K’s Lair

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.1">
<NetworkLink>
	<name>GPS</name>
	<flyToView>1</flyToView>
	<Url>
		<href>/tmp/posdata.kml</href>
		<refreshMode>onInterval</refreshMode>
		<refreshInterval>10</refreshInterval>
	</Url>
</NetworkLink>
</kml>

#!/usr/bin/python
"""
Script to read nmea data from a GPS mouse
Copyright (C) 2008  Andreas Goelzer
 
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
This program reads data from a nmea device (uses the GGA sentence),
and creates a google kml file with the current position and the path
leading there. Additionally, a gpx file is generated containing the
track data with time information.
"""
 
from serial import Serial;
from time import strftime, gmtime;
from optparse import OptionParser;
 
 
hist = "";
gpx = "";
 
kmlmask="""<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.0">
<Document>
	<Placemark>
		<name>Your Position</name>
		<Point>
			<coordinates>%s</coordinates>
		</Point>
	</Placemark>
	<Placemark>
		<name>Previous positions</name>
		<description>Path that lead you here</description>
		<LineString>
			<coordinates>%s</coordinates>
		</LineString>
	</Placemark>
</Document>
</kml>"""
#			<altitudeMode>absolute</altitudeMode>
 
gpxmask = """<?xml version="1.0" encoding="UTF-8" standalone="no" ?><gpx xmlns="http://www.topografix.com/GPX/1/1" xmlns:gpxx="http://www.garmin.com/xmlschemas/GpxExtensions/v3" xmlns:gpxtpx="http://www.garmin.com/xmlschemas/TrackPointExtension/v1" creator="Colorado 300" version="1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd http://www.garmin.com/xmlschemas/GpxExtensions/v3 http://www.garmin.com/xmlschemas/GpxExtensions/v3/GpxExtensionsv3.xsd http://www.garmin.com/xmlschemas/TrackPointExtension/v1 http://www.garmin.com/xmlschemas/TrackPointExtension/v1/TrackPointExtensionv1.xsd">
<trk><name>%s</name><trkseg>%s</trkseg></trk></gpx>"""
 
def gpstime():
	return strftime("%Y-%m-%dT%H:%M:%SZ",gmtime());
 
def readlatlon(value,inverse):
	lat = float(value);
	lat2 = int(lat) / 100;
	lat = lat2 + (lat - 100 * lat2)/ 60; 
	if inverse:
		lat = -lat;
	return lat;
 
def calcchecksum(checkstr):
	cs = ord(checkstr[0]);
	for i in range(1,len(checkstr)):
		cs ^= ord(checkstr[i])
	return cs;
 
 
class sentencevalidator:
	"Check checksum and other stuff and split to fields"
	def __init__(self,line):
		if(line[0] == '$' and line[-5] == '*' and calcchecksum(line[1:-5]) ==  int(line[-4:-2],16)):
			self.valid = True;
			self.sentence = line[3:6];
			self.data = line[7:-5].split(',');
		else :
			self.valid = False;
 
parser = OptionParser(version="%prog 0.1");
parser.add_option("-s", "--serial", dest="serial",
                  help="serial terminal of the gps unit", default='/dev/ttyUSB0', metavar="FILE");
parser.add_option("-g", "--gpxfile", dest="gpxfile",
                  help="GPX output file", default="/tmp/track" + gpstime() + ".gpx", metavar="FILE");
parser.add_option("-k", "--kmlfile", dest="kmlfile",
                  help="KML output file", default="/tmp/posdata.kml", metavar="FILE");
parser.add_option("-v", "--verbose",
                  action="store_true", dest="verbose", default=False,
                  help="print debug messages");
 
(options, args) = parser.parse_args();
 
gps = Serial(options.serial, 4800, timeout=1);
 
 
#on sirf chips, activate all sentences
for i in range(1,5):
	cmd = "PSRF103,0%d,00,05,01" % i;
	realcmd="$%s*%x\r\n" % (cmd,calcchecksum(cmd));
	print realcmd;
	gps.write(realcmd)
 
try:
	while 1:
		line = gps.readline()
		if(options.verbose): print line,
		s = sentencevalidator(line);
		if(s.valid and s.sentence == "GGA" and int(s.data[5]) != 0):
			lat = readlatlon(s.data[1],s.data[2]=='S');
			lon = readlatlon(s.data[3],s.data[4]=='W');
			alt = float(s.data[8]);
 
			gpx += "\n" + '<trkpt lat="%f" lon="%f"><ele>%f</ele><time>%s</time></trkpt>' % (lon,lat,alt,gpstime())
 
			position =  "%f, %f, %f" % (lon,lat,alt);
			print position
			hist += "\n" + position;
			f=open("/tmp/posdata.kml",'w');
			f.write(kmlmask % (position,hist));
			f.close();
 
except:
	0
 
f=open(options.gpxfile,'w');
f.write(gpxmask % (gpstime(),gpx));
f.close();
 
gps.close()