Spherical formula to calculate distance between 2 Longitude and Latitude points is as follows (in miles):
=3963*ACOS(
SIN([@Lat]/57.2957795130823)
* SIN(POI[Latitude]/57.2957795130823)
+ COS([@Lat]/57.2957795130823)
* COS(POI[Latitude]/57.2957795130823)
* COS((POI[Longitude]-[@Lon])/57.2957795130823))
The above formula works in Excel, but not in DAX.