pro ulf_read_gps, $
   filepath

;open the data file:
dat_fh = 1
openr, dat_fh, filepath, /get_lun ;open the data file

;read the GPS NMEA header
;example:
;$GPRMC,084222,A,7803.6598,N,01337.2191,E,0.000,0.0,310813,2.9,E*78
;RMC          recommended mimimum sentence C
;084222       fix taken at 08:24:22
;A            status: a active; v void
;7803.6598,N  lat - 78 deg. 03.6598' N
;01337.2191,E lon - 13 deg. 37.2191' E
;0.000        speed
;0.0          track angle
;310813       date - 31 of August, 2013
;2.9,E        magnetic variation
;*78          checksum
nmea_string = string('')
readf, dat_fh, nmea_string
point_lun, dat_fh, 0
print, nmea_string
;parse date, time, latitude, longitude from the NMEA string
nmea_chars = strarr(strlen(nmea_string))
for i=0, strlen(nmea_string) - 1 do begin
    nmea_chars(i) = strmid(nmea_string, i, 1)
endfor
delim = where(nmea_chars eq ',')
timestr = strmid(nmea_string, delim(0)+1, 6)
datestr = strmid(nmea_string, delim(8)+1, 6)

print, datestr + ' ' + timestr
end