TY - JOUR
T1 - Accuracy of GPS telemetry collar locations with differential correction
AU - Moen, Ron
AU - Pastor, John
AU - Cohen, Yosef
PY - 1997/4
Y1 - 1997/4
N2 - Global Positioning System (GPS) units in telemetry collars provide an unbiased and precise estimate of animal locations. Under ideal conditions at least 50% of locations are expected to be within 40 m in uncorrected mode GPS, and within 5 m in differential mode GPS. When the collar was placed under open sky, most locations were 3-dimensional locations that could be differentially corrected. Under hardwood canopies with leaves on, the frequency of 3-dimensional locations decreased, the frequencies of failed location attempts and 2-dimensional locations increased, and the precision of GPS locations decreased. We compared the precision of each GPS mode by calculating uncorrected mode and differential mode locations from the same pseudo-range and ephemeris data. We varied the number of satellites used in the location solution to simulate the effect of decreased satellite acquisition due to canopy cover of precision of locations. Precision of locations increased if signals from >4 satellites were used to calculate the location in uncorrected mode and in differential mode. We found that 2- dimensional locations were almost as precise as 3-dimensional position positions if the altitude of the GPS unit was known. If the altitude used to calculate a 2-dimensional location was within 50 m of the actual collar altitude, the precision of 2-dimensional differential mode locations mode locations was better than 3-dimensional uncorrected mode locations. If the error in altitude was 100 or 150 m, then 50% of 2-dimensional differential mode locations were within 70 m and 95% were within 185 m of the true location. We used GPS locations from collars placed in different cover types and on free-ranging moose (Alces alces) top determine the effect of season, time of day, rainfall, and cover type on GPS performance. On free-ranging moose the collar GPS unit found ≤4 satellites on 52% of location attempts, >50% of locations were 3-dimensional, and >24% of locations were 2- dimensional. Precise tracking of individuals animals in al weather throughout the year is possible with GPS telemetry.
AB - Global Positioning System (GPS) units in telemetry collars provide an unbiased and precise estimate of animal locations. Under ideal conditions at least 50% of locations are expected to be within 40 m in uncorrected mode GPS, and within 5 m in differential mode GPS. When the collar was placed under open sky, most locations were 3-dimensional locations that could be differentially corrected. Under hardwood canopies with leaves on, the frequency of 3-dimensional locations decreased, the frequencies of failed location attempts and 2-dimensional locations increased, and the precision of GPS locations decreased. We compared the precision of each GPS mode by calculating uncorrected mode and differential mode locations from the same pseudo-range and ephemeris data. We varied the number of satellites used in the location solution to simulate the effect of decreased satellite acquisition due to canopy cover of precision of locations. Precision of locations increased if signals from >4 satellites were used to calculate the location in uncorrected mode and in differential mode. We found that 2- dimensional locations were almost as precise as 3-dimensional position positions if the altitude of the GPS unit was known. If the altitude used to calculate a 2-dimensional location was within 50 m of the actual collar altitude, the precision of 2-dimensional differential mode locations mode locations was better than 3-dimensional uncorrected mode locations. If the error in altitude was 100 or 150 m, then 50% of 2-dimensional differential mode locations were within 70 m and 95% were within 185 m of the true location. We used GPS locations from collars placed in different cover types and on free-ranging moose (Alces alces) top determine the effect of season, time of day, rainfall, and cover type on GPS performance. On free-ranging moose the collar GPS unit found ≤4 satellites on 52% of location attempts, >50% of locations were 3-dimensional, and >24% of locations were 2- dimensional. Precise tracking of individuals animals in al weather throughout the year is possible with GPS telemetry.
KW - Alces alces
KW - Bias
KW - Differential correction
KW - Global Positioning Systems GPS
KW - Moose
KW - Precision
KW - Radiotelemetry
KW - Rain
KW - Satellite availability
KW - Summer
KW - Winter
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U2 - 10.2307/3802612
DO - 10.2307/3802612
M3 - Article
AN - SCOPUS:0030619078
SN - 0022-541X
VL - 61
SP - 530
EP - 539
JO - Journal of Wildlife Management
JF - Journal of Wildlife Management
IS - 2
ER -