Other expressions can make use of the value of (an array element of) a product variable as long as the product definition in which the expression is located has a product variable with that name. Each product variable has an expression that allows the product variable to be initialized. A product variable is a named scalar (a 64 bit signed integer) or a one-dimensional array thereof that is attached to the root of a product. Product variables can be seen as a caching mechanism for expression results (for expressions that are used to interpret the contents of an ascii/binary product file). For these situations the CODA product format definition system has been extended with a mechanism called 'product variables'. Product Variablesįor data with dynamic positions or lengths in raw ascii/binary data products, the calculation of a certain offset/size value can sometimes be quite time consuming, or it just can't be expressed easily in a single expression. ![]() no two data types or product types may have the same name) but when two types are located in different product classes then they are allowed to have the same name. This means that names within a product class should be unique (i.e. ![]() Product classes are also a way to prevent nameclashes between different product types. Within a product class, product types can share common format definitions for parts of the product (for instance: common ascii headers that are at the start of a product file). In order to make use of this commonality or standardisation in product formats, CODA categorizes product types into product classes. For these files there is usually some standardisation with regard to the product format that is used. For instance, a single satellite mission can produce many types of files. Product files are often part of a larger set of data files. This way, multiple versions of the same product type can be handled simultaneously (without the need to reconfigure CODA). Each version gets its own version number (normally starting with zero and increasing by one for each new version, but it can be any integer value). In order to deal with data from both the old and new version of the processor, CODA supports the concept of multiple versions of a product type. This can result in a change to the format of the output files (and if there is a product format specification document, then this document will also be updated). Sometimes a software application gets modified along the way. what data elements are stored and in which order, how numerical values are stored, etc.). Such a document explains in full detail how data is stored inside the product files (e.g. ![]() Two files can both be e.g HDF5 files but still have a different product type (because they contain different kind of information).įor some software applications the format of the generated data files are described in a product format specification document. Note that there is a difference between the main file formats that CODA supports (ascii, binary, xml, netcdf, hdf4, and hdf5) and the format associated with a product type. When a group of data files share the exact same file format, we say that they are of the same product type. When data files are generated by the same software application (using the same output options) these files will be identical with regard to the data format the way data is stored inside a file (its structure) will be the same, but the actual content of the files can (and of course often will) be different. software that corrects for instrument calibration parameters, retrieves physical quantities from raw measurement data, etc.). They are called this way because most data files are produced by data processing software (e.g. The data files that are supported by CODA are often referred to as products. CODA Product Format Definition Description Formatīelow we will explain the format that CODA uses to describe the Product Format Definitions for data products.
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