PRO geo2az,glat,glong,ght,slat,slong,sht,az,za,rng,azimuth0=azimuth0

; This routine uses utility routines copied from GEOLB.FOR to
; convert geographic coordinates (degrees) at a specific height
; (km) into look angles (degrees) and range (km) from a specific
; location.  The keyword azimuth0 is the offset (degrees E of N)
; of the azimuth from which the returned azimuths are to be measured.
; It defaults to 0.

IF KEYWORD_SET(azimuth0) THEN az0=azimuth0 ELSE az0=0.
IF N_ELEMENTS(ght) EQ 1 THEN aht=REPLICATE(ght,1,1) ELSE aht=ght
trsk1,glat,glong,aht,x,y,z
trsk2,x,y,z,slat,slong,sht,az0,xp,yp,zp
trsk3,xp,yp,zp,az0,az,el,rng
za=90.0-el
RETURN
END