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gps_tests.htm
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gps test results added
--- NEW FILE: gps_tests.htm ---
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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<head>
<link type="text/css" rel="stylesheet" href="firebug.css">
<link rel="SHORTCUT ICON" href="./images/favicon.ico">
<title>
GPS Receiver Performance Tests
</title>
</head>
<body>
<h1>
GPS Receiver Performance Tests
</h1>
<p>
A series of tests were conducted to measure the following
</p>
<ol>
<li>
GPS cold-start acquisition time,
</li>
<li>
location accuracy, and
</li>
<li>
movement tracking.
</li>
</ol>
<p>
Tests were performed with hardware that might be used in the
wildlife setting:
</p>
<ul>
<li>
Fujitsu tablet PC
</li>
<li>
Leadtek GPS Receiver and Mica2 host mounted unto a Programming Board
</li>
<li>
GPS Antenna
</ul>
<p>
Location accuracy and movement tracking were determined with the
aid of GeoMapper Universal 1.3 software on the Fujitsu.
</p>
<h2>
Acquisition Time
</h2>
<p>
Several tests were conducted in different locations in order to
determing the time required for the receiver to acquire three
or more GPS satellites. Measurements were done on a clear morning
in a sparsely wooded suburban environment.
</p>
<p>
For raw data, click <a href="cold_start.htm">here</a>. The average
cold-start time from 22 samples taken in various locations was between
51 and 52 seconds. Moreover, the following observations were made:
<ul>
<li>
Cold-start acquisition time seems to be unrelated to the # of
satellites in line of sight.
</li>
<li>
Geographical data more accurate with four or more satellites.
</li>
<li>
As observed at 'Main Stacks' and 'Under Trees', GPS occasionally
fails even if an adequate number of satellites is know to be in
line of sight.
</li>
<li>
Small tree canopies do not block GPS signals.
</li>
<li>
Acquisition times might be reduced by setting the receiver's
sampling rate rather than power cycling it from the host (mote).
To test this, though, it will be necessary to send commands to the
receiver.
</li>
</ul>
<h2>
Location Accuracy
</h2>
<p>
When the number of satellites is greater than three, the GPS
estimatation was reliably within ten meters of the true location.
In this regard, the Leadtek performed similar to other receivers
of the same class.
</p>
<h2>
Movement Tracking
</h2>
<p>
Lastly, a brief experiment was done to determine how well the
receiver could track movement beyond the ten meter error. In
particular, the GeoMapper software was used to see whether the
GPS could follow a walk around Memorial Glade without lag.
(Note: no pauses were taken during walks.)
</p>
<p>
For a leisurely four minute walk, no lag was apparent. For a
more brisk walk, a lag of about 2-3 seconds was seen. The GPS
refresh rate was set at 1 Hz (note: blue markers in figure
correspond to spots where a new GPS fix was gotten during the
walk).
</p>
<center>
<img src="./images/mem_glad.jpg" alt=
"Motion Tracking about Memorial Glade">
</center>
<hr />
<p>
Last Updated: $Date: 2003/07/28 16:47:45 $
by $Author: csm23 $.
</p>
</body>
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