Convert2geo - Interpolation

In this tutorial is supposed that a geometry in the geo format was created in accordance with the previous tutorial. If yes, the another step is to generate a mesh inside of the geometry by a native mesh generator of the GMSH software.

The mesh model respective their levels (top, bottom, middle) are flat and there is no information about the feature of the levels. In the case a feature of the model should be shown, a data transformation has to be done which describes this part of tutorial. Whole process includes a few data transformation steps like a msh->dbf, dbf->msh conversion or a data processing in the GIS (interpolation, convert feature to 3D, etc.).

Transformation of elevation level data from MSH to DBF file format

In the same time can be transformed only one level of the model. In the case that more levels are needed to transform, whole process would has to be executed more times. The transformation can be performed by the Convert2geo, there is a tab “Mesh interpolation” in the software, that can convert a level data from msh to dbf file. In the GUI of the Mesh Interpolation software is required to insert the path of the msh file as an input and a dbf file as an output. As well there is reqiured to fill in a number value of the level that should be transformed.

Transformation process by the ArcGIS

This chapter includes 7 steps, which are connected together and is important to do all of them in the order.

• 1. First step is to import a dbf data into ArcGIS as a shapefile, because only the dbf file is not enough for another GIS processing. The dbf file includes four coloumns (ID, X, Y, Z). So the way how to create a point shapefile is to use the X and Y coordinations. For this purpose can be used the tool Add XY Data, which is in the main menu under tools item.

• 1. Further should be prepared a digital terrain model (DTM) or contour lines layer, which is a 3D representation of a terrain surface.

• 1. In this step is needed to convert the point shapefile layer from 2D to 3D form by the Feature to 3D tool in the 3D Analyst toolbox. In this tool is required to fill in the path to DTM layer that was prepared in the step "2.".

  2. The 3D point layer can be used to creation of a Z coordinate. The tool that performs the creation of the Z coordinate is called Add XY Coordinates.

• 1. Further is required to copy the ID attribute from the original shapefile layer into the new layer that was created in the step "3.". It is because in the newer 3D converted layer is not the ID attribute with values from the msh file. The way how to copy a data between two tables is to join both tables and perform the copy by the Field Calculator.

• 1. The last step of the ArcGIS processing is to export of the data. There is possible to use the tool Export Feature Attribute To Ascii in the ArcToolbox that allows to export the shapefile data into csv format.

Transformation of elevation level data from DBF back to MSH file format

Now we can proceed to the move of the data back into the original msh file. The Convert2geo is the software which allows to transform a data from dbf back to msh file. The process is similar like in the chapter 2., but now has to be chosen the option DBF->Mesh and the path of the input file should be changed as it was exported from ArcGIS.