Generating a gridded digital terrain model for the surface and loading XYZ topographical data

Product(s): OpenFlows FLOOD
Version(s): 10.02.01.01

Overview

This article will discuss how to import XYZ topographical data into a terrain model.

Make sure to download the associated "Graz" file before starting

Method

The topographic information is essential in order to build the computational mesh with reliable height values in each grid cell. Indeed, this is the basic and most essential information needed to run any MOHID Land simulation.

In OpenFlows FLOOD, we can create topography files based in ESRI shapefiles (using tool “Create Grid Data from Shape”, raster files (using tool “Create Grid Data from Raster”, or in XYZ files (using tool “Create Grid Data from XYZ Points”. In this manual, we will give an example based in the generation of a topography file from XYZ files.

Independently of the type of tool used to create a topography file (Create Grid Data from Raster, from XYZ Points, or from Shape), the following datasets are required to be loaded in OpenFlows FLOOD Map window:

  • Digital terrain data (in XYZ, Shape, or Raster format)
  • The computational grid for the model.
  • (optional) A polygon defining the areas where the model will not calculate any values.

We are creating grid data from XYZ Points, so we will have to load a XYZ topography data file.

We need to load digital terrain data into the workspace, to make it available in the generation of the gridded digital terrain model. Since we are creating a gridded digital terrain model based in XYZ digital terrain data file, we need to load a XYZ file formatted into OpenFlows FLOOD XYZ format. However, the digital terrain data from the XYZ file can be obtained from many different sources (e.g. ETOPO, SRMT, local data provider, ContextCapture).

XYZ Files are used to define a set of points with x, y and z coordinates. These files are typically used to store information from bathymetric or topographic surveys.

XYZ Files are ASCII text file which extension should be *.xyz. XYZ Files contain a set of blocks, each containing a set of point values. One block is delimited by the following case sensitive keywords: <begin_xyz> and <end_xyz>.

A fourth column can be optionally included and it is handled as a character string which can also be used as a legend for each point.

In the following figure, a simple example of a three column OpenFlows FLOOD XYZ ASCII File is illustrated.

Figure 1 – Example of OpenFlows FLOOD XYZ file

In Phase 1 of this guide, a XYZ file named “DTM_xyz.xyz” was already downloaded as part of the “Graz” dataset. We will explain how to copy and import the downloaded file into the directory solution just created:

  • Expand the “Project Tree” and select the folder “Digital Terrain”.

  • After selecting, right-click it and choose “Import File…”, as shown in the next figure.

Figure 2 – Importing external data file to the New Domain

 

Select the correct path for the existing “DTM_xyz.xyz” file extracted from the “Graz” workspace

Add this file to the Map (right-click-> Add to Map…) to visualize it in OpenFlows FLOOD map and use the instructions previously learned in 3.5.2. At the end, you should be able to visualize the following layer:

Figure 3 – Visualizing imported layer in the Map

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