PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
July 2020
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Solution
Using equations 3, 4 and 5:
AccXTrueDatum =
= 3.61cm
AccYTrueDatum =
= 3.61cm
AccXYTrueDatum =
= 5.1cm
The value of 5.1cm is the true accuracy of the product versus the following value of 4.24cm used commonly today that
ignores the errors introduced during the ground surveying process:
AccXYTrueDatum =
= 4.24cm
Figure 4: Vector representations of error components.
Computing Vertical Accuracy
Similarly, for vertical accuracy determination of elevation
data derived from lidar or photogrammetric methods, we
need to consider the error in the surveyed elevation as an
important component. Using error prorogation principles
and Euclidean vector of Figure 5, we can derive the following
value for vertical product accuracy:
AccZTrueDatum =
6
As an example, when modeling vertical product accuracy
according to the above formulas, let us assume the following:
a) That we are evaluating the vertical accuracy for a
mobile lidar dataset using independent checkpoints.
b) The control survey report states that the survey of
the checkpoints, which was conducted using RTK
techniques, resulted in an accuracy of RMSEZ equal
to 3cm.
c) When the checkpoints were used to verify the
vertical accuracy of the lidar data, it resulted in an
accuracy of RMSEZ equal to 1cm.
Solution
Using Equation 6:
AccZTrueDatum =
= 3.16cm
The value of 3.16cm is the true vertical accuracy of the lidar dataset versus the value of 1cm, derived by the mapping tech-
nique used commonly that ignores the errors introduced during the ground surveying process.
