とりあえず出力形式のメモ
NMEA 0183

• http://bg66.soc.i.kyoto-u.ac.jp/forestgps/nmea.html
• http://www.kh-gps.de/nmea-faq.htm

#!ruby
require 'csv'
types = []
CSV.open('WG20070202064854.log', 'r') do |row|
	next if row[0][0] == ?@
	types << row[0]
end
p types.uniq #=> ["$GPGGA", "$GPGSA", "$GPGSV", "$GPRMC", "$GPVTG"]

RMC だけ読めば十分なようだ。