HDR-records are the only type of information for which 
direct access has been provided, Besides of this PODIUM 
uses the following three access methods: 
- indirect access, 
- BD -trees /1.,3/, ; 
- ‘GCirculariy and doubly linked lists (CADLL) /2/. A 
To support these procedures a HDR-record contains all 
the 
- links to the appropriate records upon indirect access, 
- links to root nodes for B*-trees, 
- printers for CADLL's. 
For each type of information the access method being 
most likely has been selected. 
Without respect to their type of information PODIUM 
stores records consecutively and contiguously with the 
following two exceptions: 
- hard sectoralignment has been optionally provided for 
the records of some types of information, 
- the erasure of information yields gaps (there is an 
integer defining the maximum number of gaps to be 
controlled by PODIUM by means of a header contained 
table). 
5. Image-oriented types of information 
  
Probably the most important type of information is the 
image data itself. Fig. 2. illustrates the common 
manner of referring to the elements of a multi-spectral 
digital image, whereeach tupel consisting of a valid row/ 
line number and a valid column number determines a so- 
called pixel. 
Upon analysing remotely sensed image data one would often 
like to refer to pixels by means fo UTM coordinates. 
PODIUM supports this, too. 
Almost everybody talkingabout pixels automatically thinks 
of integers between zero and some power of two. But 
spectral reflectance factors for example are reals and 
avoiding losses of precision implies the demand for real- 
number-oriented storage methods. These are also provided 
in PODIUM.