Airports are natural focal points for the development of
office buildings, factories, warehouses and hotels.
Although concentrated development enhances the economics
of aviation facilities, it poses safety concerns
regarding airspace obstructions in the immediate
vicinity of airports. Aviation authorities have found
such safety issues can be managed more effectively with
accurate 3-D mapping methods.
A Case in Point
In 2002, Florida’s Tallahassee Regional Airport
initiated a major mapping project to support a variety
of facility management endeavors, including obstruction
analysis. As is the case at airports around the world,
rapid development resulted in the placement of wireless
communication towers, buildings and construction cranes
in areas surrounding the airport. If placed improperly,
such vertical structures can interfere with the safe
operation of aircraft.
In recent years, airports have
started using advanced spatial 3-D simulation techniques
to model the nearby terrain and
aircraft-approach/departure paths to determine where
cell towers or construction cranes of specific heights
can be safely located. The basic concept behind
obstruction analysis is for airport authorities to
consult the model to approve the height and location of
vertical features proposed for placement on or near an
airport
A 3-D map that is accurate,
recent and shows the x, y and z dimensions of all
terrain and man-made features of an airport and within
several miles of the approach and departure ends of its
runways is the key data set required for successful
obstruction analysis.
With time and money in short
supply, the Florida Department of Transportation (FDOT)
Aviation Office turned to the FDOT Surveying and Mapping
Office to generate the required map data. Fortunately,
the Surveying and Mapping group had recently converted
its aerial photography processing string to an
all-digital workflow.
Using the digital processing
workflow—from mission planning to orthophoto
production—the group delivered a topographic map of the
entire six-square-mile project area less than eight
weeks after FDOT’s aircraft began collecting photos. The
final deliverables also included a digital terrain model
(DTM), triangulated irregular network (TIN) and
orthophotography at a total project cost about $50,000
less than the amount Florida taxpayers would have paid
prior to implementing digital technology.
A Digital
Approach
Headquartered in Tallahassee, FDOT is responsible for
managing the design, construction and maintenance of the
Florida transportation system, which includes 39,703
lane-miles of highway, 6,253 bridges, 828 aviation
facilities, 14 seaports and numerous railway lines. The
Surveying and Mapping Office supports these and other
activities by generating high-resolution engineering
imagery and cartographic maps customized for individual
applications. The office also provides a field crew for
some surveying projects.
In addition to the custom
project work, Surveying and Mapping acquires
high-altitude aerial photography for the entire state
every three years. With so much acquisition and
production work to be done, the office maintains its own
aerial camera, processing laboratory and aircraft for
acquisition. FDOT can plan and fly a project, process
the film, scan, make orthophotos and extract features.
Yet despite such internal mapping capability and its
associated cost savings, the department still farms out
a major portion of overflow image processing work to
private-sector contractors due to its heavy work load.
In the early 1990s, Surveying
and Mapping began a phased transition to a digital
workflow with the purchase of a film scanner and
Unix-based softcopy photogrammetry package from
Huntsville, Ala.-based Intergraph Corp. Intergraph later
formed Z/I Imaging Corp., which was a joint venture
between Carl Zeiss’ hardware solutions and Intergraph’s
software solutions. Intergraph currently owns 100
percent of Z/I Imaging.
With a keen eye toward saving
taxpayer money and an ultimate goal of creating an
all-digital workflow, Surveying and Mapping gradually
added new hardware and software products as Z/I Imaging
introduced them. FDOT was among the first purchasers of
many cutting-edge digital systems. By 2002, when the
Tallahassee airport project began, every production
phase was digital: photo scanning, triangulation,
feature collection, DTM collection and
orthorectification. Surveying and Mapping had even
installed digital systems for acquisition planning on
the front end, and has since added online data
distribution on the output side.
With the implementation of each
new digital system, Surveying and Mapping noted a
quantifiable time savings in overall production, which
translated directly into taxpayer savings. Just as
important, the digital technology dramatically improved
the efficiency of office personnel.
Mapping the Airport
The obstruction analysis project at the Tallahassee
airport entailed collecting high-resolution air photos
and producing orthophotos with a .40-foot pixel size.
Photo acquisition was conducted with Surveying and
Mapping’s Z/I Imaging RMK TOP 15 film camera (which is
being replaced by a digital camera) mounted in FDOT’s
twin-engine aircraft. The office started acquiring the
photos in April 2002, flying at 2,400 feet above ground
level.
To prepare for the flights,
Surveying and Mapping used Z/I Imaging’s ImageStation
Mission Planning System (ISMP) to plan the flight lines
and photo frame center points. A total of 249 frames was
planned to cover the Tallahassee airport and environs.
This mission plan then was uploaded into an Airborne
Sensor Management System (ASMS), a new Z/I Imaging
product that links with the Global Positioning System
(GPS) and inertial measurement units to guide a pilot
through precise flight lines and control a camera’s
operation. ASMS is designed to support a variety of
sensors from analog cameras to digital cameras, so FDOT
won’t have to buy additional flight management software
for its new digital camera.
During the flights, the ASMS
recorded the frame center points as well as the camera’s
pitch, roll and tilt. Once on the ground, the data were
downloaded into the softcopy photogrammetry system. FDOT
has equipped the Surveying and Mapping image processing
facility with four Z/I Imaging ImageStation Z digital
photogrammetric workstations and two copies of
ImageStation Stereo Softcopy Kits (SSK), which turn
Windows computers into digital stereoplotters that run
the digital ImageStation software.
During the airport project, FDOT
maintained a darkroom for processing black-and-white
film; color film processing was outsourced. After this
step, the negatives were scanned at 14 microns on
PhotoScan 2002 scanners, and the digital files were
uploaded into the ImageStation workflow. With the
position and orientation data from the ASMS,
ImageStation Production Manager then set up footprints
of the frames and calculated exterior orientation
parameters.
The files then were ready for
point extraction and triangulation in the system’s
automatic triangulation software. Technicians used a
variety of software applications within the ImageStation
to digitally display the stereoimagery, compile features
and generate DTMs. With inputs of the camera model and
DTMs, Surveying and Mapping personnel used Z/I Imaging’s
OrthoPro application to orthorectify the frames and
mosaic them into a seamless and tonally balanced image
of the entire project area.
The success of the Tallahassee
airport project illustrates the benefits of an
all-digital workflow in two ways. First, it enabled
Surveying and Mapping’s five-person processing staff to
work extremely efficiently. As one operator completed
automatic triangulation (AT), for example, two operators
digitized features while two others created the DTMs.
And because the software is easy to use, personnel
specialization has been minimized; most of the operators
can perform any of the processing functions.
The second digital advantage is
time savings. Automated software simply runs faster than
manual methods. In the Tallahassee airport project,
Surveying and Mapping quantified the following time
savings compared to manual methods:
• 50 percent time savings in AT
• 20 percent time savings in
feature extraction
• 30 percent to 40 percent time
savings in DTM generation
By mid-June 2002, Surveying and
Mapping had delivered the orthophotos, topographic maps,
TINs and DTMs to the FDOT Aviation Office. Converting
the digital files to the AutoCAD format desired by the
office was a simple procedure as the files were output
for delivery.
After the Tallahassee airport
project, Surveying and Mapping improved delivery—and
overall workflow—by adding Z/I Imaging’s TerraShare
product. The client-server system integrates with
desktop computers and workstations to move files through
production and distribution processes in a Windows
environment. TerraShare’s advantage is that it keeps
track of all data sets regardless of where they are in
the production cycle, plus it allows multiple users to
work on specific processing aspects simultaneously.
In the near
future, Surveying and Mapping plans to allow any FDOT
office using the departmental network to access
TerraShare. TerraShare will allow personnel anywhere in
the state to browse through the image archive, which
eventually will include 700,000 digitized photos and
maps, and select the appropriate data set. TerraShare
also will allow users to convert files to any popular
format and map projection, and download them directly
into their geographic information system (GIS) or
engineering design package.
Completing the Digital Enterprise In late 2003, the Surveying and Mapping Office
purchased the Z/I Imaging Digital Mapping Camera (DMC),
which will make FDOT one of the first organizations in
the world to have a digital workflow that includes
acquisition, processing and distribution. Known for its
image clarity and sharpness, the DMC is expected to
further reduce the office’s time and processing costs.
Moreover, the camera’s ability to collect panchromatic,
color and near-infrared imagery simultaneously will
provide additional benefits and cost savings.
The new camera’s digital acquisition technology
eliminates the need for film processing and scanning. As
a result, Surveying and Mapping expects to cut two or
three weeks out of its normal processing schedule. The
DMC also will allow the office to close its darkroom.
In the final analysis, the DMC is expected to save
Surveying and Mapping about $225,000 annually in staff
reduction, operating costs and overhead. Based solely on
these savings, the camera will pay for itself within a
timeframe that is acceptable for FDOT.
