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Development of the low-cost RTK-GPS receiver with an open source program
package RTKLIB
Tomoji Takasu 1, and Akio Yasuda 2
Laboratory of Satellite Navigation, Tokyo University of Marine Science and Technology
1

(Tel: +81-5245-7365, E-mail: ttaka@gpspp.sakura.ne.jp)
2

(Tel: +81-5245-7365, E-mail: yasuda@kaiyodai.ac.jp)

Abstract: RTKLIB is an open source program package for RTK-GPS developed by the authors. RTKLIB is a
compact and portable program library written in C to provide a standard platform for RTK-GPS
applications. The library implements fundamental navigation functions and carrier-based relative
positioning algorithms for RTK-GPS with integer ambiguity resolution by LAMBDA. RTKLIB also
supports data communication via serial I/O, TCP/IP connection and NTRIP, and various data formats
including RTCM 2.3, RTCM 3.1 and proprietary raw messages for some GPS receivers. By supporting
RTCM and NTRIP, NRTK (Network RTK) service can be used with RTKLIB. From the version 2.2.0,
RTKLIB has been distributed under the GPLv3 license. RTKLIB was originally implemented on
Windows PC. In this study, we port RTKLIB to a small and compact single-board computer BeagleBoard
and construct a low-cost RTK-GPS receiver with RTKLIB. BeagleBoard has 600MHz ARM Cotex-A8
core CPU and supports embedded Linux environment. In order to acquire and track GPS signals, we
employ a single-frequency GPS receiver module LEA-4T provided by u-blox AG. The RTK-GPS server
running on BeagleBoard inputs the u-blox raw binary data messages. The server also inputs the
base-station data via a serial port or USB network device and computes RTK-GPS solution in real-time.
The total cost of the developed RTK-GPS receiver was about $400. To demonstrate and verify the
performance of the low-cost RTK-GPS receiver, we made some field tests. In these tests, CPU/memory
usage, accuracy of solutions and fixing ratio are evaluated. According to the test results, even with such a
low-cost RTK-GPS receiver, we can obtain reasonable performance in company with RTKLIB.
Keywords:

RKTLIB, Open Source Software, Low-Cost RTK-GPS Receiver, BeagleBoard

1. Introduction
RTK-GPS (real-time kinematic GPS) is one of the most precise
positioning technologies, with which users can obtain cm-level
accuracy of the position in real-time by processing carrier-phase
measurements of GPS signals. Conventionally RTK-GPS had
been utilized for limited application like geodetic survey. In these
days, the application of RTK-GPS has b...
Development of the low-cost RTK-GPS receiver with an open source program
package RTKLIB
Tomoji Takasu
1
, and Akio Yasuda
2
Laboratory of Satellite Navigation, Tokyo University of Marine Science and Technology
1
(Tel: +81-5245-7365, E-mail: ttaka@gpspp.sakura.ne.jp)
2
(Tel: +81-5245-7365, E-mail: yasuda@kaiyodai.ac.jp)
Abstract: RTKLIB is an open source program package for RTK-GPS developed by the authors. RTKLIB is a
compact and portable program library written in C to provide a standard platform for RTK-GPS
applications. The library implements fundamental navigation functions and carrier-based relative
positioning algorithms for RTK-GPS with integer ambiguity resolution by LAMBDA. RTKLIB also
supports data communication via serial I/O, TCP/IP connection and NTRIP, and various data formats
including RTCM 2.3, RTCM 3.1 and proprietary raw messages for some GPS receivers. By supporting
RTCM and NTRIP, NRTK (Network RTK) service can be used with RTKLIB. From the version 2.2.0,
RTKLIB has been distributed under the GPLv3 license. RTKLIB was originally implemented on
Windows PC. In this study, we port RTKLIB to a small and compact single-board computer BeagleBoard
and construct a low-cost RTK-GPS receiver with RTKLIB. BeagleBoard has 600MHz ARM Cotex-A8
core CPU and supports embedded Linux environment. In order to acquire and track GPS signals, we
employ a single-frequency GPS receiver module LEA-4T provided by u-blox AG. The RTK-GPS server
running on BeagleBoard inputs the u-blox raw binary data messages. The server also inputs the
base-station data via a serial port or USB network device and computes RTK-GPS solution in real-time.
The total cost of the developed RTK-GPS receiver was about $400. To demonstrate and verify the
performance of the low-cost RTK-GPS receiver, we made some field tests. In these tests, CPU/memory
usage, accuracy of solutions and fixing ratio are evaluated. According to the test results, even with such a
low-cost RTK-GPS receiver, we can obtain reasonable performance in company with RTKLIB.
Keywords: RKTLIB, Open Source Software, Low-Cost RTK-GPS Receiver, BeagleBoard
1. Introduction
RTK-GPS (real-time kinematic GPS) is one of the most precise
positioning technologies, with which users can obtain cm-level
accuracy of the position in real-time by processing carrier-phase
measurements of GPS signals. Conventionally RTK-GPS had
been utilized for limited application like geodetic survey. In these
days, the application of RTK-GPS has been continuously
expanded to various areas like mobile mapping system, precise
navigation of vehicles, construction machine control and
precision agriculture. The precise positioning technology with
RTK-GPS is expected to be used for much wider applications
increasingly in the future.
For RTK-GPS, users usually need to prepare geodetic-grade
receivers with the firmware supporting RTK-GPS or the
proprietary RTK-GPS software on the receiver controller or PC
provided by the receiver vendor. The receivers or such software
for RTK-GPS, however, are generally still very expensive
comparing to general-purpose GPS receivers. This is one of the
reasons why RTK-GPS is still not popular and is used only for
limited application areas. Many peoples, who require more
precise position, are longing much lower cost RTK-GPS
receivers.
Since several years ago, the authors have been developing a
compact and portable software RTK-GPS library. We refer the
library RTKLIB, which is simply derived from "RTK library" [1].
Originally RTKLIB was intended to be used for our internal
research work in order to evaluate precise positioning algorithms
or to provide an application platform for development of precise
positioning systems. In the beginning, RTKLIB had very simple
function for carrier-based relative positioning and RINEX [2] file
handling for post processing. In company with several version up,
a lot of useful functions and APs (application programs) for
RTK-GPS were added to RTKLIB. From version 2.2.0 released
in 2009, we have been distributing RTKLIB as an open source
program package under the GPLv3 license [3]. The package of
RTKLIB consists of user executable binary APs on Windows and
whole source programs of the library and the APs. Users can
freely download the program package, use the APs, install or link
the library to user own AP and modify the source codes
according to the requirements for user applications.
The latest version of RTKLIB supports some consumer-grade
receivers which are able to output raw measurement data of GPS
signals. With RTKLIB and such receivers, users can construct
and operate their original low-cost RTK-GPS system. The
authors have already evaluated the RTK-GPS performance with
such consumer-grade single-frequency antennas and receivers by
field tests [4]. Such tests were conducted in order to clarify issues
to apply them to RTK-GPS. As the results of these studies, we
found that the difference between consumer-grade receivers and
geodetic-grade ones is not so large regarding to the receiver
performance itself. With good antennas, we can obtain cm-level
accuracy of the receiver position even with such low-cost
receivers. However, dual-frequency receivers have an advantage
of much shorter time of ambiguity resolution. With a
single-frequency receiver, at least a few minutes are necessary to
obtain the first fixed solution. So, in the environment with many
cycle slips like for mobile vehicle navigation, low-cost receiver is
not suitable for RTK-GPS. Though, for the application with
continuous observation like crustal deformation monitoring,
low-cost single-frequency receiver could be applicable for short
baseline RTK-GPS.
In this study, we develop a RTK-GPS receiver with RTKLIB in
order to demonstrate such a low-cost RTK-GPS system and
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