Difficulties with estimating city-wide urban forest cover change from national, remotely-sensed tree canopy maps
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Urban Ecosystems. 11:81-90.
Two datasets of percent urban tree canopy cover were compared. The first dataset was based on a 1991 AVHRR forest density map. The second was the US Geological Survey's National Land Cover Database (NLCD) 2001 sub-pixel tree canopy. A comparison of these two tree canopy layers was conducted in 36 census designated places of western New York State. Reference data generated by photo-interpreting the tree cover on 1994 and 2002 orthoimages were compared on a city-wide basis to estimates of the tree cover derived from the AVHRR and NLCD tree canopy maps. Comparison of the AVHRR-based estimate with the 1994 photo-interpreted reference showed low accuracy and high variability. The comparison between the NLCD-derived estimate and 2002 photo-interpreted values had higher accuracy but shows a consistent under prediction bias for all tree cover values. In comparing the two photo-interpreted reference sets, little actual change was detected for this study region. Assessing change using differences between the imagery-based AVHRR and NLCD urban tree cover datasets is shown to lead to erroneous results.
Keywordsurban tree canopy cover change detection accuracy assessment NLCD 2001 tree canopy cover AVHRR
Walton, Jeffrey T. 2008. Difficulties with estimating city-wide urban forest cover change from national, remotely-sensed tree canopy maps. Urban Ecosystems. 11:81-90.