ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata
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The dataset maps areas of winter forage cropping and intensive winter grazing occurring in hill country areas during 2018. Hill country is defined as areas where paddocks have an average slope of greater than 7 degrees. Paddocks are classified into crop type and a measure is provided of the proportion of bare ground within the paddock after grazing.
This hill country winter forage mapping was undertaken to quantify the extent of the issue to support policy development under the Essential Freshwater package.
This winter forage mapping is based on a time series of Sentinel-2 satellite imagery captured between 1 September 2017 and 20 November 2018. Scenes within minimal cloud were selected, calibrated and masked for remaining cloud. Using this time series, paddock boundaries were identified from spectral variation. The average slope for each paddock was calculated based on the Manaaki Whenua - Landcare Research 15m digital elevation model (originally derived from LINZ 20m contours). The mapping extent was then constrained to agricultural areas based on LCDB4.1 cropland and grassland classes. The landslide class was also included here. The mapping extent was further restricted to paddocks with an average slope over 7 degrees. Paddocks within the mapping extent were classified into crop type based on imagery acquired in autumn/early winter. Winter forage cropping paddocks and paddocks showing evidence of pasture renewal were retained for further processing. The time series of imagery was then used to determine when/if these paddocks became bare and for how long. These values are included in the data set for each paddock mapped. The mapping process is described more fully in the report published along with this data set : Belliss et al, 2019, Identification of high-risk agricultural activities: national mapping of the location, scale and extent of winter forage cropping and intensive grazing on hill country land, contract report LC3469 prepared for the Ministry for the Environment. A description of the attributes for this data set and their values can be found in Table 9 on page 31 of this report. The 'BSP' attributes included in the attribute table each represent an individual satellite image scene with the attribute values denoting the proportion of bare ground observed in that scene. A value of 0 indicated that that the paddock was visible in the scene but there was no bare ground. A value of 9999 indicates that the paddock was not visible in that scene.