Having good DEMs is critical for effective change detection. In this series of video tutorials, we lay out how to build DEMs from raw topographic data (e.g. rtkGPS or total station data). A similar procedure is available for airborne LiDaR data here. OverviewIn this tutorial we are provided with some raw topographic survey data. Your job is to build a DEM from that data (of appropriate resolution), show the water depth overlaid on the DEM, and pull a longitudinal profile and some cross sections off the DEM. You will use a triangular irregular network (TIN) to interpolate between your raw topographic survey data and produce a continuous surface that you will later convert to a raster DEM.NOTE: These instructions are for ArcGIS 10 and are primarily provided in the form of video tutorials. As an additional reference, you might find the 'Using ArcGIS 9.3.X to Construct and Manipulate DEMs' tutorial listed in the main Lab 6 page helpful (it uses different data, and is for the old version of ArcGIS, but goes through a similar sequence of steps to arrive at the same end point in Part I of the document; one significant difference is the absence of TIN editing in ArcGIS 9.3.X). DataEverything you need to create a TIN can be found in thePatsCabinSurveyPoints.csv file and the Task3_PatsCabinShapefiles.zip ![]() Although not covered in the video tutorial, I would suggest exporting the PatsCabinSurveyPoints.csv table you imported as X-Y points to a shapefile or feature class to use in the construction of the TIN (I named mine TopoSurveyPoints ).Building TINSYour First TINIn this video tutorial, we go through the simplest form of constructing a TIN from just raw topographic survey point data. We also highlight some of the potential pitfalls to this approach.A Better TINIn this video tutorial, we talk about how you can build a TIN using a polygon hardclip boundary as well as how to manually edit your tin with the TIN Editing Tools.A Better TIN yetIn this video tutorial, we will use the same data used in our first two TINs as well as the some 3D breakline data provided to you:Building DEMBuilding the DEM is a simple matter of converting the TIN to a Raster. This video tutorial walks you through the considerations.For this exercise, we have not been careful with the creation of this raster (see best practices for a follow up). OPTIONAL: Building Water Depth DEMSince we have a DEM that includes shots above the water and below the water, and because the survey data denoted where the water's edge shots are, we can derive a bathymetric water depth DEM. The way in which we will do this is to:
OPTIONAL: Pulling Some Cross Sections and a Long Profile Off DEMUsing
the 3D Analyst interpolate line and profile graph features, you can
easily pull off a longitudinal profile and cross section(s) from the
DEM. This video shows you how:ReferencesThe above exercise comes from a Lab in my Advanced GIS Class. If you want more information on how to work with DEMs and topographic data, you may find Labs 6, 7 and 8 helpful references/refreshers. |