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GPH 492/692
description
Transcript of GPH 492/692
GPH 492/692GPS/Survey Team Results
Spring 2010(to support gravity survey)
Jay GoldfarbCourtney MurphyGarry RichardsonJason Henderson
SUMMARY OF METHODS Trigonometric leveling (total station) for upper
Hidden Valley gravity points (with one GPS elevation)
Mapping-grade GPS (Trimble ProXH) on remainder of Hidden Valley, Prater Way, and City of Sparks gravity reference points
Maps produced using .kml files imported into Google Earth
SURVEY RESULTS Estimated horizontal accuracies are
between 10 cm – 10 m (upper Hidden Valley points), due to different grades of GPS used for location.
Estimated vertical accuracy ranges from 10 cm to 75 cm, depending primarily on time of day of GPS data collection. (poor GDOP in afternoon)
(all estimates at 68% confidence level)
EFFECT OF HORIZONTAL POSITION ERROR ON GRAVITY ESTIMATION
Effect of 30 m error in latitude on normal gravity calculation:
EFFECT OF ELEVATION ERROR ON GRAVITY CALCULATION
2/67.2
)04192.03083.0(
cmg
mhmGaldghdg
-> a 20 cm elevation error results in 0.04 mGal error
-> a 75 cm elevation error results in 0.15 mGal error