This page lists both onsite and offsite resources for programmers
trying to understand GPS technology.
In the descriptions below, the adjective "evil" applied to the
distribution terms of a standard or technical specification means that
(a) it is not available for free download, and (b) it cannot legally
be redistributed. The phrase "extremely evil" means that not only are
the distribution terms evil, but that attack lawyers for the document
publisher have been known to threaten people who quote it on the
Web.
This was a selection of the files available at GPSD's Google Code
document repository. Those are looking for a new home.
GPS standards
- NMEA 0183
- This is the official standard from the National Maritime
Electronics Association describing how GPSes are supposed to
report to computers over a serial or USB link. The distribution terms
are extremely evil. Consequently, nobody on the GPSD project has ever
looked at it.
- NMEA sentences
- Because the NMEA 0183 standard itself is extremely evil, the GPSD
project has collated comprehensive information on the prescriptions of
that standard from various Web resources written by people who have
read it and/or studied the behavior of GPSes claiming to conform to
it. This is the result.
- NMEA data
- This is one of the sources for the above. Includes some
information on vendor-specific quirks that we don't.
- Navstar
Global Positioning Interface Specification IS-GPS-200J (2018)
- This is the official specification for interpreting radio
transmission from GPS satellites. You do not need to read this
unless you are trying to make sense of the raw 50BPS subframe
data. Be warned: though this specification is not evil, it
is complex and nasty.
- Standard Positioning Service
Performance Specification (2008)
- This document defines the levels of performance the U.S. Government makes
available to civil users through the GPS Standard Positioning Service
(SPS).
- World Geodetic System
- Technical and historical summary of WGS84.
- WAAS System Specification
- This is the official specification for the FAA's Wide Area
Augmentation System.
- RTCM
Recommended Standards for Differential GNSS
- This is the ordering page for the official RTCM SC-104 standards,
both the obsolescent 2.x and current 3.x versions. The distribution
terms are evil. At least one of the GPSD project members has purchased
official copies, so we do have full details of the message format.
Copies of some of these have leaked onto the Web and may be found by
searching for "RTCM
10402.3" or "RTCM
10403.1".
- ITU-R M.823-2
- This specification documents some of the murky depths of
rtcm-104, the specification used for broadcasting differential-gps
corrections. Unfortunately, its distribution terms are also evil.
- Galileo Open Service SIS
ICD (2010)
- This is issue 1 revision 1 0 of the Galileo Open Service Signal In Space
Interface Control Document. The latest version of the official
standard found here.
- Ntrip home page
- NTRIP is a protocol for shipping DGPS corrections that uses HTTP
as a transport layer. The distribution terms for the NTRIP standard
are evil, but a stripped down version of the document is freely
available on the home page. Version 1.0 of the standard is poorly
written, confusing and leaves too much open to the interpretation of
the implementor. With the help of examples in the official standard
(missing in the online version) and the C and Perl reference
implementations, it is however possible to develop a working Ntrip
client.
- AIVDM/AIVDO protocol decoding
- This document describes AIVDM, a standard layered on top of NMEA
0183 and used for the marine Automatic Identification System (AIS).
The core AIVDM standard is no longer evil (see below), but complete
information on AIS and its addenda remains otherwise difficult to
collect from scattered and rather impenetrable standards
documents.
- M.1371
: Technical characteristics for an automatic identification system
using time-division multiple access in the VHF maritime mobile band
- The official standard descrcribing AIS.
- GPX Exchange Format
- GPX (the GPS Exchange Format) is a light-weight
XML data format for the interchange of GPS data (waypoints, routes,
and tracks) between applications and Web services on the Internet. The
GPSD suite includes a client,
gpxlogger, that makes logs
in this format.
GPS operation
- NAVSTAR
Global Positioning and Surveying
- US Army Corps of Engineers, Engineer Manual 1110-1-1003 "provides
technical specifications and procedural guidance for surveying and
mapping with the NAVSTAR Global Positioning System (GPS). ... Procedural
and quality control standards are defined to establish... uniformity
in the use of GPS..." This document offers significant insight into
error modelling; anyone who dares to ask "so how accurate is my GPS?"
should be gently encouraged to study it.
- Worldwide Beacon DGPS Status
- This paper dates from 1999 and some of the information in it is therefore
probably out of date. Nevertheless, it's the best public documentation on the
history and architecture of the worldwide DGPS beacon system we've found.
- Inside
assisted GPS: helping GPS help you
- Good article on techniques for cutting GPS startup latency and
increasing precision, mostly focused on assistance via cellphone networks.
- Worldwide list of NTRIP
Casters
- Master list of sites that provide RTCM correction info over the
Internet.
Vendor protocols
Due to the inadequacies of NMEA, GPS chipset vendors have invented
NMEA extensions or their own more tightly-designed reporting formats.
This is a collection of descriptions of them. Many of these have
already been used in the implementation of gpsd; others
may be used in the future.
If you have access to a GPS vendor manual we don't already carry,
please send it to us. If it's live on the web, mailing the URL will
be sufficient. The names in this SHA1 checksums
file should be a good clue which ones we already have.
Good manuals generate customer interest and loyalty. Judging by the
legal notices in them, either (a) many GPS vendors are run by people
who think that making their documentation hard to get and illegal to
redistribute doesn't damage their sales prospects, or (b) many GPS
vendors unthinkingly slap in a boilerplate notice that makes them look
like they are run by the aforementioned sort of idiot. We are blithely
ignoring all this nonsense here. If you are a GPS vendor
representative, be advised that if you so request, we will (a) remove
your manuals, and then (b) laugh at and publicly mock you
for having been so stupid as to demand this.
SiRF and SiRF variants
- SiRF
Binary Protocol Reference Manual (2.4, November 2008)
- The
binary protocol for the chip used by over 80% of consumer-grade GPS
mice. For comparison we also have older versions:
2.2
(December 2007),
1.7
(October 2005) and 1.6
(April 2005) .
- SiRF
NMEA Protocol Reference Manual (2.2, November 2008)
- SiRF
NMEA Protocol Reference Manual (2.1, December 2007)
- SiRF GPS Protocol
Reference Manual (revision 1.30, undated)
- This what SiRF gives OEMs as a reference for SiRF's NMEA 0183
extensions. Notably, it describes the commands for switching to SiRF
binary mode.
- TIM GPS
Receiver Macro-Component (offsite link) (version E1, April 2003)
- Describes the SiRFstarII chipset used by u-blox and some others.
gpsd supports it. While obsolete, this file documents certain
aspects of the protocol that SiRF has removed from current versions of the
protocol documentation.
- u-blox extension to SiRF binary protocol (March 2002)
- u-blox was an OEM-enhanced firmware variant of the SiRF-1 chip.
gpsd supports it. It's been rendered obsolete by the SiRF 2
and 3 chips.
- u-blox M8 Rev 08 (December 2014)
- he u-blox M8 support GPS, GLONASS and BeiDou.
gpsd supports it.
Fastrax
- NMEA Protocol
Specification for iTrax02 Evaluation Kit (Rev 1.11, June
2003)
- Describes the NMEA extensions for the iTrax chipset
used by Fastrax GPSes. Supported by
gpsd.
- iTALK protocol specification
(Rev 1.5, March 2002)
- Describes the binary protocol for the iTrax chipset used by
Fastrax GPSes. This documents version 2; version 3, which is not
actually backward compatible, is documented at the iSuite developer
website, iTrax2 is not supported by
gpsd, iTrax3 is
somewhat functional.
Garmin
-
GPS 16/17 Series Technical Specification (offsite link) (Revision
C, October 2005)
- Describes the extended NMEA, with GARMIN
proprietary sentences PGRMB, PGRME, PGRMF, PGRMM, PGRMT, and PGRMV
(and optional GPALM sentence), emitted by the Garmin GPS16 and 17. For
programming purposes, effectively identical to their earlier reference
on the Garmin 15H and 15L.
- Garmin Simple
Text Protocol
- Some digital cameras are alleged to use
this very simple textual report format.
Novatel
- Novatel Superstar II User Manual (2005)
- Describes the OEM board, include some good general overview
material on GPS technology. Doesn't describe control or reporting
commands.
San Jose Navigation
- FV25 user manual (January 2005)
- Describes UBX binary protocol and NMEA extensions supported by the
San Jose Navigation FV-25 (u-blox ANTARIS) GPS chipset. UBX is now supported
by
gpsd.
Other Current GPSes
- CXD2951 Communication Command Specification (Version 1.7, 2004)
- Describes the extension command set supported by the Sony GPS
CXD2951 chipset. Supported by
gpsd.
- Holux GM-210 GPS Receiver User's
Guide (May 2003)
- Describes NMEA as emitted by the Holux GM210. This is a very
generic NMEA GPS. Supported by
gpsd.
- GM-X205 GPS Receiver Module User's Guide (Issue D, August 2003)
- Describes the binary protocol emitted
by EverMore GM-X205 GPS chipset. Supported by
gpsd.
- Crescent Integrator's Manual (November 2005)
- Reference for the Hemisphere GPS from CSI Wireless. Has both an NMEA mode
and a binary protocol. We have not been able to test with one of these, but the
manual suggests
gpsd should handle the NMEA mode just fine.
- Thales A12/B12/C12 Reference Manual (Revision D, 2005)
- Reference for a line of Thales GPS modules apparently designed
for embedded vehicle and cargo tracking. Uses a very extended dialect
of NMEA they call the
standard Ashtech command set
. We
have not been able to test with one of these, but the manual suggests
gpsd should handle the NMEA mode just fine.
- True North Revolution Compass Technical
Reference (Revision B, August 2003)
- Interface spec for a digital magnetic compass that reports in NMEA.
gpsd had support for this in versions up to 2.33; whether it keeps
that status in later releases will depend on whether we can get test hardware.
- WD-G-ZX4120 User's Manual (Version 1.0)
- This file documents a module based on NemeriX chips, and the
NMEA extensions used.
gpsd should just work in NMEA mode.
- EB-230 User's Manual (Version 1.2)
- This file documents one elusive Mediatek GPS module, and the proprietary
NMEA extensions used.
gpsd should just work in NMEA mode.
- Mediatek Packet User's Manual (Version 0.7)
- This file documents the proprietary Mediatek NMEA-ish protocol.
gpsd should just work in NMEA mode.
- LocSense Binary Message Protocol (Version 1.5)
- This file documents the LocSense binary message protocol. This protocol
is currently unsupported.
gpsd should just work in NMEA mode
with LocSense based receivers.
- Navcom Technical Reference Manual (rev. K, Aug 2008)
- Technical reference and protocol specifications for Navcom receivers.
Obsolete products
- Zodiac Serial Data Interface Specification (Revision 11, September 1996)
- Describes the binary protocol used by Rockwell/Conexant Zodiac chipsets.
Supported by
gpsd. Now obsolete; SiRF ate their lunch.
- Axiom Sandpiper II Documentation [broken link] (August 2000)
- We have archived the most complete available documentation on the Axiom
Sandpiper II OEM module (discontinued, vendor has gone out of
business). Supported by
gpsd.
Other
- ECEF-to-Geodetic C Code
- Sample C code for conversion from the Earth Centered-Earth Fixed
coordinates reported by many vendor binary protocols to ordinary
geodetic coordinates.
- Aviation
Formulary
- Compendium of formulas related to geodetic navigation, with examples.
