By Phase One
The need for aerial data has increased significantly since new technology has brought about changes in the way data is acquired. With the ease of integrating cameras into aircraft, users are looking for ways to reduce their costs even more. Even though prices per square kilometer of mapping or orthophoto are much lower than in the past, companies are thinking of ways to reduce production costs and increase their return on investment. Phase One has solutions that can help reduce one of the biggest expenses — flight time.Read more
Flight costs are based on three factors:
• Time — the amount of time the aircraft is in the air, which is determined by the number of lines needed to fly.
• Altitude — the higher the plane climbs, the more fuel expended.
• Takeoff weight — the heavier the takeoff weight, the more fuel expended.
Direct savings are achieved by reducing the number of lines to fly. This is possible by covering a wider swath on the ground, which can be done by using a larger sensor, most often found in heavier, large format cameras.
There is only one way to increase the swath on the ground and that is to increase coverage with more airborne pixels. Using a heavy large format camera involves flying with a higher takeoff weight and spending more on climbing to the necessary altitude to capture the wider lines.
An alternative that has been quickly gaining in popularity, is to fly with several light weight medium format cameras connected in an array that are easy to integrate into a smaller aircraft. Using this system, operators can use less expensive aircraft, which means lower operation costs. By decreasing the payload weight, fuel expenses drop, translating into further savings.
The pixel count of medium format cameras has reached the size of some of the large format cameras. While a single medium format camera may not have the exact same resolution as a large format camera, combining two or more medium format cameras to create a synthetic large format, enables users to capture swaths that rival even the largest large format cameras.
One of the advantages of creating a synthetic large format is that the cost of buying cameras to make a synthetic large format are a fraction of an actual large format camera.
The easiest way to enlarge the swath with medium format cameras is to combine two or more of them in a slight oblique array and have the images overlap by a minimum of 10 percent, depending on the stitching or post processing software used. The stitching software normally calculates two to four images into a virtual plane and removes the lens distortion effects at the same time. To get the best
results from a stitching software, the interior orientation of each camera must be known and the exterior orientation of two or more cameras to each other as well. The interior orientation for each camera can be calibrated and the exterior orientation is normally determined in a boresight calibration flight. If we take as an example, two Phase One iXA-R 1000 70 mm cameras with an overlap of at least 15 percent, it would result in a swath on the ground which increases from a 11 k cross-track coverage to 19 k+ pixel with an opening angle of approximately 65 degrees.
The same can be done with three cameras in a row. In this case, we take as an example the iXA 1000 with a Schneider-Kreuznach 110 mm lens and an overlap of 30 percent, the end result would be a 24 K swath size with an approximately 100 degree opening angle. The examples mentioned above use a landscape oriented sensor configuration. But, a portrait configuration can be constructed as well, which produces more of a square footprint than a rectangle. Looking at these examples it is apparent that virtually any combination of cameras can be joined together to create a synthetic large format and fit the needs of a particular mission or project.
Another important consideration in creating a synthetic large format is the synchronization of the multiple cameras. Two factors are crucial in ensuring the multiple images serve their purpose; the precision of the synchronization and the consistency. Phase One aerial cameras are equipped with electronically controlled shutters, which have a synchronization time of 100 micro seconds andare consistent in this delivery time. The cameras are daisy chained together to ensure synchronization of data and signals. If the camera at the end is connected to an IMU/ GNSS, the data returned from the IMU/GNSS is written to the EXIF of each image. In order to build a synthetic large format, a special mounting plate or pod needs to be installed. This can be done independently or purchased from one of the Phase One integrators located around the world. Some customers prefer to use these configurations inside their existing gyrostabilized mounts. The Phase One iXU cameras are ideal for this scenario, because the small camera size enables users to mount up to four or even five cameras within the large format gyro mount.
The Phase One cameras are flexible enough to be used one day in a synthetic large format and the next, split up and used in different aircraft. This also opens up the possibilitiesfor users to employ the cameras in different configurations, both manned aircraft and UAVs.
Phase One aerial cameras, with high resolution sensors, are at the top end of medium format systems today. With their small size, and the ease at which they can be connected together, they create a powerful solution dimishing the need for a large format camera. Multiple cameras enable users to be more productive, reduce operation costs, and receive more value for their investment.