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).