Updating mosaic datasets with new military data
Data producers, such as the National Geospatial-Intelligence Agency (NGA), that provide data for the defense and intelligence communities, continuously produce new and updated raster products. ArcGIS mosaic datasets help you work with the large volumes of raster data typically associated with these raster products. Once you've added data to a mosaic dataset, it is important to keep the mosaic dataset updated as new data becomes available. This topic describes how to use the Add Rasters To Mosaic Dataset geoprocessing tool to update your military raster data contained in a mosaic dataset.
Mechanism for updating mosaic datasets
The mechanism for updating mosaic datasets is provided by the Add New Datasets Only parameter on the Add Rasters To Mosaic Dataset geoprocessing tool. When you configure the tool for execution, you decide if you want the tool to allow duplicates, exclude duplicates, or overwrite duplicates.
When you add military products such as CADRG/ECRG, CIB, and DTED, which are used to provide basemap data (DTED can also be used for analysis), you should typically decide to overwrite duplicates. When you add NITF data, which is used for intelligence analysis, base your decision on how you plan to use the data after it has been added to a mosaic dataset. For example, if you want to perform temporal analysis, such as change detection, you would want to allow duplicates so that the mosaic dataset referenced rasters that were captured over a period of time.
How are duplicates identified?
The logic used to determine whether or not a raster dataset being added to a mosaic dataset is a duplicate is based on which raster type you selected in the Add Rasters To Mosaic Dataset geoprocessing tool when you added the data to the mosaic dataset.
Raster Dataset and NITF raster types
If you select the Raster Dataset or the NITF raster type when you add data to the mosaic dataset, then the raster dataset being added is determined to be a duplicate if the mosaic dataset already contains a raster dataset that has the same source path and file name.
CADRG/ECRG, CIB, and DTED raster types
If you select the CADRG/ECRG, CIB, or DTED raster type when you add data to the mosaic dataset, then the raster dataset being added is determined to be a duplicate if the mosaic dataset already contains a raster dataset of the same product type (for example, Global Navigation Chart or Operational Navigation Chart) and represents the same geographic area.
Which raster dataset is overwritten?
Typically, when you choose to overwrite a duplicate, the existing raster dataset is replaced with the one you specified you want to add. However, in some cases, the existing raster dataset is not replaced. Which action is taken is dependent on which raster type is being used to add the data.
Raster Dataset and NITF raster types
When data is added using the Raster Dataset or the NITF raster type, the raster dataset being added always overwrites the existing raster dataset.
CADRG/ECRG, CIB, and DTED raster types
When data is added using the CADRG/ECRG, CIB, or DTED raster types, ArcGIS first determines—based on the metadata extracted from the raster header—which is newer, the one being added or the existing raster dataset. If the one being added is newer, then the one being added overwrites the existing raster dataset; if the one being added is older, then the existing raster dataset is not overwritten.
How ArcGIS determines which is newer is based on the raster type. For CADRG/ECRG and CIB data, the NITF file date/time value is used for the comparison. For DTED data, the compilation, maintenance, and match/merge dates are used; the DTED dataset with the newest of these three dates is considered to be the newest.