ceos - 13 may 2003 alain giros - image processing and quality division 1 information mining in...
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CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division1
INFORMATION MINING
IN CATALOGS
OF REMOTELY
SENSED IMAGES
INFORMATION MINING
IN CATALOGS
OF REMOTELY
SENSED IMAGES
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division2
The need for catalogs of imagesThe need for catalogs of images
Images acquired by remote sensing satellites are : Numerous : after 16 years of operation, SPOT satellites have acquired
more than 10 millions scenes all over the world
Big : the size of a SPOT image ranges from 27 to 2150 Mbytes
Diverse : Numerous sensors (optical and SAR) are available with different characteristics
Users (distributors, final users, …) need tools for browsing image archives in order to select those which fit their needs.
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division3
Current catalogs of imagesCurrent catalogs of images
Current tools are mainly based on the use of descriptive data, which are used as indexing data :
Geographic location
Sensor characteristics
Viewing date
Constraints expressing relationships with other data (stereoscopy, …)
2D index of some information which impacts the image use (snow, clouds, acquisition quality, ...)
...
The image content is displayed only as quick-look images together with the selected data ; its interpretation is left to the user.
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division4
Existing Catalogs PrincipleExisting Catalogs Principle
“Semantics”
Localization
Date & Time
SensorImage
Archive
Index
BrowseEngine
Analysis and VisualizationTool
Result
Catalog
Request
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division5
Some Catalogs ExamplesSome Catalogs Examples
SIRIUS Catalog for SPOT images Local : demo Internet : http://sirius.spotimage.fr/francais/Welcome.htm
Catalog of VEGETATION images Internet : http://cat.vgt.vito.be/login_french.html
...
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division6
Present catalogs inefficienciesPresent catalogs inefficiencies Image content is not used
Except through rough indexes on clouds, snow or technical quality
The interpretation of the results of queries is left to the user No assistance is provided to the user
The user’s interests are rarely taken into account A given request gives the same results whoever the user is
Catalogs are passive They could be more dynamic in order to propose images by themselves
Multi-sensors searches are difficult to achieve Catalog interoperability does not exist at image content level
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division7
Consequence of the inefficienciesConsequence of the inefficiencies
Remotely sensed data are not accessed enough
Acquired
Usable
Consulted
Exploited
Acquired
Usable
Consulted
Exploited
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division8
New generation of catalogsNew generation of catalogs
Catalogs with a more dynamic behaviour : Exploit the content of the images for their selection
Take the user’s interests into account
Assist the user in the browsing process
Attract the user through personalized proposals (subscription)
...
The aim being to make the access to the relevant images easier, in order to increase their spreading and their use in applications.
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division9
Use of quick-looks contentUse of quick-looks content
The content of quick-look images can help answer only a limited number of questions :
What are the changes which happened at the quick-look scale (macroscopic change detection) ?
What are the resemblances between images based on macroscopic criteria (i.e. radiometry) ?
Are there contextual phenomena which could prevent the exploitation of the full resolution image (clouds, snow, …) ?
… ?
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division10
Resolution/Information trade-offResolution/Information trade-off
By definition a quick-look image does not contain all the information of the full resolution image.
When a quick-look image is generated by a subsampling process (1:5 to 1:10), the information changes :
In a 1m resolution image, urban features are recognized
In a 10m resolution image, they are hardly seen
In a commercial system, a free image must not contain this information.
In order to exploit a catalog of images by their content : Full resolution images must be used in order to access valuable
information
They must not be shown (free of charge)
CEOS - 13 may 2003 Alain Giros - Image Processing and Quality Division11
The challenge of the full resolution imagesThe challenge of the full resolution images
There is a huge volume of data to manage : SPOT 1-4 :
10 Millions scenes
30 MegaBytes per scene
» 300 TeraBytes It is thus impossible :
To have all the full resolution images online
To exploit them directly for each request
As a consequence : A digest of the image limited to the « just needed information » must be used
during the processing of the queries.
This information must be extracted on the fly just after the acquisition.
SPOT5 : 2 Millions scenes
150 MegaBytes per scene
» 300 TeraBytes