Scene Analysis Districts
lCan be defined by
–Contiguous same date coverage
–Scene edge or county boundary
lCloud free or near
–    cloud free dates
lUnitemporal
–One date
lMulti-temporal
–Two date(s) overlay
•Analysis Districts (AD) can be a individual or multiple scenes footprints that have to be observed on the same date, and analyzed as one.  An AD can be comprised of one or more scenes. An AD can be defined by either a scene edge or a county boundary.  Multi-temporal AD's are possible as long as both dates in all scenes are the same.
•A single or multi-scene AD will use all potential training fields for clustering/classification/estimation. Even though a segment can lie in more than one scene, each segment can be identified as belonging to only one AD.  Therefore, a segment can be used many times during the clustering/classification stage, depending on the amount of scene overlap, but each segment can be used only once for estimation.
•Preliminary definition of AD’s usually only considers the dates of imagery and the existence of cloud cover problems. A slight re-definition might later be based on amount of training data available or parameters required in the regression estimation process.
•Usually all parts of an AD are contiguous, but “holes” might exist due to cloud cover problems.
•Having two dates per scene location is preferred, one early in the growing season of the most important crops and one later. For example, in the Mississippi River Delta Region, one scene from April through May, and another from June through August would be selected; these cover the spring planted crops such as rice, cotton, soybeans, corn and sorghum.
•Two scene dates from the same sensor and same scene location can be overlaid; in addition, Landsat 5 TM and Landsat 7 ETM+ can be overlaid with each other.
•If only one date can be found for a given scene location, it would be selected based on the mid-growing season of the most important crops. Anytime the vegetation of interest is active and not in senescence, may work.
•In a two date image situation, some information is usually gained from scenes that are too early, such as the distinction between woods/pasture and bare soil.
•In a one date situation, scenes that are too late tend to create confusion due to bare soil, harvested crops, or non-vigorous vegetation. Obviously, scenes that are too early have bare soil for crops.