Introduction to ILWIS , using data from Kathmandu, Nepal. 1 The exercises in this chapter are modified from the ILWIS Users Guide, by substituting the. ILWIS Academic: user’s guide. R. Nijmeijer, A. de Haas, R.J.J. Dost, P.E. Budde Place of Publication, Enschede. Publisher, ITC, ILWIS. Publication status. Title, {ILWIS Academic user’s guide}. Publication Type, Book. Year of Publication, Authors, Unit Geo Software Development. Number.

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New methods and tools for grass gis. The fractal property of terrain also means that we can find topography at kilometer, meter suer millimeter scales. Hazards, risk, and maps can be developed and analyzed using the software. In this group, stereo-pairs and criteria-trees can also be found.

The padi terraces are formed when all rays of the interpolation algorithm finds the same contour value in the neighbourhood. This has two implications: The streams are highly concave and ridges highly convex areas. Note that the propagation of the drainage fraction is a time consuming task. Hence, in the case of contour data, the vertical precision can be estimated using: Evaluation on the accuracy of hydrologic data derived from dems of different spatial resolution.

No part of this book may be published, reproduced, or stored in a database or retrieval system, in any form or in any way, either mechanically, electronically, by print, photocopy or any other means, without the prior written permission of the authors.

Sun angle Giide shadow Cast shadow Figure 1. The undefined pixels are replaced by iteratively taking the predominant value from the neighbours.


The vertical precision of the DEM can be compared to the selection of the optimal histogram bin size. In many cases, however, it can be iwlis using a con- tiguous and smooth surface.

Digital Terrain Analysis in ILWIS Lecture notes and user guide | Tomislav Hengl –

Accuracy of local topographic variables derived from digital elevation models. Landform Description SLOPE PLANC SCI Stream Locations of water accumulation channel and transition; high number of min min avg Valley ilwls elements and concave bottom shapes Locations of water run-off; low- Ridge est upstream contributing area and min max min Peak convex shapes Sloping part with generally higher Slope max avg max shape complexity Plain Ter- Flat areas of low relief and low min avg min race shape complexity Pit Conical concave landform avg min min generic landform can be termed: International Journal illwis Geographical Information Systems, 9 4: Extracting topographic terrain features from elevation maps.

Laserscanning has already been applied for mapping buildings, power lines, open pits, surface textures and even waves in the water [69]. Natural Hazards80 169— The artefacts are usser bigger problem for calculation of hydrological parameters.

The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models. This is also referred to as the Monte Carlo method of error propagation [28]. Effect of data source, grid resolution, and flow- routing method on computed topographic attributes. By guise smoothing effect the interpolator can be either exact or approximate and by the proximity effect, it can be either global or local. A DEM implies that elevation is available continuously at each location in the study area.

Hence, the predictions are made by: The averaged elevation will be somewhat smoothed after the filtering for outliers. These would, of course, require somewhat different clustering of attribute space see Fig.


International Journal of Geographical Infor- mation Science, 17 1: Models and Experiments for Quality Handling in…. Quantitative soil-landscape modeling for estimat- ing the areal extent of hydromorphic soils. Showing of 85 references.

Digital Terrain Analysis in ILWIS Lecture notes and user guide

It is derived as the perimeter-to-boundary ratio: In this example Fig. Each cell receives the value 1 plus the sum of the fractions of eight neighbours: This small number used iterations was sufficient, because remaining changes with further iteration were only in stream bottoms, which already had a high CTI relative to other landscape ilwia. The exact weights used for each category can be found in Gaprindashvili and Van Westen In this case N is unknown.

Earth Surface Processes Landforms, The temporary shape map FORM tmp can be extrapolated using the map iterations to fill the undefined pixels: Box 6, AA Enschede, Netherlands. This means that CTI primarily reflects the accumulation processes. However, the selection of the most suitable grid size is not as simple as it seems. Aspect gives azimuth angle of the sloping surface orien- uwer of central pixel. As a result of reduction of errors by propagation, the terrain parameters will be smoother, with much less artefacts and more natural appearance.

The total area is