The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
database. The inventory is created or updated for a quick 
overview of the database's content. 
Data Tiles have to be resampled to lower resolutions to provide 
a fast access to the needed accuracy later. In case of the Image 
Chips the chip list is updated, no resampling of the data is done. 
Tracks are partitioned to fit in the tiles where they are stored, 
and the track list is updated. 
For each data type the components are zipped to save memory 
space. 
6.2 Export 
6.2.1 Data Tiles 
The export routine for data tiles comprises the following steps: 
• get DEM tiles from the addressed project(s), 
• mosaick DEM tiles to one file per project, 
• cut out a specified part for each project, 
• fuse information from different layers to one file, 
• apply coordinate transformation to target projection/ 
coordinate system. 
6.2.2 Image Chips 
The export routine for image chips accomplishes the following 
function: “for a given region of the earth's surface (specified by 
the comer coordinates) provide me with all image chips 
intersecting this region”. 
6.2.3 Tracks 
The export routine for tracks accomplishes the following two 
functions: 
• “for a given region of the earth's surface (specified by 
the comer coordinates) provide me with all points 
stored in tracks within this region” , or 
• “for a given track provide me with all points situated 
within this region”. 
Both functions are assured by the help of the track list stored in 
each tile. 
6.3 Update 
Update routines for all data types have the following steps in 
common: creation and deleting of lock files providing exclusive 
file access, and the update of log files and inventory. 
Data tiles can be updated at any level. The coarser resolutions 
in this case have to be updated as well. The update of an image 
chip has to be interpreted as a replacement of an existing chip 
by a new chip. The identification of the chip to be updated is 
done by its unique identifier. In this case the tile specified with 
its unique identifier is replaced. 
For updating tracks insertion and deletion of points into or from 
a track have to be foreseen. 
6.4 Inventory 
For each file type an inventory function is foreseen that is 
capable of providing an overview of the data stored within 
(parts of) the project. 
6.5 Maintenance 
The maintenance module for each data type should be capable 
of providing the following functionality: undoing the last 
creation/update step, removing files from archives and 
inventory lists, erasing complete directory trees, backing up 
(parts of) the directory tree, copying (parts of) the directory tree. 
All of the above functions can only be simulated. Only listings 
are prepared in this case. 
7. FILE ACCESS ROUTINES 
The functionalities provided for the handling of raster and 
vector data are displayed in table 3. This comprises seven 
classes of basic functions: 
• file format conversion routines for the support of 
different in- and output formats, 
• routines to allow the manipulation of the file content, 
• modules to display the information content of the data, 
• visualization utilities, e.g. for the generation of color 
shaded presentations, 
• algorithms to fuse overlaying tiles in different 
resolution and qualities, 
• utilities to allow the mosaicking of data, 
• methods to resample the data to different resolutions 
or coordinate systems. 
Raster 
Data 
Raster and 
Vector 
Data 
Vector 
Data 
Data Conversion 
X 
X 
Data Manipulation 
X 
X 
Data Information 
X 
X 
Data Visualisation 
X 
X 
Information Fusion 
X 
X 
X 
Mosaicking 
X 
X 
Resampling 
X 
X 
X 
Table 3. File Access Functions 
7.1 Data Conversion 
Conversion routines between common generic image 
processing formats with a geographic representation have to be 
foreseen. At the moment the exchange between files in SRF, 
GeoTiff, and DTED format is supported. 
Conversion routines from sensor specific formats (e.g. IceSat 
data) to shapefiles has to be implemented for Tracks. 
7.2 Data Manipulation 
Modules are implemented to 
• allow various file manipulation actions for SRFs, 
• add or subtract the geoid undulation to or from a given 
SRF, 
• manipulate SRF header and/or footer content, 
• create simple synthetic patterns in SRFs, 
• rotate a given SRF clockwise by a given angle, 
• mirror given SRF at the horizontal and/or vertical axes, 
• allow the separation of shapefiles according to spatial 
or attributive criteria. 
7.3 Data Information 
At the moment the following functionalities are implemented to 
show the information contained in the elevation data: 
• creation of difference images of given SRFs, 
• calculation and display of statistical values, 
1257