2.3 Definitions and Conventions

2.3.1 Definitions

2.3.1.1 Global and Regional Coverage

2.3.1.2 Auxiliary Data

2.3.1.3 Geolocation and Geocoding

Geolocation information is provided in the product header in the form of latitude and longitude information that allow the user to determine the area covered by the data from a simple inspection of the header. For image data, a geolocation grid may also be provided as an auxiliary data set in the product to allow for precise pixel geolocation.

Some image products may also be geocoded, which is the process of resampling the data to conform to a standard map projection with known coordinates.

2.3.1.4 Product Confidence Data

Product Confidence Data provides an evaluation of the overall quality of the product. As such, it is an evaluation of the product statistics as reported by various pieces of equipment and processors in the processing chain. Product confidence data is thus best represented by evaluating product statistics against predetermined thresholds to determine if the product meets the minimum quality requirements defined by the thresholds. If a product does not measure up to the predefined quality level, the error threshold is exceeded and a flag is set. (See also the section "Level 1B Essential Product Confidence Data." 2.6.2.3. )

• PCD in the MPH
  

  The MPH is a generic header (i.e., instrument unspecific), and so any product confidence data (PCD) contained within must be applicable to all instrument types.

  PCD applications include:

  • summary quality; high-level quality indicator for product
    
  • acquisition and de-multiplexing; this is related to the data commutation and downlink performance aspects which are independent of product type
    

  
  PCD in the SPH

  The PCD in the SPH may only contain information pertaining to the entire product length and relates to the execution of the product generation command (since a product will be generated by a single command). Examples include:

  • arithmetic error during product generation
    
  • auxiliary data files available/used during processing
    
  • mode usage statistics during orbital revolution
    
  • time relations used (predicted or precise)
    

  
  PCD in the DSR

  The PCD in the DSR, which was called Measurement Confidence Data (MCD) in ERS is referred to as PCD in the ENVISAT payload data segment. The DSR PCD provides details on individual source packet quality. It is related directly to the engineering aspects and details of the ground processing algorithms.

2.3.1.5 Calibration

Calibration data is classified as auxiliary data within the ADS

Internal calibration 2.11.3. data, contained within the instrument source packet, is used during the product generation process. The internal calibration information is generated by the instrument itself during the nominal measurement mode, or as part of a dedicated calibration mode.

External calibration 2.11.4. data, generated by on-ground or orbit calibration activities, is also used during the product generation process. The external calibration data is measured on ground, before launch, or in orbit during the commissioning phase or during periodic calibration activities.

2.3.1.6 Processed Product Sizes and Coverage

The Maximum Size of any product will be the smallest of:

• Data from a full orbit (100 minutes + potentially 10%, depending on OBR tape dump and specific acquisition downlink timing),
• Or, data from maximum continuous processed instrument/mode on-time (e.g., ASAR stripline [IM, AP, and WS modes] = 10 minutes),
• Or, the amount of data to fill a 2 Gbyte file. (In order to use standard UNIX file system capabilities, this limitation may be adjusted or removed as extended file sizes are fully supported.) If the amount of data is greater than 2 GBytes, the product is contained in multiple files, each no larger than 2 GB and each having its own MPH and SPH.

• ASAR IM/AP 100 km * 56 km (it may be larger (up to 100 km) for different swath choices)
• ASAR WS or GM 400 km * 400 km