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Navigation: Using CatchmentSIM's Algorithms

Setting Up a New Project

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The first stage in development of a CatchmentSIM project is to set the projection and project boundaries.  


Project Projection


The project projection is selected from a drop down box on the New Project form. No single projection can be recommended for all applications and the appropriate projection should be based on many factors including size of the catchment, geographic alignment of the catchment and objectives of the analysis. Conformal projections conserve angles while Equal-Area projections conserve areas. For catchment studies, Equal-Area projections may be more appropriate. CatchmentSIM includes the Albers Equal Area Conic projection which can be used to conserve area measurements.


You do not need to work in the same projection as your data. CatchmentSIM supports re-projection of both vector and raster data sources upon importing the data provided the transformation is supported by CatchmentSIM (You will be advised of an unsupported projection if you select it). For large projects, you can also work in latitude and longitude. However, this will disable the length and area calculations since the raster grid will not have a constant pixel size. To overcome this you can export your subsequent subcatchment boundaries after processing and analyse them in other GIS software.


Project Boundaries


The project boundaries should be large enough to accommodate the catchment of interest but should not be excessively large and include a large amount of redundant topography. The project boundaries are used to trim all data that is imported into the project. This allows the use of large GIS data sets as input data for a project. For example, after a user sets appropriate project boundaries which are large enough to contain the catchment under analysis, they may then assign a very large GIS database as the project source data. CatchmentSIM will only import and store the digital terrain information that is within the project boundaries. Contour or stream lines that cross project boundaries are clipped at their point of intersection. Consequently, the same source database may be used for many projects without manipulating the data with the parent GIS application. In fact, it is not necessary to own any commercial GIS software, merely, to have access to the appropriate database in an accepted format. CatchmentSIM provides all the tools required for basic data manipulation including addition / deletion of contours and watercourse data.


After defining the project boundaries through the CatchmentSIM Drop Down >> New Project menu option, the project boundaries can be modified using the CatchmentSIM Drop Down >> Project Properties menu option. For example, if after delineating your catchment boundary you find that the project boundaries are not sufficiently large to fully contain all of the catchment, you can increase the project boundaries through the CatchmentSIM Drop Down >> Project Properties menu.