You want to understand the purpose of the files generated when you created a new terrain in Virtual Surveyor. You want to know the difference between project and terrain files.


Short overview


Files produced by TerrainCreator


When you are creating an interactive 3D terrain, TerrainCreator produces a Virtual Surveyor Project file (*.vsp) and a sub-folder with six files in it. 


The project name, sub-folder and all the files within have the same nameThe location of the sub-folder relative to the Virtual Surveyor project plays an important role. You can find more details in the solution on How to make a project portable.



The sub-folder contains *.mpt, *.mldx and *.Stri files. There are two files of each format: one for the image (.ii.) and one for the elevation terrain (.ei.):

  • Terrain file format *.mpt is meant for fast and smooth visualization in 3D. TerrainCreator generates *.mpt files based on your input orthophoto and elevation model.

  • *.mldx and *.Strmi are supporting file formats. These files should not be moved or deleted.



*.vsp is Virtual Surveyor Project file. It is a container file that initially only includes links to your terrain files (*.mpt), that is why it is only a few kilobytes in size initially. When you start working this will change and project file size can go up to many megabytes, for example, when you have dense point grids. 


Besides the initial links to the terrain files, Virtual Surveyor Project files (.*vsp) can include the following:

  • survey objects (points and point grids, polylines, polygons, and TIN's)
  • links to 3D models, pictures, feature layers, other terrains and point clouds
  • a terrain map and other objects created using Analysis > Terrain Analysis functionality
  • camera locations and storyboards created using Presentation > Design Movie 
  • other information such as annotations, label text, results of volume calculations etc.


Files produced while working with a project


The moment you save changes to your project a backup project file is created (*.vsp.backup). Initially it contains the links to the terrain files and this file is updated every time you save new changes to your project. Backup file preserves the state of your project the way it was the previous time this project was saved, which allows you to reconstruct the project in case of a crash.


If you save a Virtual Surveyor project under a different name (File > Save As) you create a new *.vsp file, but the name of the sub-folder with terrain files will not change. All versions of the project will be linked to the same terrain files. For example, you can have three versions of your project: MyVirtualSurvey.vsp, MyVirtualSurvey_version2.vsp, and MyVirtualSurvey_version3.vsp, but only one sub-folder with terrain files. It will be called MyVirtualSurvey, like the initial project generated using TerrainCreator



Note: *.fly is an old format of a project file. Virtual Surveyor still supports *.fly files. To open such file go to File > Open > Browse and change the default file type in the Open window to *.fly