Calibration and Validation of State Wide Land Cover Mapping

The Victorian Land Use Information System (VLUIS) produces an annual land information product for the state of Victoria. It comprises three important characteristics of land information: tenure (ownership), use (property type), and cover (physical surface). The land cover component is created using a remote sensing approach. Using MODIS EVI 16-day image composites (MOD13Q1) collected over 12 months, phenology metrics such as start, end and length of the growing season are derived using the TIMESAT program. These metrics are used as input into the C5.0 program to derive a rule set to produce an annual state wide land cover classification product. A significant portion of the resources and time required to generate a land cover product is spent collecting ground data to develop the rule sets for calibration and to validate the created product. Ground data collection is undertaken once a year from October through to December. Data is collected using a stratified random sampling approach. Initially the state is stratified by Primary Production Landscapes (PPLs) which divide the state into six regions based on terrain, geomorphology, soil types, climatic conditions, and land use and management information. Using the 1:25,000 scale map grid of the state, a random selection of map grids from each PPL is taken. Within these grids, parcels that were accessible within 20 m of formed roads are selected and, from within this selection, only parcels greater than 25 ha, after imposing a 150 m internal buffer, are chosen to allow for at least one MODIS pixel (250 m x 250 m) in each parcel. This basic sampling framework has been used to collect ground data since 2009. To produce a random sample at minimal cost some map grids are resampled each year, while others are randomly added or taken out of the target sample. Some rare land cover classes, such as woody and non-woody horticulture, are not adequately sampled using this approach. A secondary sampling phase is used to target underrepresented land cover classes to ensure an adequate sample size for calibration and validation is achieved and from these supplementary data sets, a random selection is taken for validation. This paper outlines the approach taken for collecting calibration and validation ground data used to produce the VLUIS state wide land cover classification product.