LUCAS NZ Forest Clearing 2008-2020 v019

*Detection*
Image mosaics used for change detection are cloud-masked, orthorectified, corrected for atmospheric conditions, and reflectance standardised using the Ecosat algorithms documented in Dymond et al, (2001), Shepherd and Dymond (2003) and Dymond and Shepherd (2004).

In order to estimate rates of deforestation for a calendar year, two mosaics of multispectral satellite imagery with shortwave-Infrared bands (such as SPOT 5, Landsat 7, Landsat 8 and Sentinel 2) are compiled (from capture as near as possible to the beginning of January of Year A and Year B respectively). Matching spectral bands from the two mosaics are compared in a stack to detect change.

Manual quality control checking is performed to remove false-positives arising from small clouds or image mis-registration (Newsome et al, 2018).

A nominal year of clearing is automatically derived, but may receive manual correction during the land use intention classification stage.

*Classification*
Detection and classification of non-anthropogenic change is a by-product of attempting to find the directly anthropogenic (human-induced) change that is applicable to the LUCAS Land Use Map.

The determination that a change is non-anthropogenic is usually made by judging context and pattern visible in satellite imagery. However, when higher resolution aerial imagery becomes available following the clearing event, it can often be useful in confirming the classification.