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4 Data Systems
Pages 39-43

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From page 39...
... .1 Freely available data from USGS -- not only Landsat data, but also airborne imagery and data on topography, hydrology, land cover, and so on -- are widely downloaded and applied to scientific research and resource management. A number of products based on Landsat are available, along with a rich set of related map and imageryderived products.
From page 40...
... There is potential for a far greater array of derived products than are currently available. If appropriately defined and funded, sustained land imaging capabilities would enable a myriad of products and services, including many essential climate variables and climate data records.
From page 41...
... The Landsat Surface Reflectance product is an excellent example; it is produced routinely for selected time periods but is also available on demand for specific Landsat scenes. Algorithm Development and Calibration/Validation As the focus in Landsat and other space or airborne data acquisition systems evolves from providing imagery to providing higher-level data products derived from those images, a set of consequent activities becomes necessary.
From page 42...
... The Sustained and Enhanced Land Imaging Program should develop a systematic process for identify­ ing and prioritizing a wider suite of products, including essential climate variables, that can be derived 11  The international Committee on Earth Observing Satellites has advocated a universal validation data set for all global land cover products to increase the interoperability of data from many countries' satellites. It also emphasizes validation and accuracy assessments as a major part of a mapping program.
From page 43...
... DATA SYSTEMS 43 from moderate-resolution land imagery, and for documenting and validating algorithms, including their modifications or replacements. In doing so, the program should • Define criteria that government-provided authoritative data sets should meet, among them such attributes as calibration, accuracy assessment, and validation, and including ground truth; • Define criteria for which products should be provided by the government and which by the private sector; • Implement procedures for development, cost estimation, peer review, and the publication of algorithms that produce derived products; and • Implement plans, procedures, and budgets for ongoing validation.

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