IMAGENEX DT101Xi, Technical Manual

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Doc no: 430-041-01 24 of 64
Figure 4-2
[Sketch courtesy of A Godin]
Data should be logged keeping speed changes (per run) to a minimum.
During processing, a subset of the feature / slope along the most pronounced point at nadir should be
extracted and processed using the patch test utility in the MBES processing package.
The output of this process should be the latency offset, that when applied would bring the feature / slope
points (at the different speed runs) to the same spatial location.
It is recommended that more than one set of high and low speed lines are run over the feature / slope
selected. Each set should be processed, an average value derived and used.
The Surveyor should verify that the along-track profile obtained by the highest speed, precedes the lowest
speed profile. If not, the time delay will be positive (MBES clock is late with respect to positioning system
clock) or the time delay applied during acquisition was overestimated.
The lines with the time delay correction entered should be re-merged and the along-track profiles replotted.
Time delay correction should be fine-tuned until one obtains the best match. Once satisfied and correctly
entered, a note of the latency correction should be made in the log book.