IEEE Geoscience and Remote Sensing Magazine - September 2016 - 24

EasiEr accEss to Eo Data
EO data is becoming open and freely available due to the
initiatives of space agencies such as NASA and the European Space Agency (ESA). For example, data from the Landsat
program have been made freely available for a number of
years, and the same holds for ESA's Sentinel satellites.
The five Vs of big data are volume, velocity, variety, veracity, and value. EO data is a paradigmatic case of big data,
and they are available in big volume and a high velocity and
variety. For example, the Sentinel satellites are expected
to produce 5,000 TB yearly, with several terabytes of new
data arriving each day. EO data become useful only when
analyzed together with other sources of data (e.g., geospatial data or in-situ data) and turned into information and
knowledge. Finally, EO data sources are of varying quality
(i.e., veracity), and the same holds for the other data sources
with which they are correlated.
Linked data is a new data paradigm that studies how one
can make Resource Description Framework (RDF) data [i.e.,
data that follow the RDF (http://www.w3.org/TR/rdf-primer)]
available on the web and interconnect it with other data with
the aim of increasing its value. In the last few years, linked
geospatial data has received attention as researchers and practitioners have started tapping the wealth of geospatial information available on the web [1]. As a result, the linked open
data (LOD) cloud (LODC) has been rapidly populated with
geospatial data, some of it describing EO products (e.g., CORINE Land Cover and Urban Atlas published by the TELEIOS
project). The abundance of this data can prove useful to the
new missions (e.g., Sentinels) as a means to increase the usability of the millions of images and EO products that are expected to be produced by these missions.
However, big open EO data that are currently made available by space agencies such as ESA and NASA are not easily accessible, as they are stored in different data silos and,
in most cases, users have to access and combine data from
these silos to get what they need. A solution to this problem
would be to use semantic web technologies to publish the
data contained in silos in the RDF and provide semantic annotations and connections to them so they can be easily accessible by the users. The value of the original data would be
increased, encouraging the development of data-processing
applications with great environmental and processing value.
The European TELEIOS project (http://www.earth
observatory.eu/) is the first research effort internationally
that has applied linked data techniques to the EO domain.
TELEIOS was a European research project led by the National and Kapodistrian University of Athens that included
partners Centrum Wiskunde & Informatica (CWI), the
German Aerospace Center (DLR), Fraunhofer, and the Italian company Advanced Computer Systems. TELEIOS started in September 2010 and lasted for three years.
Some examples of applications developed in TELEIOS
include wildfire monitoring and burned scar mapping, semantic catalogs for EO archives, and rapid mapping. The
wildfire-monitoring application has been developed un24

der the lead of the National Observatory of Athens (NOA)
and is described in detail in [2]. It is available on the web
(http://papos.space.noa.gr/fend_static/) and has been used
operationally by government agencies in Greece since the
summer of 2012. Recently, the FIREHUB service on which
it is based won the best service award in the Copernicus
Masters competition (http://www.copernicus-masters.com/
index.php?kat=winners.html&anzeige=winner_bsc2014.
html) of 2014.
TELEIOS concentrated on developing data models, query
languages, scalable query evaluation techniques, and efficient
data-management systems that can be used to prototype the
applications of linked EO data. However, developing a methodology and related software tools that support the whole life
cycle of linked open EO data (e.g., publishing and interlinking) has not been tackled by TELEIOS. The main objective of
the European project LEO is to go beyond TELEIOS by designing and implementing software supporting the complete
life cycle of linked open EO data and its combination with
linked geospatial data and by developing a precision farming
application that heavily utilizes such data.
LEO brings together the two core academic partners of
TELEIOS (i.e., the National and Kapodistrian University
of Athens and CWI), two small/medium-sized enterprises
(SMEs) with lots of experience with EO data and their applications (i.e., Space Application Services and VISTA),
and one industrial partner with strong farm-management
information systems experience (i.e., PC-Agrar). LEO is a
two-year project that started 1 October 2013.
BiG oPEN Data iN tHE Eo DoMaiN
A plethora of EO data that are becoming available at no
charge (or only marginal cost) in Europe and the United
States recently reflects the strong push for more open
EO data.
THE LANDSAT CASE
The most important example of satellite imagery being
made available for free is probably the Landsat program
in the United States. After going through various pricing
schemes for selling Landsat data over the years, in 2008,
the U.S. government decided that data collected using the
Landsat satellites should be made available to users for free.
Although there is no market study that has articulated the
economic impact of this decision, the dramatic increase in
data downloads since opening up the data clearly shows its
importance. In 2001, when charging was still in place, approximately 25,000 Landsat scenes were purchased. From
2008 until recently, more than 9 million Landsat scene
downloads have been made. With Landsat 8 now in orbit, this open and free Landsat data policy is expected to
continue. A recent paper by the U.S. National Geospatial
Advisory Committee-Landsat Advisory Group has considered ten application areas of Landsat data and has estimated a savings of US$178-235 million dollars for federal
and state governments due to the free and open data policy
ieee Geoscience and remote sensinG maGazine

september 2016

http://papos.space.noa.gr/fend_static/ http://www.copernicus-masters.com/ http://www.w3.org/TR/rdf-primer http://www.earth http://www.observatory.eu/

Table of Contents for the Digital Edition of IEEE Geoscience and Remote Sensing Magazine - September 2016