From the Ground Up
Have you spent much time thinking of how the application of new technology has impacted your professional career? Regardless of your specialty, technology has almost certainly had a significant effect on the way you conduct your day-to-day business.
The impact of new technology in the mapping arena over these last few years has been profound. Mapping is very different today than it was just a few short years ago thanks to technological advances. And the impacts are felt in all areas: on the ground, in the air and in the office. Let’s take a look at some of the changes that have occurred over a short period of time.
GPSAny discussion of the impacts of technology in surveying and mapping would not be complete without a discussion of GPS. The impact from GPS in establishing photo control for mapping projects has been significant. In general, the cost of setting photo control for a mapping project is just a fraction of what it was 10 years ago thanks to the wonders of GPS. Yes, labor rates have gone up over that time span, but they have been more than offset by the increased production rates.
The impact of GPS is significant beyond just cost. The accuracy available from precise, dual-frequency GPS observations is far better than what we expected from conventional surveys. Furthermore, GPS control can be established in a fraction of the time when compared to conventional surveying, allowing projects to be completed in a shorter time frame. Finally, we gain a lot of flexibility in terms of options for establishing control with GPS. For example, code-phase, differential GPS (DGPS) observations can provide us with sub-meter accuracies in photo control at a small fraction of the cost of more precise static or RTK observations. And there are a lot of mapping applications where sub-meter control works very well.
GPS is also a very important enabling technology. For example, it is the heart of flight management systems that most aerial photography firms use today. Flight lines were flown just a few years ago by sight. The pilot would hold a map with the flight lines marked in heavy marker in one hand, look out the window to find features on the ground that would allow them to line up the plane on the flight line, and try to maintain the proper heading and altitude along the line to capture the photography. As you might imagine, that was an incredibly difficult task. Even the most experienced flight crews would have to re-fly some 5 to 10 percent of the flight lines because the photos weren’t taken in the right spot.
Flight lines today are planned in the office, downloaded on a diskette, and uploaded into a flight management computer in the airplane. GPS provides updated three-dimensional positions of the aircraft during the flight to the flight management computer. The pilot guides the plane along the flight lines shown on a display that mounts on the dash. No more paper maps. No more missed flight lines. The impacts on quality and production are significant.
Finally, GPS has provided the industry with exciting new ways to control photography from the air instead of on the ground. Airborne GPS (ABGPS) control, where the three-dimensional position of the camera is accurately determined for every photo captured during a flight mission, became fairly common in the mid- to late-90s. More recently, the addition of inertial measurement units (IMU’s) to ABGPS has resulted in the solution of the camera rotation from the IMU. The result, known as direct geo-referencing, provides all the variables necessary to go directly from photography to mapping without any intermediate steps along the way. This technology is incredible and can have a significant effect on the amount of time it takes to complete a project while reducing project cost. And it is gaining popularity in the industry. However, the initial price tag of over $200,000 for the IMU and controller keeps some players out of the market.
LIDARLIDAR is a very hot topic in the surveying and mapping fields today. A cousin to radar, LIDAR technology is used to produce a digital elevation model of a project area in short fashion. How does it work? The LIDAR unit is mounted in the belly of an aircraft and flown back and forth over a project site.
The LIDAR unit sends out many pulses of energy that travel to the ground, are reflected, and return to the aircraft. Distance is determined from the time it takes the pulse to travel to the ground and back, much like distance is determined in a total station. ABGPS provides the position of the LIDAR at the time each pulse of energy is sent and an IMU provides the three-dimensional pointing angle of the LIDAR unit. The three-dimensional position of the ground is determined from the distance, position and direction gained from LIDAR for each pulse. This process is repeated some 20,000 to 25,000 times each second of flight. The data gained from a LIDAR mission is obviously overwhelming to most. But software written specifically for this kind of data is able to reduce it to meaningful ground elevation information, which can be put to use in many ways.
Due to cost considerations, this exciting technology is most commonly used on large projects. But as we have seen in the past with other advances, costs will continue to diminish to the degree that smaller projects will become candidates as well.
Digital CamerasDigital camera technology has reached a point where it is beginning to have a widespread impact on mapping projects. Look for a lot more digital systems to be installed in mapping shops over the next few years. But the technology still comes at a fairly steep price tag. Top-of-the-line systems today can be as much as $1.5 million. Other high-end digital cameras, however, can be purchased in the $350,000 price range. This is fairly comparable to the price of film-based photogrammetric camera systems available today.
What advantages do digital cameras provide over conventional film cameras? For most projects a cost and time advantage. And isn’t that what we’re always trying to improve (along with quality) for all projects? When photography is captured on film, the film must be processed, lab products made, and image scans performed before digital imagery is available for the production process. This can take days or weeks and result in costs of $25 or more per frame of photography. And that cost doesn’t include the cost of the raw film used in the camera, which can add several more dollars depending on film type.
Why haven’t all mapping firms added digital cameras to their planes? There are a number of reasons—initial cost, rapidly changing technology and a smaller image footprint in the digital sensors are the most influential. Like any new technology, digital cameras have undergone huge changes over the last couple of years. Accuracy has improved, resolution has increased and costs have dropped. Most in the mapping industry have been waiting for the technology and cost curves to flatten out somewhat before diving in. The technology has matured a great deal over the last few years and changes won’t be so dramatic over the coming years.
On the downside, digital cameras typically have a smaller image footprint (the area of ground covered in each photo) than their film-based counterparts. Therefore, for most projects, more flight lines and more photos are required to cover the project area. This has an impact on both the aerial photography costs and the costs of mapping that result from production from the increased number of images.
Satellite ImageryIt wasn’t that long ago that satellite imagery had limited applications in the surveying and mapping arenas because of the limitations on the resolution in the imagery. This is another area where the technology has undergone significant changes in the last few years. Space Imaging’s (Thornton, Colo.) IKONOS satellite was the first to provide a resolution of 1-meter from satellite imagery. Moreover, Digital Globe’s (Longmont, Colo.) QuickBird 2 satellite was successfully launched in October of last year. This new satellite provides the highest resolution imagery available to date from a space-borne system with a resolution for its black and white imagery of 61 centimeters, or 2 feet.
The new high-resolution imagery available from Space Imaging and Digital Globe rivals that available from higher altitude aerial photography flights. Satellite imagery can be cheaper than traditional photography, depending on the project. By nature, satellite imagery covers large block areas on the ground and therefore is better suited for larger projects. Small, linear or irregular-shaped projects will still be best served by conventional aerial photography.