DOI: 10.21227/t8pc-rq85
title: CRAWDAD mannheim/compass 

description: COMPASS is a positioning system based on 802.11 and digital compasses. We apply an two-stage fingerprinting approach: In the training phase, we sample the signal strength of neighboring access points for selected orientations at each reference point and store the data in a database. During the positioning phase, the orientation of the user is utilized to preselect a subset of the training data and based on this data compute her position.last modified :2008-04-16release date :2008-04-11date/time of measurement start :2006-02-11date/time of measurement end :2006-10-14collection environment :Positioning systems are one of the key elements required by
location-based services. We design and implement a positioning system 
called COMPASS which is based on 802.11-compliant network infrastructure 
and digital compasses. On the mobile device, COMPASS samples the signal 
strength values of different access points in its communication range 
and utilizes the orientation of the user to preselect a subset of 
the training data. The remaining training data is used by a probabilistic 
positioning algorithm to determine the position of the user.

While prior systems show limited accuracy due to blocking effects
caused by the human body, we apply digital compasses to detect
the orientations of the users so that they can deal with these blocking
effects. After a short period of training the COMPASS system achieves 
an average error distance of less than 1.65 meters in the experimental 
environment of 312 square meters.network configuration :The test environment is equipped with five Linksys / Cisco WRT54GS and 
four Lancom L-54g access points. All access points support 802.11b and 
802.11g. One Lancom and all Linksys access points are located on the same 
floor as our testing area whereas three Lancom access point are located 
in other places inside the building. The exact position of the access points 
located inside the testing area is marked by squares in the floor plan 
(see the download link below).data collection methodology :We deployed our positioning system in the hallway of an office
building on the campus of the University of Mannheim. The operation
area is nearly 15 meters in width and 36 meters in length,
covering an area of approximately 312 square meters. The floor
plan of the testing area is shown in the floor plan figure 
(see the download link below).  The large hallway in the left part of 
the map is connected by two narrow hallways that are separated by rooms 
such as archives and a kitchen.

We marked the floor plan (see the download link below) with markers 
depicting the grid of the reference points (light-colored dots) and 
the online measurement points (dark dots). The access points are 
marked by squares.

As a client, we used a Lucent Orinco Silver PCMCIA network
card supporting 802.11b. We collected the signal strength samples
on an IBMThinkpad R51 running Linux kernel 2.6.13 and Wireless
Tools 28pre.

To obtain the orientation of the user we used the Silicon Laboratories
C8051F350 Digital Compass Reference Design Board. This device provides 
a USB-to-Serial bridge to access the data and is powered by the USB 
electricity supply. We calibrated the compass in the middle of the operation 
area. In a closer area around the calibration point we measured a variation of 
1 degree. However, variations up to 23 degree were rarely detected at a few 
points of the testing area. These measurement errors occured always close 
to electromagnetic objects such as high-voltage power lines and electronic devices.Tracesetmannheim/compass/signalstrengthA traceset of signal strength collected from 802.11 APs for the COMPASS positioning system.files: offline.tar.gz, online.tar.gzdescription: A traceset of signal strength collected from 802.11 APs for the location estimation used by the COMPASS positioning system.measurement purpose: Location-aware Computing, Positioning Systemsmethodology: The grid of reference points applied to the operation area includes 166 points with a spacing of 1 meter (see the light-colored dots in the floorplan figure). During the offline phase, the signal strength was measured at reference points for different orientations. We then randomly selected 60 coordinates and orientations for the online phase.last modified: 2006-11-14dataname: mannheim/compass/signalstrengthversion: 20060913change: the initial versionrelease date: 2006-09-13date/time of measurement start: 2006-02-11date/time of measurement end: 2006-03-09mannheim/compass/signalstrength Tracesoffline: A trace of signal strength values from 802.11 APs measured at reference points for different orientations.configuration: During the offline phase, the signal strength was measured at reference points for different orientations. We collected 110 signal strength measurements at each reference point and for each orientation. This leads to 146,080 measurements for the offline phase. We spent over 10 hours to collect all the data.format: t="Timestamp"; id="MACofScanDevice"; pos="RealPosition"; degree="orientation"; "MACofResponse1"="SignalStrengthValue","Frequency","Mode"; ... "MACofResponseN"="SignalStrengthValue","Frequency","Mode" t: timestamp in milliseconds since midnight, January 1, 1970 UTC id: MAC address of the scanning device pos: the physical coordinate of the scanning device degree: orientation of the user carrying the scanning device in degrees 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 and its mode (access point = 3, device in adhoc mode = 1)description: A trace of signal strength values from 802.11 APs measured at reference points for different orientations for the offline phase of the COMPASS positioning system.last modified: 2006-11-14dataname: mannheim/compass/signalstrength/offlineversion: 20060913change: the initial versionrelease date: 2006-09-13date/time of measurement start: 2006-02-11date/time of measurement end: 2006-03-09url: /download/mannheim/compass/offline.tar.gzonline: A trace of signal strength, which is derived from mannheim/compass/signalstrength/offline.configuration: We randomly selected 60 coordinates and orientations for the online phase. The only condition to select a point inside the testing area as an online set point is that it is surrounded by four reference points. Again, we collected 110 signal strength measurements for each online set point, leading to 6,600 measurements in total.format: t="Timestamp"; id="MACofScanDevice"; pos="RealPosition"; degree="orientation"; "MACofResponse1"="SignalStrengthValue","Frequency","Mode"; ... "MACofResponseN"="SignalStrengthValue","Frequency","Mode" t: timestamp in milliseconds since midnight, January 1, 1970 UTC id: MAC address of the scanning device pos: the physical coordinate of the scanning device degree: orientation of the user carrying the scanning device in degrees 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 and its mode (access point = 3, device in adhoc mode = 1)description: A trace of signal strength, which is derived from mannheim/compass/signalstrength/offline for online phase of the COMPASS positioning system.last modified: 2006-11-14dataname: mannheim/compass/signalstrength/onlineversion: 20060913change: the initial versionrelease date: 2006-09-29date/time of measurement start: 2006-02-11date/time of measurement end: 2006-03-09url: /download/mannheim/compass/online.tar.gzmannheim/compass/802.11A traceset of signal strength collected from 802.11 APs for the COMPASS positioning system.description: A traceset of signal strength collected from 802.11 APs for the location estimation used by the COMPASS positioning system.measurement purpose: Location-aware Computing, Positioning Systemsmethodology: 1. Local Test Environment We deployed the positioning system on the second floor of an office building on the campus of the University of Mannheim. The operation area is nearly 15 meters in width and 36 meters in length, covering an area of approximately 312 square meters. The floor plan of the operation area is shown in [Figure: floor plan for mannheim/compass/802.11]. The large hallway in the left part of the map is connected by two narrow hallways that are separated by rooms such as a copier room, an archive and a kitchen. The rooms depicted on both sides of the narrow hallways are mainly used as offices, and due to access restrictions they could not be included into the operation area. 2. Hardware and Software Setup Initially, the test environment was covered by one Linksys / Cisco WRT54GS and two enterasys RBT-4102-EU access points administered by the computer center of our university. We additionally installed 11 access points: Two D-Link DWL-G700AP, three NETGEAR WG102, and six Linksys / Cisco WRT54G access points. All access points support 802.11b and 802.11g. Except of one enterasys access point, all access points are located on the same floor as our operation area. This particular enterasys access point is placed on a lower floor, however, it covers the operation area completely. The position of this access point is marked by an orange ring and the positions of the other access points are marked by orange circles (see [Figure: floor plan for mannheim/compass/802.11]). As a client, we used a Lucent Orinoco Silver PCMCIA network card supporting 802.11b. This card was plugged into an IBM Thinkpad R51 running Linux kernel 2.6.13 and Wireless Tools 28pre. To collect signal strength samples, we implemented a framework that contains two parts: A library that cooperates with the network card driver to perform scans and capture internal driver information, and an easy-to-use application that stores these information in a file together with additional data such as the physical position and a timestamp. Further, the application configures the library to select a scan frequency and scan technique for the signal strength measurements. For our experiments we used active scanning. Active scanning is defined in the 802.11 standard1 and it is a technique to find a suitable gateway to the Internet by measuring the signal strength of access points within communication range. From the driver our library collects the following information for each device that replies to an active scan: - MAC address of the device - received signal strength - noise level - mode of the device (i.e. access point or ad-hoc) - frequency used for the communication Although only the MAC address, mode and received signal strength values are required by 802.11-based positioning systems, we stored the additional information for further analysis and debugging purposes.last modified: 2008-05-15dataname: mannheim/compass/802.11version: 20080411change: the initial versionrelease date: 2008-04-11date/time of measurement start: 2006-10-14date/time of measurement end: 2006-10-14mannheim/compass/802.11 Tracesoffline: A trace of signal strength values from 802.11 APs measured at reference points for different orientations.configuration: The grid of reference points applied to the operation area includes 612 points with a spacing of 0.5 meter (see the blue markers in [Figure: floor plan for mannheim/compass/802.11]). During the offline phase, we collected 110 signal strength samples at each reference point, resulting in 72,600 samples in total. We spent over ten hours to collect all the data, however, we want to point out that for a productive deployment of a positioning system 20 signal strength samples and a grid with grid spacing of 1.5 meters will be sufficient, cutting down the expenditure of time to less than half an hour.format: t="Timestamp"; id="MACofScanDevice"; pos="RealPosition"; degree="orientation"; "MACofResponse1"="SignalStrengthValue","Frequency","Mode"; ... "MACofResponseN"="SignalStrengthValue","Frequency","Mode" t: timestamp in milliseconds since midnight, January 1, 1970 UTC id: MAC address of the scanning device pos: the physical coordinate of the scanning device degree: orientation of the user carrying the scanning device in degrees 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 and its mode (access point = 3, device in adhoc mode = 1)description: A trace of signal strength values from 802.11 APs measured at reference points for different orientations for the offline phase of the COMPASS positioning system.last modified: 2008-05-15dataname: mannheim/compass/802.11/offlineversion: 20080411release date: 2008-04-11date/time of measurement start: 2006-10-14date/time of measurement end: 2006-10-14online: A trace of signal strength, which is derived from mannheim/compass/802.11/offline.configuration: For the online phase, we randomly selected 83 coordinates. The only condition to select a point inside the operation area as a online point is that it is surrounded by four reference points of the grid. Again, we collected 110 signal strength samples for each online point, leading to 9,460 samples in total. In [Figure: floor plan for mannheim/compass/802.11] the online points are marked by purple dots.format: t="Timestamp"; id="MACofScanDevice"; pos="RealPosition"; degree="orientation"; "MACofResponse1"="SignalStrengthValue","Frequency","Mode"; ... "MACofResponseN"="SignalStrengthValue","Frequency","Mode" t: timestamp in milliseconds since midnight, January 1, 1970 UTC id: MAC address of the scanning device pos: the physical coordinate of the scanning device degree: orientation of the user carrying the scanning device in degrees 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 and its mode (access point = 3, device in adhoc mode = 1)description: A trace of signal strength, which is derived from mannheim/compass/802.11/offline for online phase of the COMPASS positioning system.last modified: 2008-05-15dataname: mannheim/compass/802.11/onlineversion: 20080411change: the initial versionrelease date: 2008-04-11date/time of measurement start: 2006-10-14date/time of measurement end: 2006-10-14mannheim/compass/fingerprintA traceset of signal strength collected from 802.11 APs for the COMPASS positioning systemdescription: A traceset of signal strength collected from 802.11 APs for the location estimation used by the COMPASS positioning system.measurement purpose: Location-aware Computing, Positioning Systemsmethodology: 1. Local Test Environment We deployed our 802.11-based positioning system on the second floor of our office building on the campus of the University of Mannheim. The operation area is nearly 57 meters in width and 32 meters in length; approximately 221 square meters are covered. The floor plan of the operation area is shown in [Figure: floor plan for mannheim/compass/fingerprint]. 2. Hardware and Software Setup Initially, the test environment was covered by twelve access points. Seven of them are administered by the computer center of our university. The other five are installed in nearby buildings and offices. We additionally installed thirteen access points. Our data show that most of the access points cover only parts of the operation area. In fact, only two access points cover the operation area completely. One of these access points is the one marked in the middle of the storage room in the horizontal hallway in the right part of the building. This access point is located in a suspended ceiling on top of this room. The position of the second access point is in an office one floor below our operation area. The positions of the access points that are located on the same floor and inside the same building parts as our operation area are marked by orange circles in [Figure: floor plan for mannheim/compass/fingerprint]. As a client, we used a Lucent Orinoco Silver PCMCIA network card supporting 802.11b. This card was plugged into an IBM Thinkpad R51 running Linux kernel 2.6.13 and Wireless Tools 28pre. To collect signal strength samples, we implemented our own set of tools called "Loc{lib,trace,eva,ana}".last modified: 2008-05-15dataname: mannheim/compass/fingerprintversion: 20080411change: the initial versionrelease date: 2008-04-11date/time of measurement start: 2006-08-24date/time of measurement end: 2006-08-24mannheim/compass/fingerprint Tracesoffline: A trace of signal strength values from 802.11 APs measured at reference points for different orientations.configuration: The grid of reference spots in the operation area includes 130 spots with a spacing of 1.5 meters (see the blue marks in [Figure: floor plan for mannheim/compass/fingerprint]). During the training phase, we collected 110 signal strength samples at each reference spot.format: t="Timestamp"; id="MACofScanDevice"; pos="RealPosition"; degree="orientation"; "MACofResponse1"="SignalStrengthValue","Frequency","Mode"; ... "MACofResponseN"="SignalStrengthValue","Frequency","Mode" t: timestamp in milliseconds since midnight, January 1, 1970 UTC id: MAC address of the scanning device pos: the physical coordinate of the scanning device degree: orientation of the user carrying the scanning device in degrees 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 and its mode (access point = 3, device in adhoc mode = 1)description: A trace of signal strength values from 802.11 APs measured at reference points for different orientations for the offline phase of the COMPASS positioning system.last modified: 2008-05-15dataname: mannheim/compass/fingerprint/offlineversion: 20080411change: the initial versionrelease date: 2008-04-11date/time of measurement start: 2006-08-24date/time of measurement end: 2006-08-24online: A trace of signal strength, which is derived from mannheim/compass/fingerprint/offline.configuration: For the position determination phase, we randomly selected 46 spots. Again, we collected 110 signal strength samples for each positioning spot. In [Figure: floor plan for mannheim/compass/fingerprint], the positioning spots are marked by purple dots. We spent more than ten hours to collect all the data.format: t="Timestamp"; id="MACofScanDevice"; pos="RealPosition"; degree="orientation"; "MACofResponse1"="SignalStrengthValue","Frequency","Mode"; ... "MACofResponseN"="SignalStrengthValue","Frequency","Mode" t: timestamp in milliseconds since midnight, January 1, 1970 UTC id: MAC address of the scanning device pos: the physical coordinate of the scanning device degree: orientation of the user carrying the scanning device in degrees 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 and its mode (access point = 3, device in adhoc mode = 1)description: A trace of signal strength, which is derived from mannheim/compass/fingerprint/offline for online phase of the COMPASS positioning system.last modified: 2008-05-15dataname: mannheim/compass/fingerprint/onlineversion: 20080411change: the initial versionrelease date: 2008-04-11date/time of measurement start: 2006-08-24date/time of measurement end: 2006-08-24