As learning path 3.20 already introduces you to the concept of change detection, it must be noted that such process is susceptible to certain uncertainities and errors with regards to the fact that changes in the observation system can be confused with the actual changes in the target objects themselves.
This learning paths, therefre, seeks to focus on specific changes involve in change detection process. The first element for dicussion in this path is the term Observable.
The next line for our discussion in this learning path is on true and apparent changes -- as these changes can be mistaken for the each other in change detection process.
Having looked at the specific changes in change detection as a process, it is worth considering also reflecting on the techniques in change detection as already elaborated in learning path 3.20.