and customize the information content via their WWW
browser. ImageNet from CORE Software Technology Inc.
(CORE, 1995) supports data browsing and retrieval via WWW
and a special purpose client. Furthermore the WWW Ionia
AVHRR Net Browser (Mungo, 1994), the Arno project (Nativi,
1995) and the Landsat/Spot browser by the Canadian Center for
Remote Sensing and Earth Observation (CEONet, 1995) should
be mentioned.
In comparison, there is no proliferation of systems for planetary
data retrieval. Publicly accessible applications for planetary
data retrieval, provided by the member institutions of the PDS,
allow searching databases for named features, or for image
coverage by defining either a point or a region of interest. Two
collaborative projects have recently started at NASA's Jet
Propulsion Laboratory (JPL) and the US-Geological Survey
porting raster and vector representations, offering image proc-
essing facilities, sharing resources and dealing with distributed
archives. Image data are conventionally organized by type of
sensor, by satellite, by time of data acquisition and not by spa-
tial coverage. It is the image's position or its coverage that a
scientific user most likely uses in his queries. A distributed
heterogeneous system like the GDSS giving remote access to
image data has to support data exchange standards such as the
International Directory Network (IDN) or Z39.50, a flexible
scalable network structure, remote access to special hard- and
software resources and transparency in terms of hiding the
system's architecture from the user. The usage of available
standards should be obligatory but is usually ignored.
3. PRELIMINARY SYSTEM DESIGN
(USGS): Planetary Image Access (PIA, 1995) and Interactive
Planetary Atlas (IPA, 1995).
Current systems are greatly limited in their abilities such as user
defined image cropping, billing for services and data, using a
flexible network with high bandwidth, user management, sup-
3.1 Design Goals
The design goals are summarized in Table 1.
Goal
Raster Image Oriented Browsing Interface
Purpose
Planetary data suffer from a lack of named features. A zoomable raster image
oriented browser interface is needed.
There is a need to handle queries for points and regions of interest via a spatial
Search for Points and Regions of Interest
database. A reply with lossy compressed (>1:25) quicklooks of the available Fig
image data is useful. anc
Coverage Requests Image data may be the subject of queries regarding the coverage with stereo, by
a specific mission “cycle“ or a particular type of feature. Coverage results will be 3.2
visualized at the client site by overlaying colored areas (e.g. green areas showing The
stereo coverage) Jis
Searching for Meta Information Support of additional search criteria which can act as a filtering function on the ;
data is needed, like addressing a cycle number, date or/and time, type of sensor, The
data processing history, computation algorithm, processing parameters. will
Client-Server Architecture The underlying concept of the system is a distributed client-server architecture
(Vaughn, 1994) with an ATM backbone. The benefits of ATM include easy na
scalability, high-bandwidth, guaranteed quality of service, physical layer inde- pub
pendence and support of connection-oriented and connection-less services. ard
Intelligent Local Caching This feature keeps response times short and reduces network traffic.
Local server data prediction The Retrieval Client connected to the Local Server has to download and Loc
visualize special rectangular data structures denoted as "map tiles". They exist at is re
different levels of detail. To achieve high speed for interactivity the Local Server ager
loads predicted tiles around the current user position and also tiles of the adja-
cent superior and inferior level of detail. The
Batchjob Processing The user has a batchjob interface for processing standard procedures in the back- form
ground or during times of low use or cheap network connection (e.g. night). over
User group management Clients can be connected to one Local Server, resulting in the need for user bord
management which includes building user groups, definition of user rights and featı
defining priorities. marl
Network Security and Accounting For commercial use a system must provide accounting facilities. Hence identifi- avail
cation, authorization and charging is required. In such cases the system must
guarantee privacy of communication. The
Network management capabilities Extensive O&M (observation and maintenance) features must be available to avail
manage a system with global scope. These are addressed by performance obser- (Asy
vation and tuning, monitoring, security management, fault management CCr
(diagnostic tools, trouble ticket generation, ...) and configuration management. desig
Remote Data Processing Special image processing facilities should be available on the distributed system. trans
Therefore it would be useful to have a special remote processing interface for conn
typical image processing algorithms. While histogram manipulation, con- isoch
trast/brightness correction, filtering etc. are standard procedures, 3-D terrain the (
restitution by shape from shading methods is not. The system needs to support high
computing at a Central Server, delivery of the results to the user and accounting. ise
Mc
Table 1: Main design goals of the GDSS with a brief description of its purpose ATN
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996
