I started using IDRISI to process imagery and continued to use it as Clark Labs at Clark University contuied to develop the software. They required a per seat license fee but it was not expense when compared to other remote sensing software . In January 2025, they updated the software to an open source format and removed fees for download and use.
TerrSet (formerly IDRISI) is an integrated geographic information system (GIS) and remote sensing software developed by Clark Labs at Clark University for the analysis and display of digital geospatial information. This grid-based system allows users to analyze images for effective and responsible decision making for management and resource development and allocation. See https://www.clarku.edu/centers/geospatial-analytics/terrset/ for download.
Download and install with tutorials. Use the tutorials to come up to speed using Terrset. It has a steep learning curve but the tutorials with practice data sets and Youtube videos will help speed the learning process.