The base impervious coverage layer for the Region was sourced from a LiDAR survey completed in August 2010. LiDAR is a remote sensing technology that uses laser and light refraction to image objects and terrain. The 2010 LiDAR analysis mapped the extent of hard and soft impervious cover in the Region. The cost of acquiring LiDAR data for the Region makes quadrennial LiDAR surveys infeasible. To assess change in impervious cover without the benefit of new LiDAR imagery, information collected from project permitting by TRPA and partners was used to determine added/new coverage. Land capability as defined in the 2007 soil survey was used as the primary unit to measure coverage in a land capability class, both because it was used in the 2011 Threshold Evaluation Report (TRPA, 2012b) and because it is more detailed than the 1974 Bailey report (Loftis, 2007). Information about coverage removed was provided by the CTC, NDSL and the Parcel Tracker.