And that is basically everything to say, enjoy the little applet.

Installation

Make sure gpsd is installed and set up properly. Also make sure the python bindings are installed.
In Ubuntu you would need to:

sudo apt-get install gpsd python-gps
sudo dpkg-reconfigure gpsd
sudo apt-get install python-plasma python-dev

After those are installed, you can proceed to install the plasmoid with plasmapkg -i.

Problems and TODOs

This is all rather dirty and bloated. The correct way to do it would probably be to write a data engine for plasma, which would provide the positional data. Maybe someone will do it, especially if Marble will one day be able to support overlays integrate GeoClue or something similar.

Right now the data travels from the GPS device to the PC in the form of NMEA sentences, gets then converted into gpsd’s own format, python-gps connects to gpsd over TCP port 2947, interprets the gpsd output, hands it over to the applet, which reformats the data yet again. For something so useless that just wastes too many CPU cycles. Interpreting GPS data entirely in python is not hard, but still a bit harder than with gpsd, especially if one wants to cover a lot of GPS devices. Don’t get me wrong, gpsd does its job quite well, it is just a bit overkill for this task.

Another improvement would be readable coordinates. Something like “10 km northwest of Zürich” or even “200 meters south of Sternen Oerlikon, Zürich” would really be much more useful.

Update February 2010: Version 0.16 now uses KDE’s geolocation data engine. This drops the (direct) dependency on gpsd, and allows for ip-based location – unfortunately i now can no longer get my gps to work with it, hoping for kubuntu lucid.

gps-plasmoid_0.16.plasmoid

gps-plasmoid_0.15.plasmoid

Usage

• Start the Program, add a parameter for the port your nmea device is attached to (/dev/ttyUSB0 is the default
• Start google earth or something, load the generated kml file (/tmp/posdate by default)
• Exit the program by pressing ctrl-c, track data will be written to /tmp/track-some time.gpx

Guess I should code something with extra geek value now.
It might be comfortable to have google earth automatically reload the file, so instead open sth. like

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<?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()

readgps.py