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Sharing and cooperation in geo-information technology
Aziz, T. Lukman

To manage and retrieve satellite imagery data, image data is
considered as a Binary Large Object (BLOB) multimedia type
data. Multimedia type data has it own data management and
query system. A Standard Database Management Sytem
(DBMS) can perform exact matching query (using SQL) from a
database tile. A Spatial Database can perform suitability
analysis using spatial algebra. An image database has a special
query type data retrieval called similarity (Guivada, 1995).
Two major issues about variation in data management will be
discussed. Metadata is a brief description of image content,
format and contents that depends on each user. Image data
format is a binary data format that allows the storing of multiple
layer information.
Content Based Information is a way of information handling on
image file. QB1C (Query By Image Content) uses color, texture
and shape to retrieve image similarity. One content based
approach is Entity Relationship Diagram (ER-D) of Picture
(C.Yu, 1994). Figure 1 show an example of ER-D of a picture.
Figure 1
Example ER-Diagram of Image / Picture Data (C.Yu, 1994)
Retrieving Image data using Spatial and Temporal Data has
been introduced by Mohammad Nabil (1997), replacing text
based metadata with content based information. The model that
introduced by Nabil is 2 Dimension Projection Interval
Relationship (2D-PIR), which uses a directed graph data
structure to represent network of objects and their spatial
2D-P1R model use a projection of an image into a set of
polygon vector that reflects shape and position of each
important part (content) of image. The process to create a shape
polygon from raster image can be a manual sketch or automatic
shape edge detection using Artificial Intelegence technology.
From this vector, 2D-PIR model generates a spatial relationship
that record relationship among vectors (topology) in one image,
started from upper-left side of image. The format of this record
is a linked list that records list of objects which has spatial
location on the right side of referenced object. Figure 2 show a
simple sketch of 3 object from an image data (A, B and C) and
its 2D-PIR linked list scheme. Each record in linked list contain
polygon code and its spatial relationship code.
3.1 Metadata and file format
Current image data handling is organised by metadata or a
header file in ASCII text format. Metadata files contain
important information about what is stored in an image file, and
how the data is stored (file format). Some example of important
information that stored in metadata files are : Location
Information, Coordinate System and boudaries, Projection
Information, Sensor type, Acquisition date and description of
image content.
Metadata (in the above format) , helps user to make a quick
assesment of the image data before actually retrieving the image
data file. Its content is depend on user who create the metadata.
The interpretation of metadata is also a manual interpretation
process, and is followed by manual image data retrieval.
3.2 Data independence
Current image data handling varies depending on remote
sensing software. Although Remote Sensing software can read
many types of Image data format (BIP, BIL, BSQ, or original
format of Satellite Imagery or), each software use their own
proprietary format to store and manipulate image file. In ER-
Mapper, simple Image data management can be implemented
using Algorithm file. We can create an algorithm that handle
multiple image surface, example of ER-Mapper algorithm is
shown in figure 3.1.
Figure 3.1 : Temporal data handling using ER-Mapper
Algorithm file.
The objective of this approach is how to support Remote
Sensing Software with a data management tool to record image
file location and image file information, including temporal
informations to perform historical data query. File location is a
file search path of the image file. In local stand-alone storage,
this search path may contain a volume code in a directory path;
in a network, the file search path may contain the machine name
or an IP number or generally the URL. Using an URL to locate