Tree Canopy Change, 2009-2014, Montgomery County, MD

This layer is a high-resolution tree canopy change-detection layer for Montgomery County, Maryland. It contains three tree-canopy classes for the period 2009-2014: (1) No Change; (2) Gain; and (3) Loss. It was created by extracting tree canopy from an existing high-resolution land-cover map for 2009 and a high resolution tree canopy map for 2014 and then comparing the mapped trees directly. Tree canopy that existed during both time periods was assigned to the No Change category while trees removed by development, storms, or disease were assigned to the Loss class. Trees planted during the interval were assigned to the Gain category, as were the edges of existing trees that expanded noticeably. Direct comparison was possible because both the 2009 and 2014 maps were created using object-based image analysis (OBIA) and included similar source datasets (LiDAR-derived surface models, multispectral imagery, and thematic GIS inputs). No accuracy assessment was conducted, but the dataset was subjected to thorough manual review and correction.