Using a GPS Receiver to find a
site location.
When you are establishing a field site for any GLOBE protocol, one
of the first measurements that the students must make is to determine
the location of the site. The Global Positioning Satellites (GPS)
provide a relatively quick and accurate location which can be
improved in accuracy by averaging the readings taken every minute for
five or more minutes. This improved speed of measurement is due to
the recent (May 2000) deactivation of some of the GPS Satellite
imformation dithering features. Thus only about five minutes of data
need to be recorded (at one minute intervals).
Turn on the GPS receiver and let it acquire sufficient satellite
data to display position coordinates. Insure that the receiver is in
the open, (out of doors) has a charged battery, and is held still
near or on the surface to be measured. In most cases, the degrees of
latitude and longitude will remain the same throughout the process,
but the tenths and hundredths of a minute readings will fluctuate
similar to the displays illustrated below. Record the readings on the
display for later analysis. For clarity, each of the readings have
been entered as text to the right of each photograph.
Practical Exercise
1
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Given
a handheld GPS receiver with the following screen
photographs taken at one minute intervals,
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Calculate
the coordinates and altitude for the site to the nearest
0.01' (minute) of latitude and longitude and meter of
elevation.
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8 Sep 99 @ 00:01:00 UT
N 36°13.190'
W 092°19.045'
440 feet above MSL
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8 Sep 99 @ 00:02:00 UT
N 36°13.190'
W 092°19.038'
427 feet above MSL
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8 Sep 99 @ 00:03:00 UT
N 36°13.197'
W 092°19.032'
393 feet above MSL
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8 Sep 99 @ 00:04:00 UT
N 36°13.208'
W 092°19.031'
375 feet above MSL
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8 Sep 99 @ 00:05:00 UT
N 36°13.218
W 092°19.033'
410 feet above MSL
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Enter the values illustrated above on the GPS Worksheet
or an Excel Spreadsheet and calculate the averages.
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Answer
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