MODIS Validation Strategy
Overall Approach
MODLAND product quality is ensured by Calibration, Quality Assurance (QA) and Validation.
MODLAND uses several validation techniques to develop uncertainty information on 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 airborne and spaceborne sensors (e.g., SeaWiFS, AVHRR, MISR, TM/ETM+, ASTER), inter-comparison of trends derived from independently obtained reference data and MODLAND products, and analysis of process model results which are driven or constrained by MODLAND products. Additional land validation activities can be found on the CEOS WGCV Land Product Validation subgroup web site (lpvs.gsfc.nasa.gov).
MODLAND's primary validation technique includes the collection of and comparison with field and aircraft data, and comparison with data and products from other satellites. The infrastructure for these efforts has resulted in the establishment of a semi-permanent set of EOS Land Validation Core Sites, 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. Results of all validation activities are conveyed to the end-user through both published literature and Product Specific Validation information Validation menu.
CEOS LPV Validation Hierarchy
- Stage 0 Validation: No validation. Product accuracy has not been assessed. Product considered beta.
- Stage 1 Validation: Product accuracy is assessed from a small (typically < 30) set of locations and time periods by comparison with
in-situ or other suitable reference data. - 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 consistency 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 rigorous 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.
Measures of Success
Successful validation is accomplished if timely and accurate product uncertainty information becomes routinely available to the product users. Product-specific Validation information is posted on the MODLAND web site under the Validation navigation tab above. As improvements and modifications to the MODIS algorithms develop and new collections are generated, this validation information is updated, with the goal of providing accuracy statements for the most current version of each MODLAND product.
