758
October 2016
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
SECTOR
INSIGHT:
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com
and DSMs can have significant and measurable effects on the
ultimate accuracy of map products independent of the drone
manufacturers specifications.
Positional accuracy standards exist. The ASPRS has
defined accuracy standards for our profession. There are
others. ASPRS is actively developing a certification for UAS
operators with the hopes that professional UAS certifications
will help consumers of our mapping products in every
industry have some assurance that the UAS operators are
knowledgeable, competent mapping professionals. Methods
to ensure, describe, and test the positional accuracy of the
mapping products derived from drones are still important,
and perhaps more relevant than ever precisely because
drones have made remote sensing and mapping so easy and
accessible to the non-professional.
Finding the ground is hard. It is physics.
It separates the amateur from the professional. It is an
imperative for our remote sensing profession to communicate
standards and best practices to the thousands of budding
new professionals enabled by drone mapping technology.
The health and safety of the public and the dependability
of our drone mapping products and services depend upon
knowing where the ground is. Our profession and ASPRS
have a tremendous opportunity to attract and connect with
these new drone mappers and help them quickly mature into
professional mappers that use remote sensing technology
competently and can confidently answer “Where’s the
ground?”
Mike Tully, MS, MBA, GISP, President and CEO of Aerial
Services Inc. (ASI) and board member of MAPPS.
DEM is the default output from lidar sensors and traditional
mapping from aerial photography. Drone software (at least
currently) is incapable of producing digital “elevation” models
using aerial imagery if the ground is obscured. If obscured,
then the location and elevation of the “ground” cannot be
known. For many (not all) drone applications this is a show-
stopper. For applications like real estate photography,
infrastructure inspection, and film making, DSMs are not
a limiting constraint on producing valued products. But for
mapping and surveying applications where the location of
the ground is necessary, it is critically important the drone
operator understand this limitation of current technology.
It is common to meet drone operators that marvel at the high
resolution orthos they have produced from their new drones
but that had no idea about how accurately features are posi-
tioned on the earth. They don’t even know how to determine
nor describe that positional accuracy. The drone specifica-
tions say “accurate to 5 cm” so they assume everything in
their maps are located with that precision. They may have
never heard of “ground control” or considered that knowing
where the ground is could be important. What is the position-
al accuracy of my orthophotography or 3D map? How reliably
can I reproduce products with this accuracy using this drone?
What professional liability do you carry for the positional ac-
curacy of your maps?
Positional accuracy is impossible to know without testing
the data. Testing the data requires the use of ground control
points that are precisely surveyed on the ground and visi-
ble in the aerial photography. There are no shortcuts (yet!).
Professionals understand the limitations of their technology.
Non-metric plastic lenses are seriously flawed compared to
metric glass lenses. CMOS cameras introduce errors in imag-
ery like the
rolling shutter
problem that CCD cameras don’t
share. Added to technological limitations, the procedures
used by mapping technicians to create maps from imagery
This is really where the
line between amateur and
professional remote sensing,
surveying, and mapping
designation occurs. Where is
the ground?
Positional accuracy is
impossible to know without
testing the data.
STAND OUT FROM THE REST
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IMAGING & GEOSPATIAL
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ASPRS Certification validates your professional practice and
experience. It differentiates you from others in the profession.
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