In reality, photogrammetrists started to introduce the use of digital imagery where it benefited the workflow most. At this point in time photogrammetry was mostly driven by the exciting and challenging task of developing digital image processing techniques to solve basic problems in aerial images, which have a very high and complex degree of information. The special challenge for the third generation of photogrammetry is to replace existing workflow steps and become more productive. Doing this does not involve developing completely new applications, but creating a smooth transition of a complete production process of precision mapping into a promising world of new possibilities and efficiency. The main problem is still challenging - to model our world, to automatically gather the exact required information, to offer the shortest possible production cycles and to offer new value from digital images.
For this reason, it is no surprise that the field of photogrammetry is still playing catch-up, and being thrust into the realm of digital acquisition. Small format digital frame cameras have been around for a few years, and are becoming widespread, although few are for sale commercially. Recently, two major vendors in the photogrammetry market have announced their entry into the multi-scale production quality digital mapping camera market. These two cameras, with radically different designs, will finally close up the digital imaging technology gap in photogrammetry.
The new direct digital data acquisition is able to provide image data just a few hours after the mission was flown. Typically Post Processing takes just a few minutes per image shot. Depending on the mission size the data can be available one day after the images were taken. Another superior advantage over the traditional wet film, is the
ability to assess the quality of data taken directly after the flight is done.
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But how can airborne digital cameras improve digital photogrammetry? Most obvious of course are the following points:
- Direct digital aerial data acquisition dramatically reduces access time to imagery
- Multi-spectral data can be taken simultaneously with high resolution images
- Digital sensors offer expanded operating times and flexibility over film cameras
- Improved quality of imagery and derived products
Presently photogrammetry often lacks in supplying information on a very short schedule. This is because film has to be developed and scanned before being available for further processing or compilation. Normally this delay is up to 5-9 days, depending on the project size. The new direct digital data acquisition is able to provide image data just a few hours after the mission was flown. Typically Post Processing takes just a few minutes per image shot. Depending on the mission size the data can be available one day after the images were taken. Another superior advantage over the traditional wet film, is the ability to assess the quality of data taken directly after the flight is done.
Conventionally multi-spectral data can either be accessed at low resolutions from satellite, which offers about 1m ground sampling distance, or be taken by additional photo flights if higher resolution is required. As new digital cameras are equipped with near infrared sensors, this information is captured simultaneously with high resolution panchromatic imagery. In the future panchromatic, color or color infrared images can be generated from one data set.
A photo flight does not always have to deliver images at ideal illumination, so that the user can produce the best orthophoto quality. Most missions for pure mapping purpose can make use of expanded operating times. The high dynamic range of CCDs, combined with time delayed integration (TDI) supports flights when very long exposure times are required. The user may benefit from 12 bit dynamic range which allows lightening of shadow areas as well as visualization of texture in very bright areas.
