pro read_poam,dayno,latpos,lonpos,aztop=aztop,dir=dir
;+
; this routine reads the poam data file
;
;  dir = directory where the data is located
;  dayno is the daynumber of the day
;  latpos = the latitude positon
;  lonpos = the longitude position
;  aztop is the azimuth to the point
;
;Variable 2:      Event date year
;Variable 3:      Event date month
;Variable 4:      Event date day
;Variable 7:      Event date seconds
;Variable 11:     Latitude of subtangent point at 20 km altitude
;Variable 12:     Longitude of subtangent point
;Variable 15:     Latitude of spacecraft projected on the surface
;Variable 16:     Longitude of spacecraft projected on the surface
;Variable 17:     Azimuth to spacecraft (blank)
;-

get_lun,unit
year=1900 & mon=0 & day=0 
sec=0.0  & latsx=0. & lons=0.
aztosp=0. 
dayno=double([0.])
latpos=double([0.])
lonpos=double([0.])
aztop=double([0.])
i=0
openr,unit,dir+'poam3_latlon.txt'
while not eof(unit) do begin

   readf,unit,year,mon,day,sec,latsx,lons,aztosp
      if mon le 9 then strmon='0'+str(mon) else strmon=str(mon)
      if day le 9 then strday='0'+str(day) else strday=str(day)
   strdate=string(fix(year),format='(i4)')+strmon + strday
      dayno=[dayno,double(day1900(strdate))+ double(sec)/86400.]
      latpos=[latpos,double(latsx)]
      lonpos=[lonpos,double(lons)]
      aztop=[aztop,double(aztosp)]
      i=i+1
      if i gt 2395 then goto,skip
      end
skip:
      dayno=dayno(1:*)
      latpos=latpos(1:*)
      lonpos=lonpos(1:*)
      aztop=aztop(1:*)
      free_lun,unit
      
      return
end