Q: The camera is equipped with a 16 bit CCD sensor. Will this sensor enable us to use the camera in marginal weather, also for orthophoto production? In vector map production, the critical factor regarding image quality is if you can see the objects, but for orthophoto colours are important.
A: Yes, it is not only possible, but slight homogeneous cloud coverage sometimes is even an advantage, since shadows are less prominent. Therefore the camera system is usable under marginal weather conditions, as long as during the flight a mostly homogeneous cloud cover exists over the area. Exceptionally low light levels can be accounted for by longer exposure time and slower flying speed. On such occasions it is possible to start flying earlier (lower sun) by 1-2 hours, and stay longer in the air in the afternoon about the same time.
All CCD lines feature the same high sensitivity therefore you can acquire coloured orthophotos in marginal weather.
Q: It is claimed that the accuracy of matching is better in images from a digital camera or scanner compared to a scanned film image. Please explain how much better the matching of tie points for aero triangulation is on the digital images.
A: The accuracy of the matching is in the range of the pixel size with full compensation to pixel accuracy of the influence of roll, yaw, and pitch. While photo scans have a typical resolution of 15µm, our camera yields 6.5µm, so we can provide more than twice the overall resolution at the same exposure conditions.
Q: Digital images are acquired and stored in the mass memory during flight. It is possible to have a look on the image material during data acquisition? It should be possible to access the image material to make a first rough quality assessment of the image data and to ensure full coverage of the mission area.
A: An important point of our quality control "in air" is the limited "Online Quicklook" Software. With this software we can check the raw data. With this validation tool you can check all sensors, the header data the histogram.
Q: Is your scanner depending upon pan-sharpening to produce a high resolution colour composite image?
A: The camera can be run with full pixel resolution for the colours. Then no pansharpening is necessary. Sometimes, in order to reduce data rates and volumes, the colour channel binning may be commanded.
Q: Please explain how much better DTM correlation is compared to film cameras. In relation to the DTM correlation, please describe how the use of multi image matching in DTM correlation will produce a Digital Surface Model (DSM) without blunders. By DSM we mean a model that conforms to the top of the measured objects in the scene, and not edited to terrain level.
A: Use of multi-image matching from five stereo swaths ("Quintuple Stereo") produces a denser matching and enables a far better detection and removal of errors that leads to less editing time. Up to 200 times a second absolute location information is recorded.
Q: Is it possible to exchange the lenses of the JAS 150?
A: Due to the design of digital cameras it is not possible to exchange just the lenses.
Q: Is an inner orientation necessary with the JAS images?
A: No, data is acquired digitally with precalibrated CCD lines.
Q: For flight planning I would like to know the analogous focal length of the JAS 150
A: The focal length of the JAS 150 is analogous to a 442mm focal length of traditional film cameras with a 23cm (9inch) image format. To acquire an image with a comparable pixel size to a 20µm scanned image flying higher is recommended. For example flying at 3000m could give a similar resolution to a 150mm focal length film camera flown at 1000m. The swath width with the JAS 150 would be 1600m. The ground sample distance (GSD) would be 15cm for images from both cameras.
