The Committee on Earth Observation Satellites (CEOS), defines validation as the process of assessing, by independent means, the quality of the data products derived from the system outputs.
The MODIS Land Validation Strategy
MODIS Land (MODLAND) product quality is ensured by Calibration, Quality Assurance (QA) and Validation. The MODIS
land validation effort will contribute to and leverage off of international validation activities, helping to establish
standards and protocols through close coordination with the CEOS Land Product
Validation (LPV) subgroup, under its Working Group on Calibration and Validation (
WGCV).
MODLAND uses several validation techniques to develop uncertainty information
for its products. These include comparisons with in situ data collected over a distributed set of validation test sites,
comparisons with data and products from other sensors (e.g., ASTER, AVHRR, MISR, TM/ETM+), intercomparison of trends
derived from independently-obtained reference data, and analysis of process model results.
MODLAND's primary validation technique includes the collection of field and aircraft data, and comparison
with these and with products from other satellites. The infrastructure for these efforts has resulted in the
establishment of a semi-permanent array of EOS Land Validation 
, most of which include a flux tower for extended temporal
measurement of terrestrial biophysical dynamics over a range of landcover types. Field data are archived in
cooperation with the Oak Ridge DAAC's Mercury system. Results of all validation activities are conveyed to the
end-user through both published literature and the MODLAND product 
pages.
Validation Hierarchy
-
Stage 1 Validation: Product accuracy has been estimated using a small number of independent
measurements obtained from selected locations and time periods and ground-truth/field program efforts.
- Stage 2 Validation: Product accuracy is
estimated over a significant set of locations and time periods by comparison with reference in situ or other suitable
reference data.
Spatial and temporal consistency of the product and with similar products has been evaluated over
globally representative locations and time periods.
Results are published in the peer-reviewed literature.
- Stage 3 Validation: Uncertainties in the
product and its associated structure are well quantified from comparison with reference in situ or other suitable
reference data. Uncertainties are characterized in a statistically robust way over multiple locations and time periods
representing global conditions.
Spatial and temporal consistency of the product and with similar products has been
evaluated over globally representative locations and periods.
Results are published in the peer-reviewed literature.
- Stage 4 Validation: Validation results for
stage 3 are systematically updated when new product versions are
released and as the time-series expands.
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