KashBird is using following calculation methods
(1) Extracting Latitude, Longitude and Altitude
from Elevation Data
(2) Conversion to Geocentric Coordinate System
(3) Datum Conversion
(4) Conversion to Local Coordinate System
(5) Conversion to Eye-point coordinate Sysytem
(6) Projection to the Screen with Z buffer
method
Appearance Altitude Calculation
Refraction by air is approximated by equivalent earth radius analogue
to the Kashmir.
Distance Calculation
Hybeny's method
Azimuth Calculation
Hybeny's method