Description of TBGIS functions

Generation DEM from various sources

DEM can be generated with the data in following format: Following interpolation options are provided:

DEM quality examination

DEM is the basis of all the spatial analysis followed. Due to the diversity of data sources, lack of proper metadata, scales, as well as interpolation technique involved, proper assessment of DEM quality become a necessity for any terrain-based modelling.
Four methods are designed to aid user to examine the quality of a DEM generated.

Calculation of terrain-controlled erosion potential


Estimation of process-based erosion potential is carried out by:

Estimation of relative erosion and deposition


Neighbourhood function in Arc/Info Grid is used to identify the neighbour cells of a processing cell. Erosion potential of the central cell is taken as the actual sediment output and erosion potentials of neighbour cells are taken as the possible inputs. Based on the principle of mass conservation and assumption of transport-limited condition, the difference between input and output is regard as the relative erosion and deposition value for the processing cell. Three mechanism are available to decide the actual input from neighbour cells.
D8 method
This method is based on the flow direction given by Arc/Info GRID. It means that the sediment of a cell can only be moved to one of its eight neighbour cells. This method is used in EROS of TAPES-G.
Slope method
This method defines relative erosion and deposition value as the change of erosion potential along the flow path. Aspect is used as the indication of flow direction. A simple differential mechanism is used to derive the change of erosion potential along the X-axis and Y-axis direction. This method was originally proposed by Mitasova and applied on the GRASS GIS
Multiple paths method
This method is based on the relative heights among neighbour cells and processing cell. Erosion potential of a cell become the input of all neighbour cells which has lower heights. The gradient between processing cell and a neighbour cell determined the proportion of erosion potential this neighbour cell will receive.

Transformation of relative erosion and deposition to caesium-137 inventory at sampling time


For most of the cases, you do not have to use this function unless you are really keen on the combination of erosion and deposition modeling with caesium-137 techniques.
Caesium-137 inventory has been shown to be a good indicator of net erosion and deposition patterns. For validating the prediction of erosion and deposition patterns from TBGIS, it is necessary to calibrate the relative erosion and deposition values to caesium-137 inventory at sampling time. Dr Qingping He's method is implemented for this purpose. A station file containing the actual or relative annual air deposition of caesium-137, local reference caesium-137 inventory, avearge tillage depth are required for this operation.

Data manipulation, analysis, visualization, and export


Terrain modeling is a multiple-step, iteriative processes. Tools are provided for manipulating, viewing, analysing, and exporting original data, intermediate results, final results.
Geo-data generation: Tools are available to generate info file from a plain ASCII file; generate point, line, or single polygon coverage from plain ASCII file; and convert TIN to a grid.
Geo-data management:
Geo-data analysis:
Geo-data export: