4.271.35 void set_position
void set_position(int32_t latitude, int32_t longitude)
Set the geographic coordinates of the 'observer', for use with several of the following functions. Parameters are passed as seconds of North Latitude, and seconds of East Longitude.
For New York City...
set_position( 40.7142 * ONE_DEGREE, -74.0064 * ONE_DEGREE);