CRAWDAD tools/collect/location/loctrace

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University of Mannheim, Germany
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Last updated:
Wed, 12/05/2007 - 08:00
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Loctrace - a collection tool for 802.11-based positioning systems.

Loctrace is a research tool for 802.11-based positioning systems. Loctrace gathers data offered by Loclib and stores it in a file.

Lastmodified :


Dataname :


File :

loctrace-0.5.src.tar.gz, loctrace-0.5.tar.gz

Releasedate :


Change :

the initial version.

References :

The Loctrace website

Website :

Keyword :

signal strength

License :

This tool is released under the GNU General Public License.
Please respect our work and abide the license.

Output :

See "usage" for details.

Parameters :

See "usage" for details.

Usage :

To start the tracer just invoke

java -Djava.library.path=PATH_LOCLIB_JNI -cp loctrace-0.5.jar:locutil1-0.5.1.jar:loclib-0.7.5.jar:debug-disable-1.1.jar:hexdump-0.1.jar:libdbus-java-2.3.1.jar:unix-0.2.jar org.pi4.loctrace.wirelesslan.Tracer

Please replace the placeholder PATH_LOCLIB_JNI with the path to the loclib
native library according to your installation.

Example :

The data collected from Loclib is stored in a human-readable trace file
and contains lines that adhere to the following format:


- t: timestamp in milliseconds since midnight, January 1, 1970 UTC
- pos: the physical coordinate of the scanning network device
- id: MAC address of the network device used for scanning
- degree: direction of the user carrying the scanning device in degrees
(only set if a digital compass is available)
- MAC: MAC address of a responding peer (e.g. an access point or a device
in adhoc mode) with the corresponding values for signal strength in dBm,
the channel frequency, its mode (access point = 3, device in adhoc mode = 1)
and noise level in dBm.

Trace files generated by Tracer are a major building block for our overall
research process. These files can be used by Loceva to evaluate and emulate
different positioning algorithms and scenarios. Furthermore, the traces
can be displayed for visual inspection by tools of the Locana package.
Finally, these traces can be used as an offline fingerprint database during
normal operation of an 802.11-based positioning system.

Algorithm :

1. Overview

Loctrace mainly consists of one application. This application gathers
data offered by Loclib and stores it in a file.

2. Tracer

Loctrace contains only one application: Tracer. Tracer is used to collect
the data required to create fingerprint databases. To achieve this goal,
Tracer is build on top of Loclib and directly retrieves sensor-specific data
(e.g., the signal strength of access points within communication range in
an 802.11-based wireless network). It contains a graphical user interface
(GUI) to make the configuration process easy to handle (e.g., select
a scanning mode and the scanning device).

Various parameters such as the number of scans or the delay between
two consecutive scans are also configurable through the GUI. If the trace
process is started, a histogram pops up in the bottom part of Tracer showing
the access points within communication range and their corresponding signal
strength distributions.

The files in this directory are a CRAWDAD toolset hosted by IEEE DataPort. 

About CRAWDAD: the Community Resource for Archiving Wireless Data At Dartmouth is a data resource for the research community interested in wireless networks and mobile computing. 

CRAWDAD was founded at Dartmouth College in 2004, led by Tristan Henderson, David Kotz, and Chris McDonald. CRAWDAD datasets and toolsets are hosted by IEEE DataPort as of November 2022. 

Note: Please use the tools in an ethical and responsible way with the aim of doing no harm to any person or entity for the benefit of society at large. Please respect the privacy of any human subjects whose wireless-network activity is captured by the tools and comply with all applicable laws, including without limitation such applicable laws pertaining to the protection of personal information, security of data, and data breaches. Please do not apply, adapt or develop algorithms for the extraction of the true identity of users and other information of a personal nature, which might constitute personally identifiable information or protected health information under any such applicable laws. Do not publish or otherwise disclose to any other person or entity any information that constitutes personally identifiable information or protected health information under any such applicable laws derived from the tools through manual or automated techniques. 

Please acknowledge the source of the tools in any publications or presentations reporting use of these tools. 


Thomas King, Stephan Kopf, Thomas Butter, Hendrik Lemelson, Thomas Haenselmann, Wolfgang Effelsberg, CRAWDAD toolset tools/collect/location/loctrace (v. 2007‑09‑14), Sep 2007.

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These datasets are part of Community Resource for Archiving Wireless Data (CRAWDAD). CRAWDAD began in 2004 at Dartmouth College as a place to share wireless network data with the research community. Its purpose was to enable access to data from real networks and real mobile users at a time when collecting such data was challenging and expensive. The archive has continued to grow since its inception, and starting in summer 2022 is being housed on IEEE DataPort.

Questions about CRAWDAD? See our CRAWDAD FAQ. Interested in submitting your dataset to the CRAWDAD collection? Get started, by submitting an Open Access Dataset.