This article aims to present the change detection methodology as experienced in the use of optical remote sensing imagery (Landsat) and its pitfalls when multitemporal analyses are performed with ...pixel-based (raster algebra) techniques. The existing methodologyrecommends fundamental data preparation (geometric, radiometric, topographic corrections) and offers numerous change detection techniques. Regardless of the carefully performed preparationscertain noise remains, which can drastically weight the imagery comparisons. This noise behaves as a detected change and could have such a false effect on the identified change pattern (i.e. false, non-intrinsic changes) that the quantitative evaluation might fail.Since this noise originates from the pre-processing algorithms as well as the natural and technological conditions during data acquisition it can not be completely removed by data corrections. A multiresolution change detection approach is therefore proposed. Taking into account the neighbourhood and change information from joining different spatial scales, the multi-resolution approach effectively reduces the amount of false changes. In the discussion the remote sensing imagery for surface change detection is evaluated.
The interactive method of orientation between 2D photographs and a 3D height model presented with a point cloud is described. The orientation parameters of the 2D photograph (rotations and location ...of the camera) are derived using the interactive searching for the best fit of the projected 3D height model points on the image. This method requires good operator’s knowledge of the photograph and its details and above all a lot of time. The most suitable photographs for the interactive method of orientation are the panoramic ones, with removed distortions. On the photograph there should be many easily found targets or details (edges ...). The method was developed for the error search in the laser scanning point cloud (Rönnholm et al., 2003a, 2003b). In this paper a test of the usefulness of the interactive method of orientation on the example of Horizont nonmetric panoramic photographs of the Triglav glacieris presented. Because of the lack of good details seen on the photographs and in the 3D model, we derived only approximate values for the orientation parameters. Unfortunately this is not enough for conducting measurements of height difference out of the Horizontphotograph. If correct values of orientation were available, the height differences between the 3D model and photographs could be measured. This would be done with shifts of the 3D point images on two Horizont photographs, so that they would fit the photographsbetter. The 3D model presents the state of the Triglav glacier in the year 2005. The Horizont photographs present the state of the glacier in each month from 1976 on.
Photoclinometry is a method for extraction digital elevation models from one single image on the basis of shading – in many cases it is also called shapefrom - shading method. The tested program ISIS ...is capable of making interactive photoclinometry. ISIS is developed and used especially for photographs of different space objects. It is an open-source program, which works under the Linux operating system. In this paper, the installation, handling and capabilities of ISIS are described. In detail a module for photoclinometry is described and tested. The test is made on a photograph of a part of planet Mars. The results of photoclinometry depend greatly upon parameters of photoclinomety (albedo and the photometrical function of surface) since a small change of a parameter can cause a big change in the produced DEM. With photoclinometry very accurate DEMs can never be obtained. From the test it can be concluded that results gained with photoclinometry can be used for research or orientation purposes, but never for geodetic precision. One field of possible usage in Slovenia is the old-archive CAS images of snow-covered areas.
Four methods for extracting height data from photographs made with active or passive sensors are described: clinometry, stereometry, interferometry, and polarimetry. Clinometry is described in ...detail. It is a method which extracts height data from just one photograph with the use of the shape-from-shading principle. Digital terrain models of planets Mercury, Venus and Mars and smaller bodies of the Solar system are described. Emphasis is given on the use of the clinometry.
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