It is widely accepted that the use of test sites for calibration and validation of Earth Observation sensors is good (if not essential) practise.
Such sites provide an ideal way of cross-comparing performance (biases) of different sensors.
Such sites help to provide a means of establishing a long-time base for climate change studies and linkage between different sensors for time base studies.
Appropriate targets are typically chosen on a mission by mission basis in order to suit the specific operational parameters of the satellite instrument with often different targets (sites) used for calibration and validation.
Sites need to have a range of characteristics, uniformity, stability, size, geographical position etc (details part of separate topic).
Sites ideally are characterised by some other independent means – visit by field team, viewed by another more accurate sensor from space or air, although only key parameters may need to be characterised dependent on application for example, temporal stability, for monitoring stability of a satellite sensor.
Some sites/targets have become “de-facto” standards by virtue of their wide useage by many sensors.
The cost of characterising and maintaining (information, instrumentation, quality) of sites is increasing and is often only supported by agencies to support specific missions.
The geographic location of ideal sites means that the cost burden is not uniform to all agencies.
Given the criticality of reference test sites for both Cal and Val and in the context of GEO, the importance of establishing a transparent means to identify biases and performance of different sensor and the resultant quality of their data products. it is proposed that the community identify a small sub-set of reference test sites (number to be determined), ensure they are well characterised and subsequently allocate to them some form of special designation e.g. “CEOS certified” so as to encourage their wide spread useage by the community.
This will:
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Discussion
Given the criticality of reference test sites for both Cal and Val and in the context of GEO, the importance of establishing a transparent means to identify biases and performance of different sensor and the resultant quality of their data products. it is proposed that the community identify a small sub-set of reference test sites (number to be determined), ensure they are well characterised and subsequently allocate to them some form of special designation e.g. “CEOS certified” so as to encourage their wide spread useage by the community.
This will:
- allow the community to focus efforts and resource on a few key sites
- improve understanding of performance of all sensors
- Lead to improvement in accuracy