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PETROLEUM DIRECTORY: Measuring, mapping the earth’s surface AeroMap provides a wide range of aerial photography, remote sensing and geographic information system services Alan Bailey Petroleum Directory Contributing Writer
The use of computers to manipulate maps is dramatically improving the efficiency of anything from urban planning to oil and gas exploration. And aircraft or satellite-based systems for acquiring so-called geospatial data — images and other data that describe the earth’s surface — are transforming mapmaking from a labor-intensive handcraft into a rapid, automated process.
AeroMap U.S., based in Anchorage, Alaska, sits at the forefront of this technological revolution. The company’s three aircraft, high-tech equipment and state-of-the-art computer systems provide customers with a complete range of services for capturing and processing geospatial data.
“The company was founded in 1960 by Casey Fesperman,” Tony Follett, senior vice president of AeroMap, told Petroleum News.
The company, originally called Air Photo Tech, merged with North Pacific Aerial Surveys in 1988 to form AeroMap. In 1993 Wisconsin-based Aero-Metric Inc., which owned Walker Alaska Aerial Survey, acquired AeroMap. The Alaska business has continued to operate under the name of AeroMap U.S.
The company services a wide variety of clients in Alaska, as well as elsewhere in the United States and internationally. Aerial photography From the outset, aerial photography has formed the core of the company’s business.
For map production, an aircraft equipped with a special, large-format camera shoots photographs vertically downwards. The aircraft follows a straight track at a set altitude and the camera fires every few seconds, to achieve about a 60 percent overlap between adjacent photos. This overlap enables the photos to be viewed as stereoscopic pairs when extracting elevation information from the images.
“It’s all controlled by airborne GPS systems,” Follett said.
The camera setup also uses inertial measuring units — the same devices that are used for navigation on intercontinental ballistic missiles, Follett explained.
“These very finely determine the attitude, so every time we take a picture ... we know precisely where (the camera) is ... it’s automatically fired by a computer system when you travel a certain distance or for a certain number of seconds,” Follett said.
Digital photography has also entered the aerial photography business. The corporation now owns a digital mapping camera with a ground resolution that can be as fine as two inches.
Although map production requires vertical images, customers often want oblique aerial photographs to illustrate locations.
“For most people that’s how they’re used to looking at things — from an angle, not looking straight down,” Follett said.
Over the years AeroMap has amassed a huge library of both vertical and oblique aerial photographs.
“We’ve got aerial film that goes back to 1939 here in our library,” Follett said. “We’ve probably got well over 1.5 million negatives in our library.” Satellite imagery AeroMap also markets satellite imagery.
“We are the Alaska reseller for DigitalGlobe, which is a company that has the highest resolution commercial satellite available today,” Follett said. “It’s got about a two-foot pixel resolution from space.”
The satellite images prove especially valuable for applications such as wildlife surveys or mapping the distribution of ground features.
“For example, on the Kenai Peninsula there’s a lot of interest in using satellite imagery ... for detecting and determining how large the spread of bark beetle infestation is,” Follett said. Laser aerial surveys One of the newest techniques for aerial surveying involves firing pulses of laser light at the ground and timing the reflections that return to the aircraft. This technology, known as LIDAR, accurately measures ground elevation points at the rate of 70,000 per second from an aircraft sweeping across an area.
LIDAR gathers data as a string of elevation coordinates that form a so-called digital terrain model — a computer model that can generate colored perspective images of the ground relief as well as conventional contour maps.
“LIDAR is rapidly growing in popularity throughout the country because it’s fast,” Follett said.
The narrow beam from the laser system can penetrate gaps between vegetation, so that even in heavily forested areas the sensor on the aircraft can pick up reflections from both the top of the vegetation and the underlying ground. Computer processing of the LIDAR data can then strip out the reflections of the ground cover, including buildings and other structures, to reveal the precise shape of the ground surface. Radar surveys Radar aerial surveys work in a similar fashion to LIDAR but use radar pulses rather than a laser system. The resolution’s not as good as the laser-based system and radar can’t penetrate vegetation as easily. However, radar provides a quick and efficient way of mapping large areas, either using an aircraft or from a satellite. Also, radar surveys don’t require clear weather because the radar transmissions can penetrate clouds.
AeroMap represents a company called InterMap Technologies that does radar surveys from a jet aircraft flying at 30,000 feet.
“We did it up in NPR-A for the Bureau of Land Management,” Follett said. “We provide aerial photography and they’re using radar for determining the ground surface shape.”
AeroMap also resells and processes satellite radar survey products from Radarsat.
The whole arena of remote sensing from the air extends into other technologies such as sensors for specified wavelengths of light and thermal sensors for picking up heat patterns. Thermal remote sensing, for example, supports many applications such as monitoring effluent discharge and looking for leaks from underground steam lines. Data processing In addition to doing aerial surveys, AeroMap operates a complete suite of data processing services for geospatial data and aerial photographs. For example, a computer system converts raw aerial photographs into orthophotos that have squared-up, accurate horizontal dimensions.
As part of its geographical information system services AeroMap can organize any form of geospatial data into computer files designed for displaying or analyzing data.
“We design geographical information systems, populate the systems ... convert data from one system to another,” Follett said. Image processing systems can use a digital image of an area to generate maps that depict ground features such as different types of vegetation. A ground-based expert identifies what is on the ground at a location and an AeroMap specialist locates the so-called digital signature or pattern that represents the ground feature in the image. Then a computer program can use the digital signature to map the feature throughout the area of the image.
“We have a project with Fish and Wildlife Service to help with their national wetlands inventory, for classifying what’s wetlands and what’s uplands, what’s bare earth,” Follett said. Teamwork Success in all of this work depends on a multi-skilled team of pilots, surveyors, geologists and so on.
“We have 65 people and they have just a wide range of backgrounds,” Follett said. “We have a number of folks who are certified photogrammetrists ... we have two licensed surveyors on the staff right now.”
But the team at AeroMap shares a common purpose of helping people improve the world that we live in. The use of maps and geospatial data has become a crucial part of such essential activities as building roads, mitigating natural disasters and providing security.
“Our business is increasingly important to improve the quality of life — we’re involved in things that make a difference in people’s lives,” Follett said. “Really, an unseen but very important part of our society is having good-quality geospatial data.”
Editor’s note: Alan Bailey owns Badger Productions in Anchorage, Alaska
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