CHAPTER 9 - BIAS
9-4
HOW TO DETERMINE DATA COLLECTION BIAS
You can easily determine how much Bias there is on a particular pavement surface by
knowing either
The true elevations of the start and end points, or
The relative elevations of the start and end points, or by
Starting and ending a Run at the exact same location.
Since Bias is a constant with each step, if you know the total elevation error, you can
simply divide the total error by the number of steps to get the Bias error per step. You
could subtract this small error from each Reading, and the result would be a true profile
with no Bias.
How To Calculate and Remove Data Collection Bias Using A "Box" Run
Collect the data in a "Box" as shown in Chapter 4, COLLECT.
UNBOX the data as shown in Chapter 5, PROCESS.
The Data Collection Bias will automatically be calculated and removed from all 4 legs. It's
that easy. The key is to “close the loop” very precisely by hitting on the exact same spot
where you started. This is the Normal way to remove Data Collection Bias.
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