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Method:
I made a square of 200 x 200 m with a steel measuring tape, checked the diagonal and angles of to corners.
So I´ve got fairly correct an area of 4 ha. Then I did some measurements with GPSMeter PDA 1.67
Static navigation was turned off. The GPS antenna (HI 303 MMF) was connected with Bluetooth (BT 401)
and was fixed on a mount 2 meter overhead ground, so there were no effects disturbing recieving GPS signals from car or persons.
I am using the average function for 5 different test. WGS 84;UTM-grid.
| Results: |
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Test number |
GPS Status |
Sats in use |
PDOP |
Times of measurement per point |
Area (ha) |
Area relative error (%) |
Perimeter (m) |
Perimeter relative error (%) |
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1 |
DGPS |
7 |
2.5 |
400 |
3.9943 |
-0.14 |
799.51 |
-0.06 |
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2 |
DGPS |
7 - 8 |
2.5 |
10 |
3.9767 |
-0.58 |
797.76 |
-0.28 |
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3 |
3D |
8 |
2.3 |
20 |
4.0239 |
0.60 |
802.5 |
0.31 |
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|
4 |
DGPS |
10 |
0.8 |
10 |
3.9895 |
-0.26 |
799.95 |
-0.01 |
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5 |
3D |
9 |
0.8 |
10 |
4.0144 |
0.36 |
801.73 |
0.22 |
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Expected Area (ha) |
4 |
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Expected Perimeter (m) |
800 |
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| Conclusions: |
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In all test the relative
error of measured area is less than 1% |
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For the test 1 where DGPS
corrections was combined with very large time of measurement per point, the
relative error of measured area is drastically low |
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Test 2 and 3 have
practically the same relative error in the measured area. Test 2 have the
half of the time of measurement per point than Test 3 but the DGPS
corrections were used. |
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Test 4 and 5 was carried
out the next week with the version 1.70 of GPSMeter PDA. The values 0.8 are
for HDOP rather than PDOP (the HDOP filter was fixed to 2.0) |
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This last test shows
clearly that the accuracy is better when the sats number is higher. |
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