input: [Status] Is being processed [Applies to...] Data, layers [Description] 
output: This message includes an indicator of the processing phase, such as [Step 1 of 3], as described below. For a data source: Maps Engine is converting a data source upon upload. Maps Engine creates a data source entry in its catalog upon start of the upload, first giving it a status of Uploading and then a status of Is being processed. The steps for imagery data sources are: metadata validation: checking the data source description sanitization: securely reading the pixel data encoding: converting the data to a neutral format for further use generating thumbnail: creating the image used with the data source The steps for vector data sources are: data fetch: obtaining the data from the data source data conversion: making type conversions as needed data ingestion: writing the data into Google's internal storage For a layer: Layer processing is in progress. The two steps are: ingestion: writing the layer into Google's storage as a new entity blend: performing graphical fixes such as seaming, feathering, and so on.