GeoClue is a software framework that provides location information to applications from various sources like GPS, WiFi networks, and cell towers. It utilizes D-Bus to share location data between components and can geocode addresses to coordinates and reverse geocode coordinates to addresses. GeoClue has a number of provider components that determine location using different methods, and a master provider that chooses the best provider based on requirements. Applications can access location information through simple interfaces without needing to know the underlying provider.

1. 1
GeoClue
- The Geolocation Service
William.L
wiliwe@gmail.com
2010-06-15

2. 2
Outline
History
Overview
Dependencies
Components
Reference

3. 3
History & Goal
Started during GNOME Summit 2006 in Boston.
Provides a convenient way to find out where the user is,
from a number of sources such as GPS, GSM cell, wifi
network, internetwork.

4. 4
Overview
GeoClue
A software framework utilizing the D-Bus inter-process
communication(IPC) mechanism to provide location
information, and applications can use it to become geo-aware
Can geocode(getting a Position(longitude/latitude
coordinate) from an Address) and
reverse-geocode (getting an Address from a Position)
Licensed under the GNU LGPL
http://geoclue.freedesktop.org/

5. 5
Dependencies (1/2)
GObject
Glib
D-Bus
GPSD
A GPS daemon on most Debian like system
http://gpsd.berlios.de/
Gypsy
Written by Iain Holmes at o-hand
A GPS multiplexing daemon which allows multiple clients
to access GPS data from multiple GPS sources
concurrently
http://gypsy.freedesktop.org/wiki/

6. 6
Dependencies (2/2)
Wammu
A program to manage data in your cell phone such as
contacts, calendar or messages.
http://wammu.eu/
OpenCellID (basement station ID)
Aiming to create a complete database of CellID
worlwide, with their locations.
http://opencellid.org/

7. 7
Components (1/10)
A set of geoinformation interfaces
For querying "current situation“
Position
Address
Velocity
Use a method / signal architecture
Ex : To get current position, use –
geoclue_position_get_position() method or "position-
changed" signal with a callback function

8. 8
Components (2/10)
Class of Interfaces
Position - GeocluePosition
Via gpsd, gypsy, hostip, plazes, gsmloc
Address - GeoclueAddress
Via hostip, plazes, manual, localnet
Velocity - GeoclueVelocity
Via gpsd, gypsy
Geocode - GeoclueGeocode
Via nominatim (http://nominatim.openstreetmap.org/),
geonames (http://www.geonames.org/),
yahoo (http://developer.yahoo.com/maps/rest/V1/geocode.html)
ReverseGeocode - GeoclueReverseGeocode
Via nominatim, geonames
Accuracy - GeoclueAccuracy
Reports the horizontal and vertical accuracy levels

9. 9
Components (3/10)
Provider
Implement more than one Geoclue interface
All Geoclue providers are D-Bus services
Do not have to run as daemons, as D-Bus will start them
when needed (providers may also shut down when they're no
longer used).
Currently has 9 providers -
http://www.freedesktop.org/wiki/Software/GeoClue/Providers

10. 10
Components (4/10)
Type of Providers
User-specified address that maps to a
router's mac address (home, office).
A user-specified address
A web service that gets location based on
your current router mac address.
Interfaces with a user's Plazes account.
http://plazes.com
A web service that guesses location based
on the current IP address.
http://www.hostip.info
Description
Address
Address
Position, Address
Position, Address
Service
Localnet
Manual
Plazes
Hostip
Type

11. 11
Components (5/10)
Type of Providers
Gets cell ID data, and estimates location
from a web service based upon that data
PositionGsmloc
A GPS daemon that supports bluetooth
and serial GPS devices
Position, VelocityGypsy
A web service that can convert an address
to a position. Conversely, it can also find
the nearest address to a given position.
A web service that converts an address to
a position
A GPS daemon that uses TCP sockets
Description
Geocode,
ReverseGeocode
Geocode
Position, Velocity
Service
Geonames
Yahoo
GPSd
Type

12. 12
Components (6/10)
Problem on using Providers
A single provider cannot be the best solution to all problems
The "best" providers will be different depending on the user
Master Provider
Single window for user to use providers
It is an attempt to take away all of the complications of choosing
the right provider
Choose the best provider to provide what you are looking
for based on client requirements and provider availability,
accuracy and resource requirements.
The provider that is actually used may change over time
as conditions change, but the client can just ignore this

13. 13
Components (7/10)
Usage of Master Provider
A typical Master provider use :
Getting a client-specific GeoclueMasterClient from GeoclueMaster
Setting GeoclueMasterClient requirements (such as accuracy)
Starting the wanted interfaces (such as Position)
Using the client just like a regular provider
Master provider is fairly new and may not be as stable
as the rest of Geoclue

14. 14
Components (8/10)
Ex : Master Provider
#include <geoclue/geoclue-master.h>
static void position_changed(...) {
if (fields & GEOCLUE_POSITION_FIELDS_LATITUDE && fields & GEOCLUE_POSITION_FIELDS_LONGITUDE) {
g_print ("t%f, %fnn", latitude, longitude);}
else { g_print ("tLatitude and longitude not available.nn"); } }
int main ()
{
GMainLoop *loop;
GeoclueMaster *master;
GeoclueMasterClient *client;
GeocluePosition *pos;
GeocluePositionFields fields;
double lat, lon;
GError *error = NULL;
g_type_init ();
/ * create a MasterClient using Master * /
master = geoclue_master_get_default ();
client = geoclue_master_create_client (master, NULL, &error);
g_object_unref (master);
if (!client)
{
g_printerr ("Error creating GeoclueMasterClient");
g_error_free (error);
return 1;
}

15. 15
Components (9/10)
/ * Set our requirements: We want at least city level accuracy, require signals,
and allow the use of network (but not e.g. GPS) * /
if (!geoclue_master_client_set_requirements (client, GEOCLUE_ACCURACY_LEVEL_LOCALITY,
0, TRUE, GEOCLUE_RESOURCE_NETWORK, &error))
{
g_printerr ("set_requirements failed: %s", error->message);
g_error_free (error);
g_object_unref (client);
return 1;
}
/ * Get a Position object * /
pos = geoclue_master_client_create_position (client, NULL);
if (!pos) {
g_printerr ("Failed to get a position object");
g_object_unref (client);
return 1;
}
/ * call get_position. We do not know which provider actually provides the answer (although we could find out using MasterClient API) * /
fields = geoclue_position_get_position (pos, NULL, &lat, &lon, NULL, NULL, &error);
if (error) {
g_printerr ("Error in geoclue_position_get_position: %s.n", error->message);
g_error_free (error);
error = NULL;
} else {
if (fields & GEOCLUE_POSITION_FIELDS_LATITUDE &&
fields & GEOCLUE_POSITION_FIELDS_LONGITUDE) {
g_print ("We're at %.3f, %.3f.n", lat, lon); }
}
g_signal_connect (G_OBJECT (pos), "position-changed", G_CALLBACK (position_changed), NULL);

16. 16
Components (10/10)
loop = g_main_loop_new (NULL, FALSE);
g_main_loop_run (loop);
g_main_loop_unref (loop);
g_object_unref (pos);
g_object_unref (client);
return 0;
}

17. 17
References
GeoClue API
http://folks.o-hand.com/jku/geoclue-docs
Geoclue: Location Information Retrieval for Moblin
2.0 Linux
http://software.intel.com/en-us/articles/geoclue-location-
information- retrieval-for-moblin-20-linux/
http://software.intel.com/zh-cn/blogs/2009/03/11/moblin-sdk-
geoclue/