Independent Geo-Spatial Quality Review, Is It Really Worth the Extra Money?
A common question asked by
many purchasers of geo-spatial data is “Do we want to spend additional money for independent quality control (QC)”? The project may have been purchased as a low bid and money was saved, should you use
this saved money to contract with an independent QC provider for verification that the data was indeed collected and processed
as detailed in your scope of work? The potential always exists that the
data delivered may not be suitable for the intended mapping applications.
The industry is experiencing a reduction in geospatial
product pricing; this is in part due to the latest advances in sensor technology and processing software. The downside of these advances is that all providers, whether they have advanced systems or not, need to
collect and process data on tighter budgets and schedules. Even though vendors
have best intentions, errors and quality review can be overlooked when budgets are tight.
Independent QC provides multiple benefits
to the purchaser of LiDAR and/or imagery data. Not only do you have qualified
and unbiased external verification that your products meet all contracted specifications for accuracy and quality, it is also
a significant means to prevent error propagation for future data uses. If errors
are found in the data it is extremely helpful to have an experienced QC provider who can “speak the same language”
as the LiDAR providers to properly explain the issues to the clients and work with vendors to solve various problems. In the end you will be more confident
in your choice of data provider and your delivered product.
In general, Independent
QC verifies that all data products will meet detailed and not easily understood ASPRS, NSSDA, FEMA, NMAS or NDEP specified requirements, as well as custom project requirements. This usually involves field collection
of independent survey checkpoints to ensure the data set is accurate to its specified vertical and horizontal accuracy. Checkpoints are collected by a licensed surveyor and the amount and location are dependent
upon the specific defined project guidelines or specifications. These checkpoints
are then used as a basis for independently verifying the surface accuracy.
The QC provider should verify the quality
and integrity of the LiDAR and imagery data at various phases of the processing work flow as well as review any available
field, flight, calibration, processing and QC reports. The flight and calibration
reports provide valuable information concerning the flight conditions and the calibration accuracy of the missions. Processing reports typically reveal any issues encountered and solutions that were used to solve the problems. On the whole, these additional reports help to fill in the information gaps in the
project. They provide insight into the project and help the QC provider verify
the data integrity and reliability.
Joel Dudas with the California Department
of Water Resources is a strong advocate of independent quality review. He says,
“Independent QA/QC is not just a matter of getting some numbers adjusted and
decimal points being in the right place at a few dozen random control points. Product integrity doesn’t come from
just verifying specifications. Instead it’s more about having someone truly
financially disinterested, yet technically savvy, who examines the entire production process to insure data integrity and
reliability. That’s something only independent QA/QC gives you.”
Customary evaluations for LiDAR data include
reviewing for data voids, flight line seams, anomalies, excessive noise, artifact removal in bare earth surfaces, over-aggressive
filtering (smoothing), proper datum and coordinate systems, as well as edge matching.
Orthoimagery reviews typically include checking for complete image coverage, registration, edge matching, review of
geometric characteristics such as image sheer and distortion, radiometric quality, and horizontal accuracy.
The reduction of geospatial pricing is not the only reason for the growing need
of independent QC. All projects necessitate additional quality control even if the data vendor has a defined QC program. We see many projects being subcontracted or awarded to teams of vendors who are processing
various portions of the overall project. Some projects may have as many as 3 or 4 different groups collecting and processing
the data at the same time in various locations. In the end this data has to come
together to fit perfectly like a jigsaw puzzle. Were the flights acquired in
accordance to the contracted specifications? Was the processing completed the
exact same way in each location? Does all the data fit together seamlessly?
Additional costs for independent QC are small
compared to the unbiased assurance that your data is accurate and suitable for your future applications. Most customers agree that the sense of confidence in their data and reduced liability is worth the added
expense.
eMap
International LLC: The eMap Team
has a combined 80 years experience working in the geospatial industry with strong expertise in key areas such as LiDAR, photogrammetry,
remote sensing and GIS. eMap’s staff includes knowledgeable, independent,
and unbiased Certified Photogrammetrists, Certified Mapping Scientists and Professional Land
Surveyors that oversee all independent quality reviews. eMap International leverages
its understanding of LiDAR and digital image specifications and technical requirements to provide rigorous, independent quality
assurance programs to verify that all data products meet ASPRS, NSSDA, FEMA, NMAS, NDEP and other specified requirements. eMap works with clients to assess their quality needs, then builds programs necessary
to meet project requirements, and provides reviewed products on time and within budget.
For more information, please contact:
Jennifer Whitacre
Director of Project Design and Implementation
eMap International
Direct:
812-418-4462
Cell: 720-252-6840
Fax: 317-534-3777
jwhitacre@emap-int.com
