Mary Potter, Keystone Aerial Surveys





Based in Philadelphia, Pennsylvania, Keystone Aerial Surveys provides airborne acquisition and image processing services to clients throughout North America. Services include digital imagery, lidar, magnetometer, thermal, and film data collection and processing through 14 fully equipped aerial survey aircraft, 15 flight crews, and a growing IT department. The firm has been in business nearly 50 years, so it has witnessed the aerial mapping industry's tremendous growth and technological advancement. We met with president Mary Potter and senior project manager and survey pilot Neil DiFranco at the recent ASPRS conference and later interviewed Potter.






What niche or segment do you occupy in the aerial mapping and photogrammetry world? How has that changed over the years?

Founded as a film aerial photography acquisition company, Keystone is evolving into a multi-sensor (digital and lidar) and data solutions provider. Now, in addition to providing our core acquisition services, we take advantage of available technology and the intellectual resources of our employees to provide additional value-added services.
Keystone has also developed a large image library, which is accessible through our web portal KASView. This library gives the professional land surveyor and the photogrammetric community access to current high-resolution stereo digital imagery of hundreds of cities, offering inexpensive alternatives to custom acquisition flights. The KASView library, with availability of the near infrared band in all our digital images and access to our historical archive of film imagery, supports environmental studies and change detections among other applications. The portal was created to advertise and sell our ever-growing inventory of digital, film, and aeromagnetic data and imagery acquired over the years.


What types of customers do you fly for? What geographic areas do you fly?

We fly for both commercial and government clients and try to keep the mix at about 50/50. We fly throughout the United States as well as Canada and Mexico from our main base in Philadelphia and our secondary base in Benson, Arizona. Over the last year, we have flown in 44 states and Mexico.


Are you seeing any new uses of aerial mapping or ones becoming more popular?

New uses of aerial mapping are evolving as sensor capabilities are being realized, along with the software developments that can use the increased dynamic range and multi-band capabilities of the new sensors. We see people applying more diverse layers to the imagery to produce ever-increasing mashups, providing more uses of basic imagery. All these factors seem to drive the need for imagery and data at higher resolutions and quicker turnaround.


What are some exciting projects you have flown lately?

In the spring of 2008, Keystone was contracted by a client to acquire Vexcel UltraCamX imagery over Washington, D.C. at a GSD (ground sample distance; distance over the ground covered by one pixel of an image) of 15 cm. This was a challenging project, as it required extensive coordination with several agencies. Flights over the White House, Capital Building, and Naval Observatory required precise coordination and the alignment of very restricting conditions.
In the late summer of 2008, Keystone acquired imagery of the Hurricane Ike aftermath in the Houston and Galveston, Texas area. Keystone acquired the specified area in a single day, again using our UltraCamX, by acquiring the imagery at an altitude that did not interfere with the burdened Houston air traffic control system. We were able to deliver the imagery to our client the day after the flight.


Do you work with surveyors on things like ground control? Do you see opportunities for surveyors in aerial mapping? How can they work with you to improve efficiency and accuracy?

For typical jobs flown for photogrammetric companies, our clients work directly with surveyors. Flights are coordinated with any necessary ground targeting efforts.
For large-area collections with ortho-imagery of a specified accuracy as the end product, we work with surveyors to collect ground control points for quality control and accuracy verification purposes.
With our growing library of images, opportunity exists for surveyors to compile coordinated sets of high-accuracy ground control points. Combined, these datasets would create very accurate ortho-imagery and precise elevation models for the country's most dynamic regions.
As airborne GPS (ABGPS) and IMU (inertial measurement unit) technology advances allow greater on-the-fly accuracies, users are requiring end products with even greater horizontal and vertical accuracies. Digital mapping cameras and lidar technology can produce extremely high-resolution products capable of supporting these accuracies. The skills of professional surveyors will always be essential in the creation of products with known, reliable, and quantifiable accuracy.


What formats do you work with most (digital, lidar, thermal, etc.), and do you often work with multiple formats?

We work primarily with digital and analog film cameras and have platformed lidar sensors. We do not typically combine more than one sensor in a single collection mission.


 How is the use of GPS changing in aerial surveying?

Most digital sensors, including camera and lidar, require ABGPS and IMU during collection of data to provide the position and orientation information necessary for post-processing. Collection of this referential data is a technical service supplied to mapping professionals who continue post-processing with advanced software and adds accurate survey data to produce highly authoritative and definite products to meet the needs of their clients.


How much of your work is flying and gathering data versus processing the data in the IT arena? How is that changing, particularly to accommodate digital imagery?

As we transition towards increased digital production, our IT department has evolved accordingly. With our traditional photography-based workflow, IT resources were used mostly to provide software support and job management functionality for film titling, processing, and quality control. With the addition of large-format digital sensors, our IT department has taken on a much larger role to provide the post-flight processing, storage, and delivery capabilities necessary for the large-volume production.
Significant investments in hardware, software, and personnel have been necessary to accommodate the new digital workflow. With customized software and hardware resources that allow highly distributed image processing, we can minimize the time it takes to push imagery through the production pipeline. This lets us continue to concentrate on high-capacity acquisition of imagery without getting backlogged with processing on the ground.
While we expect our digital data collection efforts to grow as we add more sensors to our fleet, we believe that work in the digital processing department will increase at a substantially higher rate. This is because there is significant opportunity to create value-added products beyond our basic image processing. Ortho-production, for instance, has its own workflow with additional processing, editing, and quality control requirements. Managing our resources to maintain optimum efficiency from collection of imagery through delivery of end products will be our challenge in the coming years.


Describe your work with airborne magnetometer data. How does that work? Tell us about your sister company Airmag Surveys and how you work with them.

Airmag Surveys, Inc. is a wholly owned subsidiary of Keystone Aerial Surveys that offers airborne fixed-wing data acquisition for the geophysical community with an emphasis on high-resolution aeromagnetic data. Aeromagnetics provides a fast, inexpensive method of evaluating basement and sedimentary discontinuities. Aeromagnetic is an excellent tool for exploring oil, natural gas, and mineral deposits, whether used at the regional scale for basin mapping or on a local scale for specific targets.
Our aeromagnetic survey experience dates back to 1944 when Aero Service performed geophysical experiments for the USGS using the soon-to-be declassified ASQ-8 submarine detector. In the years following, former Aero Service personnel continued their involvement in aeromagnetics as techniques and equipment evolved.
The magnetometer takes the form of a stinger mount at the rear of the aircraft, filled with cesium vapor and electrically charged. As the magnetometer passes over areas with different magnetic signatures, the cesium vapor density changes. The changes are digitally recorded along with high accuracy differential GPS, radar altimeter, and video data for flight path recovery.


What do you see as the most important advances in the aerial mapping industry, either in the past or taking place now?

The most important one is the advancement of digital collection and processing. The technical service we provide is quickly moving from analog to digital-driven mainly by the clients need for higher resolution multiband imagery. The film camera evolved slowly over time and is now realized and in a stable platform. The digital sensors are in the early stages of advancement with much growth needed to increase stability and affordability.

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