Elevation profiler (see Krebs et al. 2015) is an open source GIS tool designed to work with ArcGIS that automatically calculates transverse or longitudinal elevation profiles of different lengths starting from a digital elevation model (e.g. high resolution Lidar DEM) and a shapefile of points (i.e. the midpoints of the profile segments). The calculated profiles are then saved in comma-separated tabular data files (.csv).
An elevation profile represents the intersection of a vertical plane with the DEM surface. In particular, the Transverse Elevation Profile (TEP) is defined as a two-dimensional cross sectional profile in the vertical plane oriented perpendicularly to the maximum gradient direction, while the Longitudinal Elevation Profile (LEP) is a profile following the line of maximum slope (see Krebs et al. 2015). These elevation profiles provide a real-scale visualization of the relief of the terrain and offer multiple possibilities for analyzing the topography and the terrain curvature around spatial points.
At the moment (September 2015), the tool is available in the following two variants:
- VBA for ArcGIS 9.3 (and previous). Originally the Elevation profiler was conceived as a VBA (Visual Basic for Applications) macro ready to be added and run from the visual basic editor in ArcGIS 9.3 and previous versions. This first version is composed by a form interface and five modules. The code is found in the vba_for_arcgis9 folder.
- Add-in for ArcGIS 10.0 (and higher). Starting at version 10, VBA is no longer supported in ArcGIS and a special license is required to open the VBA editor and to use any macro or customization built with this code. To overcome this problem, the Elevation profiler GIS tool has been migrated to Visual Basic .NET (VB.NET) and is now provided as an add-in for ArcGIS. The code is found in the addin folder.
Through a simple form interface the user can choose some parameters that define the characteristics of the required profiles. At first the user has to decide which type of profile (TEP or LEP) he want to obtain. Then with the minimum length, the maximum length and the interval the user decides the list of increasing lengths of the profiles he wants to obtain for each point or site. The level of accuracy adopted for the procedure of orientation of the elevation profile can be controlled by changing the number of circle points. This parameter directly affects the time required for calculations. The resolution defines the number of points that will be created on the profile segments. For instance with a resolution of 1 meter a 100 meters long elevation profile will be composed by 101 segment points. The resolution has to be set by considering the cell size, or spatial resolution, of the DEM raster.
Starting from the point features defined in the shapefile, and retaining these features as centers of the profile segments, the tool builds an elevation profile around every point. As first step the tool creates a horizontal circle centered on the site with a diameter equal to the desired profile segment length. The orientation of the TEP is given by the pairs of opposed circle points that minimize the absolute difference of altitude when projected on the DEM. On the contrary, the pairs of opposed circle points maximizing the absolute difference of altitude defines the orientation of the LEP. Thanks to this particular procedure, the resulting directions of the longitudinal and transverse profile segments will respect the average aspect of the slope, without depending only on the local maximum gradient direction measured at the site. Then for every segment point the Elevation profiler extracts the value of the altitude from the DEM by applying a bilinear interpolation. At the end the GIS tool saves all the results in various types of comma-separated tabular data files (.csv). In particular the elevation profiles for every site are saved as columns in a table with a row for every segment point containing the difference of altitude as regards the elevation of the site. The orientation of every profile segment and the spatial coordinates (X e Y) for all segment points are saved in two additional .csv tables.
- Krebs, Patrik; Stocker, Markus; Pezzatti, Gianni Boris; Conedera, Marco; 2015. An alternative approach to transverse and profile terrain curvature. International Journal of Geographical Information Science, 29(5), pp. 643-666.
- Patrik Krebs (patrik.krebs@wsl.ch) and Gianni Boris Pezzatti (boris.pezzatti@wsl.ch): Insubric Ecosystems Group, Swiss Federal Research Institute WSL, Bellinzona, Switzerland.
- Markus Stocker (markus.stocker@gmail.com): Research Group of Environmental Informatics, University of Eastern Finland, Kuopio, Finland.