# Thread: How to Caluculate Lat/Lon from Polar Stereo Maps

1. ## How to Caluculate Lat/Lon from Polar Stereo Maps

I would like to know that how to implementation to show the Latitude and Longiitude with mouse move on north-polar stereo map (WKID : 102018) and south-polar stereo map (WKID : 102021) other than calling a geometry service.

I have tried the below code, but can't get correct value.
Please teach me a correct expression.

Code:
```        private void map1_MouseMove(object sender, MouseEventArgs e)
{
if (map1.SpatialReference.WKID == 102018)
{
System.Windows.Point screenPoint = e.GetPosition(map1);
MapPoint mapPoint = map1.ScreenToMap(screenPoint);

Double p = Math.Sqrt((mapPoint.Y * mapPoint.Y) + (mapPoint.X * mapPoint.X));
Double lat = Math.Acos(mapPoint.X / p);
lat = lat * 180 / Math.PI + 90;

Double lon = Math.PI / 2 - Math.Atan(p / (2 * 6378.137 * 1000));
lon = lon * 180 / Math.PI / 2;

LatitudeTextBlock.Text = string.Format("Latitude: Y = {0}", lat);
LongiitudeTextBlock.Text = string.Format("Longiitude: X = {0}", lon);
}
}```

2. ## Re: How to Caluculate Lat/Lon from Polar Stereo Maps

It would be much easier to use the geometry service to project the coordinates.

http://help.arcgis.com/en/webapi/sil...tm#MouseCoords

That gives you the coordinates, and you will have to add some code to project the coordinates using:

http://help.arcgis.com/en/webapi/sil...rt.htm#Project

Chris

3. ## Re: How to Caluculate Lat/Lon from Polar Stereo Maps

Thank you for comment.
Your method is much easier, however it is a little bit heavy to show the Latitude and Longitude with mouse move at all time.
I would like to consider to use the geometry service.

Thanks!