 Figure 1: Workflow and products of the photogrammetric/remote sensing process 3. Relevant satellite sensors and new aerial digital cameras The development and increased availability of highresolution, multispectral and stereo-capable satellite sensors and of a new generation of digital large format aerial cameras is very crucial for the efficient modeling of large sites. Table 1 shows an overview of highresolution satellite sensors (including medium resolution ASTER because of its good availablity and low costs), which might be useful in cultural heritage applications. There is a great variety of image products available in terms of geometrical resolution (footprint), spectral resolution (number of spectral channels) and costs. All images of Table 1 are acquired with digital sensors, using Linear Array CCD camera technology. For precise processing this requires a particular sensor model and the related special software There are and have been also a number of film-based photographic satellite cameras in use (Jacobsen et al., 1999). This includes the US Corona satellite (2-3 m footprint, B/W, stereo, US$ 24 for a scanned image). The availability of images and the costs can be checked through a number of image providers over the Internet (see Table 1). It is very important to select the right product for a particular task. Table 1: Main characteristics of high and medium resolution pushbroom sensors carried on satellites. L = along-track; C = across-track, PAN = panchromatic, MS = multispectral   The new generation of sensors have a number of particular properties which require new approaches in processing, if the inherent accuracy potential shall be used. Images from CCD sensors do have a much larger dynaminc range than film-based images, so there is more detailed radiometric information present in those images. This is important in particular in areas of shadows and areas close to saturation. Linear Array sensor do have almost parallel projection in flight direction, which leads to less occlusions and gives better orthoimage products. Linear Array imagery, if acquired in multi-image mode, e.g. by Three-Line-Scanners or Multi-Line-Scanners, has 100% overlap for all strip images over the same area. This delivers better precision and reliability of results. Finally, Linear Array imaging systems are using GPS/INS sensors for position and attitude determination of the imaging sensor, which can be used advantageously at different stages of the processing chain. Taking into consideration these facts and other parameters and constraints, we have developed some new methods and the related software packages for the high accuracy processing of aerial and satellite Linear Array images. For the aerial case we have developed a complete software system in cooperation with Starlabo Inc., Tokyo, the manufacturer of the Three-Line Scanner STARIMGER, consisting of the following modules: + TLS-SMS: Userinterface Image measurement in mono and stereo 3-ray forward intersection (point positioning) Image and shadow enhancement + TLS-IRS: Quasi-epipolar rectification to plane or via DTM/DSM Orthoimage generation + TLS-LAB: Sensor/trajectory modeling, georeferencing/triangulation Automatic and semi-automatic tiepoint generation + TLS-IMS: Image matching for DSM/DTM generation DSM/DTM modeling and interpolation + Feature/object extraction, e.g. city modeling: CC-Modeler, CC-TLSAutotext This software can also be used for other Linear Array aerial camera systems and for single farme systems. For instance we have applied it already to ADS40, DMC and Vexcel UltraCam images. For the satellite image case we have developed a modified version of this software, called SAT-PP (Satellite Image Precision Processing), with similar functionality as described before. The key difference to the aerial case is the use of other sensor and trajectory models. In recent years we have done a number of experiments and tests with TLS/STARIMAGER aerial images (Gruen and Zhang, 2003a, Zhang and Gruen, 2004) and with satellite stereo images from SPOT (Poli et al., 2004), IKONOS and Quickbird (Gruen and Zhang, 2003b, Eisenbeis et al., 2004, Gruen, et al., 2005) with respect to georeferencing (orientation), measurement accuracy (point positioning), Digital Surface Model (DSM) determination and orthoimage generation. These investigations have shown that with the proper methodology and software one can achieve extraordinary results. Both with aerial and satellite images one can get a georeferencing accuracy of better than 1 pixel. In automated DSM generation one can achieve a height accuracy of 1 to 5 pixels, depending one many factors like surface roughness (flat and smooth or mountainous areas), landuse parameters (forest, desert, urban areas), local texture (sand, snow), time and month of image taking, etc. Accurate DSM/DTM data is not only an important product in its own right but is also necessary for the derivation of good quality orthoimages. 5. Status of automated processing The automation of photogrammetric processing is obviously an important factor when it comes to efficiency and costs of data processing. The success of automation in image analysis depends on many factors and is a hot topic in research. Progress is slow and the acceptance of results depend on the quality specifications of the user. Also, the image scale plays an important role in automation. Potentially, the smaller the scale the more successful automation will be. Therefore it is a bit difficult to make firm statements which would be valid in all cases. However, in general one can state that
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