532
August 2017
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
•
Expedited processing.
•
Disseminating the data to responders, organi-
zations, agencies, etc.
In nearly every disaster response, the primary
acquisition involved imagery. However, in
the Joplin case we also decided upon LiDAR
acquisition and processing somewhat later to
assist with the engineering efforts. Potential
imagery acquisition assets include:
•
Digital airborne systems – fixed-wing or helicopter.
•
Satellite systems.
•
Unmanned Aerial Systems (UAS).
In Surdex’s experience, fixed-wing aircraft are the best
assets: they can be ferried to the site quickly (which may
be a long distance), they can capitalize on open windows of
weather, and they operate at higher altitudes that avoid
most temporary airspace restrictions. Satellite systems are
constrained by orbital mechanics, leaving them prone to
unavailability during key breaks in the weather. Most imag-
ing satellites are constrained to “morning” and “afternoon”
windows that may not find clear skies.
UAS’s are hard-pressed to cover large expanses in the short
periods of good weather and must be either present near the
site or transported to the site. Additionally, the often turbulent
weather may preclude acquisition by these light airframes.
Since acquisition missions must be pre-planned, there are
parameters that must be addressed before they are un-
dertaken. In some cases, news media accounts and visuals
provide enough information, but in other cases external
resources must be used.
For example, in the case of the Joplin tornado in 2011,
Surdex reached out to the Missouri Geographic Informa-
tion Systems Advisory Council listserv. Within hours of our
request, state employees provided Surdex with a shapefile
and we notified them of our intent to capture data. We later
learned that a local law enforcement official annotated a
map of the area during an aerial overflight, which was con-
verted to a shapefile that delineated the core area of damage
as well as the overall path of destruction through the area.
Resolution is dependent upon the desired usage of the data,
tempered by the size of the area and weather that may
interfere with timely acquisition. For example, it is a well-
known fact that hurricanes are followed by long stretches of
good weather as the system clears out. In contrast, flooding
and tornado scenarios are inherently followed by periods of
bad weather that can persist for days.
Many responses focus on 1’/30cm to 18”/45cm for a quick over-
view, especially for large area coverage such as from hurricane
destruction. This is a resolution adequate enough to determine
the level of damage to homes, businesses, etc. In general, Sur-
dex has focused on 1’/30cm resolution but has provided detail
at 6”/15cm to assist with detailed mapping at a later date. In
the case of Joplin, we also acquired 3”/7.5cm resolution data,
determining the very high resolution data would be valuable
for follow-up research of structural damage.
In some emergency response situations, temporary airspace
restrictions often come into play as the needs of responders,
news, and general public overflights are balanced for safety
reasons. In the case of the Meramec River event, there were
no airspace restrictions. In contrast, Surdex’s overflight of
Joplin was subject to airspace restrictions based on the mis-
sion-specific flying height, and one mission was hampered
by a helicopter-borne news crew that exceeded the altitude
limit and forced an abort of one imaging line.
Summary
Surdex was excited to provide this community service for
the Meramec River flood of 2017. With previous similar
experiences behind us, we were able to capture the imagery
at a timely point in the flood timeframe and use our tested
emergency response processes to ensure expedited products
to the government and the public. It is clear that dissem-
inating time-critical data is becoming easier because of
web mapping services and expanding broad-band internet
availability. It is also clear that the GIS professionals within
state and federal agencies are keys to ensuring such data is
provided to the necessary responders and decision-makers.
Surdex Corporation of Chesterfield, Missouri
is a
privately owned aerial mapping company celebrating its
63rd year of continuous operation. The company’s services
include orthoimagery, LiDAR acquisition and processing,
planimetric mapping, topographic mapping, and web host-
ing services. The company currently owns and operates:
•
Ten aircraft, including four high-performance, twin-tur-
bine Cessna 441 (Conquest) aircraft, and twin- and
single-engine piston aircraft.
•
Five Leica ADS100 large-format, digital pushbroom
cameras, four Leica DMC-1 large-format, digital frame
sensors, two OpTech Galaxy LiDAR sensors, and a
Leica RCD-30 oblique camera system.
Surdex’s clientele include local, state, and federal govern-
ment as well as private engineering.
Shapefile illustrating total extent (yellow) and core destruction (red) overlaid over final
mosaic used for the Joplin tornado response.
