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Tables in Image Processing
The purpose of image processing systems is to extract information from image
data. Systems which are designed to treat large numbers of images must also be
able to analyse the data extracted from the images. The standard Database
Management Systems (DBMS) provide many of the facilities needed; however, some
of the desired interactive graphics, statistics, and mathematics are not
always available. Therefore, a dedicated table system has been made to serve
these purposes in MIDAS (Grosbøl and Ponz, 1985,
Mem.S.A.It., 56, 429).
The use of tables can be divided into three main categories: internal,
external, and user applications. One of the advantages of the MIDAS Table
System (MTS) is that tables for these different purposes have the same
structure and can be treated with the same set of routines. The three
categories are discussed separately, although there is some overlap in the
applications.
- Internal tables
- are mainly used by MIDAS to compute transformations
which later will be applied to images. Typical examples are dispersion
relations, characteristic curves and coordinate transformations.
- External tables:
- During a reduction procedure, data from external catalogs
or data base may be needed. This information can be made available by
transferring them to the MTS format. Examples are given: catalogs of
photometric data which can be used to establish transformations from
internal magnitudes to a standard photometric system, or astrometric
catalogs for computations of accurate reference frames for images.
- User tables
- are used for storage of values computed during the
reduction (e.g. stellar magnitudes, line intensities, or isophotal
diameters of galaxies). This provides an easy way to save such
heterogeneous data in a computer readable format. Further, the user can
investigate the properties of the data (e.g. distributions and
correlations of different values, and so on).
Next: Structure of Tables
Up: Table File System
Previous: Table File System
Petra Nass
1999-06-09