The differences can now be standardize using the overall standard deviation: These can be used for mapping of channel net- works and watersheds. Land-cover classification and estimation of terrain attributes using synthetic aperture radar. A digital image processing approach to creating dtms from digitized contours. Information on contours can also be used to estimate the accuracy of elevation measure- ments RMSE z and suitable vertical precision of a DEM.
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For regional and national level studies, a high resolution DEM is unrealistic. Computer Vision, Graphics, and Image Processing, 28 1: Other classes seems to be in general easier to distinguish, although there is obviously overlap between streams-plain and ridges-plain.
Click here to sign up. It will produce a set of equiprobable realistic DEMs, each showing a similar histogram and variogram.
First the DEM map is sliced axademic an equal interval, e. Integrating them in a consistent way and presenting them in a unified to the end users at both programming and user interface level. Rhind, editors, Geographical Information Systems: Another option is to choose the pixel size that ilwis 3.0 academic to the minimum resolution of application, e. The grid resolution of AP is acavemic m. Interpolation between isolines based on the borgefors distance transform.
In the case of elevation, which is often a spatially contiguous variable , spatial variation can be modelled by using an unbounded semivariogram model such as the exponential model: From the above-mentioned techniques, laserscanning seems to be the most accurate method with the highest sampling density.
Each cell receives the value 1 plus the sum of the fractions of eight neighbours: The single flow direction depicts only a main direction of flow run-offwhich may give rise to local inaccuracies. Mitas and Mitasova  compared various interpolation techniques for optimal DTM.
The contour interval is 20 m in hill and 5 m in the plain, hence we used the RMSE z of 5 m in the hilland and 1. The SINS is also derived using the first and second order derivatives : Accuracy of local topographic variables derived from digital elevation ilwis 3.0 academic.
Here, the original elevation is compared with the value estimated from the neighbours: The outlier7s are reduced by calculating a probability to find a certain value within the neighbourhood . Each ilwis 3.0 academic iteration will propagate flow by a distance equal to the pixel size or the di- agonal pixel size. Note that the definition of classes and class centres Fig. Geografiska Annaler, 57A Soil 33.0 Society of America Journal, With the increase of pixel size, spatial prediction will be less discernible, while decreased vertical precision will typically show more erratic values .
Msc thesis, ITC, In the most raster GIS applications flow accumulation algorithms are implemented by directing the flow into the lowest neighbouring cell. Landform classification and soil distribution in hummocky terrain, ilwis 3.0 academic, canada.
Although the gridded DEM-data model is non-adaptive and commonly over-samples in low-relief areas and under- samples in high-relief areas, it is somewhat more attractive than the TIN DEM due to a simple data structure and high possibilities of GIS operations . Consequently, there are four levels of DEM: Springer-Verlag, New York, Another intrinsic property of elevation is its fractal nature.
To review the content of this document, students should ilwis 3.0 academic refer scademic the the following literature: Finally, the specific catchment area Af can be derived as :