;Calculate the size needed for a polar lambert projection map array.
;
;Input
;  kmperpix - Typical size of a map pixel, in km. Each map pixel will have
;             an area as close as possible to kmperpix^2 km^2. Map pixels
;             close to the pole will be almost square kmperpix km on a side,
;             while pixels close to the edge of the map will be more rectangular
;             Since it is an equal area projection, all pixels will have the exact
;             same area.
;  minmaplat - Southernmost latitude of the map, in degrees.
;
;Output
;  maxrho -
function map_size_lambert,kmperpix=kmperpix, minmaplat=minmaplat,maxrho=maxrho
  if n_elements(minmaplat) eq 0 then minmaplat=30
  if n_elements(kmperpix) eq 0 then kmperpix=5

  ;Screen extent of our image in pixels (make sure it's even)
  maxrho=2d*sin((90d -minmaplat)/2*!const.dtor)
  return,floor(0.5+2d*get_wgs84_const(/re)*sin((90d -minmaplat)/2*!const.dtor)/kmperpix)*2
end