta = lon1-lon2
	var radtheta = Math.PI * theta/180
	var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
	dist = Math.acos(dist)
	dist = dist * 180/Math.PI
	dist = dist * 60 * 1.1515
	if (unit=="K") { dist = dist * 1.609344 }
	if (unit=="N") { dist = dist * 0.8684 }
	return dist
}       
/*
53.1330940 -1.1843660
TO
53.1331060 -1.1843260
*/
var lat1=53.1330940;
var lon1=-1.1843660;
 
var lat2=53.1331060;
var lon2=-1.1843260;

var kilometers=distance(lat1, lon1, lat2, lon2, 'k'); 
meters = kilometers*1000
alert(meters);

Open in new window

0

Featured Post

Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now