On 9
September 2019, the consortium of the FFG-ASAP project Sen2Cube.at held a user requirements meeting at ZAMG premises in Vienna and presented the first prototype
of an operational Sentinel-2 semantic Earth observation (EO) data cube Austria.
During the meeting,
the academic partner (University of Salzburg, Department of Geoinformatics - Z_GIS) and the university spin-off Spatial Services GmbH presented
the newly developed prototype to the project partners AMA (Agrarmarkt Austria) and ZAMG (Zentralanstalt für Meteorologie und Geodynamik). In
the afternoon session, the meeting was open to a wider audience and other
interested users.
The presented prototype is the worldwide first
semantic EO data cube for Copernicus Sentinel-2 mission data. It provides new and innovative features, including semantic content-based
image retrieval and image analysis of all captured Sentinel-2 data through space
and time in user-selected areas of interest (AOI) and user selected time
intervals.
A semantic EO
data cube was defined as a spatio-temporal data cube containing EO data, where
for each observation at least one nominal (i.e., categorical) interpretation is
available and can be queried in the same instance (see Augustin
et al, 2019).
This approach
allows human users to query and
analyse EO data on a higher semantic level (i.e. based on at least basic land
cover units and encoded ontologies) directly in the data cube. A unique Web-interface
allows interactive human-like queries based on spatio-temporal and semantic
relationships. The requirements of different target user groups are met by explicitly
specifying spatio-temporal models as semantic queries and storing & sharing
them in a knowledge base. The semantic queries are translated by an inference
engine into data cube queries and executed on-the-fly on the server-side against
the data cube, where the new information is inferred. Results depend on the semantic
query and include (1) analysis maps for online use or as download option for
integration in any GIS, (2) time series curves for aggregated results per AOI,
or (3) the selection Sentinel-2 data sets that match user-defined criteria for
downloading and further analysis
The semantic
EO data cube is generic, meaning it is useful for multiple thematic domains. Its
potential is demonstrated in the Sen2Cube.at project by developing different
services in a proof-of-concept environment for Austria.
Already implemented services include:
*Semantic content-based image retrieval, e.g. for cloud-free image retrieval based on user-defined AOIs instead of image wide statistics, which is not possible in any other Sentinel-2 image database worldwide.
*Spatio-temporal analysis through time analysing the semantic categories through time for any user-defined AOI and/or time span.
A
In the second
half of the project more services are developed. They will allow the generation
of cloud-free mosaics for user-specified time intervals and the development of
a mobile App for location-based queries through time. The prototype will be scaled up to the entire country of Austria, covering all
available Sentinel-2 images since the launch of Sentinel-2A in 2015. The semantic EO data
cube is implemented at EODC infrastructure; since July 2019, Z_GIS is also an associated partner of
the EODC.
The Web-interface prototype serves as graphical inference engine and allows interactive human-like queries based on spatio-temporal and semantic relationships. Requirements of different user groups can be met by explicitly specifying and sharing spatio-temporal models in a knowledge base (here: analysis of water occurrence through time)
Semantic content-based image retrieval in user
defined areas and user defined time intervals covering all available Sentinel-2
data within Austria, here: cloud-free image retrieval for a user selected AOI
for July 2018 (image IDs of cloud free images are returned and a statistic of
the cloud cover of the AOI for all analysed images).
Contact: Dirk Tiede, Martin Sudmanns
