When dealing with various data sources and files you must always make sure your data is compatible. So all the units should be the same and your coordinate and projection systems should be the same across all files as well. This makes sure that once your various layers and data files are collected into one map the entire collection works together to make a concise and legible map that serves its defined purpose. The following steps are necessary to ensure this happens. First you would check to make sure all the data files were on the same coordinate systems/ projections. If not you must make them so. Next you would make sure all units were matching, ie all in meters or all in kilometers for linear data, all degrees for angular data etc.

Remotely sensed landsat data is extremely useful for geographic analysis. It allows one to view a large area at once. It also contains various color layers that can be adjusted to highlight different changes in the landscape. The timescales of landsat data is also useful. Since the seventies lansat data has been collected in steady intervals. This allows us to see the change in landscapes over short time scales as well as long scales.