Metadata
Metadata about imagery is important to maintain. Unfortunately, there are few standards to which are adhered. Typically, imagery that comes from a major data provider comes with associated metadata files for each scene. When there are a large number of files associated with a single project, such as an aerial survey mission or a large collection of tiled images that make up a dataset, then metadata may be available in the form of a table, or metadata is only associated using a document stored with the files.
It is recommended that any metadata that comes with the imagery be stored alongside the imagery. If a mosaic dataset is created from the imagery, then the appropriate metadata should be either directly ingested as part of the raster type used to ingest the data, or added as additional fields to the mosaic dataset. The schema for additional fields in a mosaic dataset is not enforced; therefore, fields with any valid name or type can be added. Attribute fields are copied from a source mosaic dataset to derived mosaic datasets, so standardizing on the field naming of the source mosaic datasets will reduce the presence of empty attributes in the derived mosaic datasets. The following is a list of some proposed field names for commonly used metadata fields.
- AcquisitonDate[Date]
- CloudCover[Long]—(0 – 100%)
- NadirAngle[Long]—(0 – 90 deg) 0 is vertical
- LE90 [Float]—Horizontal Accuracy
- CE90 [Float]—Vertical Accuracy
Each workflow will make additional recommendations.