You have an orthophoto and elevation model available from your photogrammetry process and want to get them in Virtual Surveyor. You have to create a terrain.
TerrainCreator converts your orthophoto and elevation model into an interactive 3D terrain.
The following steps describe the process:
- Launch TerrainCreator
- Define the 'Output project file'
- Define input files
- Optionally: adjust 'Projection system' and 'Ignore value'
- Click the 'Create terrain' button
- To start TerrainCreator click on File > New > Create Terrain
In the TerrainCreator window click on the top folder icon to specify your 'Virtual Surveyor project file' name and its location.
- In 'Input image information' select your orthophoto and in 'Input elevation information' select your digital elevation model (dem, dsm). They can consist of one large file or a set of data tiles that together cover your entire project area. For more information on the input files take a look: Requirements for input files when creating a terrain.
If needed, specify the 'Projection system' for your image and elevation. Usually your projection information is available with your GeoTiff file and is filled automatically. If your metadata does not contain projection information, it can be defined manually. For more information see Manually define projection information.
In case 'NoData' is not available or not set correctly modify the 'Ignore value' field (=NoData).
This parameter is used for pixels with unknown elevation. This is often a very low value that falls outside the range of the realistic elevation values. Typical values are -32767 or -99999, athough any other number could have been used here.
When all the required inputs are available, teh 'Create terrain' button is enanble. Press the button to start the creation process. The progress bar and the remaining time will be displayed at the bottom of the window.
- When the terrain creation process completes, your project is opened automatically.
The setting 'Background value' is defined automatically. You can manually modify this value, though we recommend to keep the default value, as it is optimized for your terrain. It is set to a value at the bottom of your elevation grid, rounded down to the next ten.
It is important that the background value lies close to the minimum elevation, otherwise it will be difficult to navigate through the new terrain. This principle is illustrated in the figure below. Suppose the bottom of a valley lies at 100 m and the original 'Ignore value' of the elevation model is 0. A 'Background value' that is too low, will result in the 'Tower-effect' in the terrain (a). This effect makes it difficult to navigate smoothly through the terrain. When the 'Background value' is applied correctly (i.e. a value close to the minimum elevation), the resulting terrain file will look like (b), with a flat plane surrounding your area making it easy to navigate around.