function latlon2xyz,location,depth,a
;location[0]=lat in radians
;location[1]=lon in radians
;depth in meters
;a=radius of earth, or if a<=0, use GRS80

if n_params() eq 1 then begin
  depth=0
  a=0
endif else if n_params() eq 2 then a=0

if a le 0 then begin
   a=6378137d
   f=1/298.257222101d
   esquared=2*f-f^2
endif else esquared=0d

n=a/sqrt(1-(esquared*sin(location[0])^2))
x=(n-depth)*cos(location[0])*cos(location[1])
y=(n-depth)*cos(location[0])*sin(location[1])
z=(n*(1-esquared)-depth)*sin(location[0])

return,[x,y,z]
end