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Acceptation of Earth observation information by GIS users
National Aerospace Laboratory, Space DepartmentUNIGIS intake march 2002
Edwin Wisse
16 June 2006
Acceptance of Earth observation 2
Introduction: Earth obseravtion
History 1972, Landsat-1 first dedicated
Earth observation satellite 1986, SPOT-1: 10 metre
panchromatic, 20 metre multispectral
1991, ERS-1: imaging radar 1999, Ikonos: high resolution
optical satellite (1 metre pan, 4 metre multspectral)
Applications Scientific Agricultural and environmental With hogh resolution satellites:
planning and surveying
Acceptance of Earth observation 3
Introduction: acceptance
Earth Observation has so far failed to evolve into a mature and self-sustainable operational or commercial activity. Hence, it has not allowed the development of a service industry of any economic significance. (Achache, Director of EO ESA, 2003)
In numbers: Public sector (mostly defense) forms 64% of the market. Private sector: mostly telecommunications (planning mobile phone
networks) plus oil and gas Annual growth over 1998-2000: 1.4% (that’s decline)
Problems and solutions Findability. O2 (ESA): build infrastructuur Availability. Rapideye: use Constellations Usability. Error and resolution aspects are not sufficiently
understood and applied
But what are exactly the weaknesses in Earth observation according to users?
Acceptance of Earth observation 4
Introduction: ideal Earth observation
Satellite watches over Duckburgh constantly (temporal resolution)
Fine tune button for easy zooming (spatial resolution) It’s free! Images can be received from the air (availability)What you see is what you get (error aspects)
Acceptance of Earth observation 5
Study problem
The question we want answered is:
What factors are decisive in user acceptance of Earth observation information by GIS users?
This can be formulated as two consecutive questions:What are the different factors?How strong do they affect acceptance?
Why GIS users?
Talks with other UNIGIS students showed me that most found EO very interesting and promissing, but very few were aactually using it.
But how can we test acceptance?
Acceptance of Earth observation 6
Technology acceptance model
Based on the theory of reasoned action, people base their decisions on a chain of factors. Intention to use affects actual usage, and the attitude of a person affects intention.
This was extended to the Technology Acceptance Model. In TAM usefulness and ease of use are introduced. These affect the attitude.
TAM contains methodology for measuring the strenght of the constructs.
TAM has been used to test acceptance of software tools, phones, services etc.
Acceptance of Earth observation 8
Technology acceptance model
TAM uses a standard scale to measure the relations between the contructs:
Using TestTool in my job would enable me to accomplish tasks more quickly
Using TestTool would improve my job performance ... It would be easy for me to become skilful at using TestTool I would find TestTool easy to use
Standard TAM is based on the perceived usefulness and ease of use constructs.
In later studies factors affecting the constructs have been introduced: enjoyment, functionality, interactivity etc.
Acceptance of Earth observation 9
Earth observation: sensors and image types
Optical easy to interpret hindered by cloud cover,
especially over the Netherlands
high resolution means small swath
with high resolutions the look angle of the sensor and shadows become significant
Radar: looks through cloud cover coarse resolution sensitive to different
materials than optical
Acceptance of Earth observation 10
Earth observation: (classified) maps
Thematic maps from EO images: classified maps
Use spectral models to derive soil type, vegetation from pixel values
More channels (colours) give better results
Coarser resolution gives better results
Classified maps either errors (wrongly classified pixels) or they are incomplete
Acceptance of Earth observation 11
Earth observation: parameters
What are the factors affecting acceptance? (see study problem)
Spatial resolution Temporal resolutionErrors and uncertaintiesRepresentation: file format, how is
the data delivered?Availability: how to find data?
How do these parameters relate to the usefulness en and ease of use constructs?
Acceptance of Earth observation 13
Modified TAM: the scale
The modified scale was designed to measure the affect of the parameters on the constructs:
The spatial resolution of optical images is sufficient for my needs Optical images are acquired often enough for my needs Thematical maps (classified images) with a classification error are
usable for me An error-free, but incomplete, thematical map or classified image is
useful for me ... Importing Earth observation imagery and information into my GIS
environment is easy for me I know how to find and order the Earth observation images I need
An additional 4 questions from the standard scale were introduced to measure the affect of intention.
Acceptance of Earth observation 14
Questionnaire session
ArcGIS user day at NLR:Presentations about EOVisit to ground stationEn de questionnaire sessie
Session:Controlled environment2 sessions of 14 peopleText of the presentation was read
from paperThe subjects used a voting remote
control Interactive interface to select,
compare and zoom into sample images
Acceptance of Earth observation 15
Results: the subjects group
The subjects group:
Predominantly GIS users with little EO experience (good!)
More than half were from government: municipalities and provinces
Subjects who indicated that they had daily experience with EO were excluded from the following analysis. This left 25 subjects
Acceptance of Earth observation 16
Results: spatial resolution
The subjects rate: traditional EO imagery (10 metre resolution) neutral high resolution imagery more usefull radar imagery negative
Acceptance of Earth observation 17
Results: temporal resolution
The subjects rate: Despite the differences between optical and radar there is little
difference in the responses All subjects are neutral to positive to the temporal resolution issues
Acceptance of Earth observation 18
Results: error aspects
Error aspects related results: Incomplete maps as more
useful than maps with errors A georefencing error is not
acceptable Visulatisation of errors in GIS
leads to high perceived usefulness
Acceptance of Earth observation 19
Results: usefulness and ease of use constructs
4 questions refered directly to the usefulness and ease of use constructs
Subjects are neutral to positive about usefulness
They see no problems with ease of use
Acceptance of Earth observation 20
Results
Reliability: The wide spread of he questions
has resulted in a low, but acceptable reliability.
Correlations: Strong correlations between
spatial, temporal and error paramaters and perceived usefulness.
Also a strong correlation between representation and availability and the perceived ease of use.
Smaller (but significant) correlation between perceived usefulness and intention to use.
The perceived ease of use construct is weak in the modified TAM (but that was to be expected)
Construct Items Reliability
perceived usefulness 12 0.3486
perceived ease of use 5 0.4916
Davis’ PU 2 0.7985
Davis’ PEU 2 0.4270
intention to use 2 0.7255
Perceived usefulness
Perceived ease of use
Spatial resolution 0.639 -0.207
Temporal resolution 0.526 0.078
Error aspects 0.501 0.303
Representation 0.323 0.587
Accessibility -0.116 0.580
Acceptance of Earth observation 21
Conclusions
Earth observation and GIS: Subject group needs high resolution data (1 metre is still not
sufficient), acquisition is already often enough for this group. They are aware of the different errors and would like to see
error representation in their GIS application. Representation and availability are not seen as problems.
Modified TAM: Good first result Ease of use is weakly defined Future study: use less parameters (and more subjects)
Unigis: Unigis provides an excellent opportunity to step out of your
own field of expertise and learn something different