Change is inevitable. Harnessing that change has advantages, especially with tools that can detect and anticipate it. At the National Geospatial-Intelligence Agency, change detection plays an important role in helping analysts carry out the agency’s various missions. Change detection is used at NGA to support military customers, but it is also a useful tool for farmers, foresters and government agencies. It can also help predict natural disasters such landslides before they occur. 

From a geography standpoint, change takes place on the planet’s surface as a result of climate, geological events and human-made activities. Observing that change and comparing the before and after to easily reach an analytic assessment or accurate prediction has long been a goal of scientists, government agencies, the military and industry.

Change detection, from a foundation GEOINT perspective, is the process of measuring the attributes of particular geographic areas that have altered between two or more time periods. It is the comparison of multiple images collected for one area at different times, to determine the type, magnitude and location of change. The analysis is derived from either aerial or satellite imagery.

Refined Persistent-Change Model Insights pixels are areas in an image that most likely show changes between two time periods. The presence of RPMI pixels cue cartographers to an area that changes have likely occurred there. Note that the absence of RPMI detections should not be taken as evidence that there wasn’t change. For example, RPMI detects about a quarter of new road construction.

Another use for RPMI data involves accelerating broad area searches. For example, if an analyst has public information or news that a facility was constructed somewhere in a large swath of territory, they may focus on places where RPMI has detected change.

Paired with accurate, up-to-date maps, change detection can play a vital role in monitoring other conditions around the world.  The forestry industry and the U.S. Forest Service use this technology to monitor deforestation and tree health.  Geologists use change detection tools paired with geological datasets to manage geohazard risks and to plan mitigation efforts. Those inventories might include the location, size, type and other information regarding landslide, rockfall and subsidence hazards.  Natural resource managers use change detection to manage protected areas including those that are habitats for endangered species.

Article by James Brown, NGA Communications