Tip:
Highlight text to annotate it
X
To ensure that the final horizontal RMS ground accuracy is at the GSD level, a simple "QA/QC
block" should be flown during each mission. This allows the geometric information of the
image block to be combined with the independent information in the EO measurements (provided
by your direct georeferencing system) in order to automatically check the quality of the
system calibration and to verify the accuracy on the ground. You are basically completing
a simplified boresight calibration. Here are SEVEN characteristics to setup a
QA/QC Block. 1. The QA/QC Block is ideally composed of
a block of images with a minimum of 3 strips, with opposing flight direction, and 8 images
in each strip Remember, a QA/QC Block can be flown at any
time during the mission • For Block missions, a smaller QA/QC block
can be simply subtracted from the full block, • For Corridor and Single Photo Missions,
3 additional flight lines of 8 photos can be simply added to one of the existing strips
at very little effort and cost 2. You must have your existing Airborne Geometric
Calibration Report prior to any flight mission. These are your most recent boresight calibration
report in conjunction with your latest camera calibration report
3. In the block, the image overlap should be 60% forward (minimum) and 20% sideward
(minimum) 4. Make sure the QA/QC block has many features,
ideally urban area because the QAQC procedures will create tie / pass points. You don't
what farm fields or golf courses 5. A few (2-3 minimum) Ground Control Points
(GCP) are recommended in the QA/QC Block to • Resolve any datum shift or GPS base station
coordinate issues • Detect any lever arm error
6. GCP accuracy is required to be within 5 cm horizontally and 5 cm vertically
7. GCP points are suggested to be Differential GPS surveyed using the same GPS Base Station
location and coordinates as the Airborne Calibration Flight. This minimizes datum transformation
errors. You should have airborne geometric calibration
software. Run this with your QAQC block data. You will create Refined Calibration Parameters
that are mission specific values. You have re-calibrated you Xp/Yp, boresight values
and local datum shift. If the changes are significant, apply the results to the current
project flight only. If your results improve your accuracy, it
is very likely that something in your sensor system shifted. You should strongly consider
performing a complete airborne geometric boresight calibration.
This is GeoErnest.