A Scalable Terrain Model (STM) is a new object type designed to provide high speed display of very large digital terrain models. The STM is created from a variety of elevation data sources including XYZ files, DEMs, breaklines and others. The STM system keeps track of the files that make up a STM. If changes are made to the source files, running the “Check if up-to-date” function will notify the user that the STM needs to be updated.