The effects of temporal differences between map and ground data on map-assisted estimates of forest area and biomass

Table 1 Estimates of proportion forest area for Minnesota study area

Ground data year, t_grnd	Sample size	Simple random sampling estimators		Model-assisted regression (GREG) estimators (map year, t_map)
		Simple random sampling estimators		2002				2007
		\( {\widehat{\mu}}_{SRS} \)	SE	\( {\widehat{\mu}}_{init} \)	Bîas	\( {\widehat{\mu}}_{GREG} \)	SE	\( {\widehat{\mu}}_{init} \)	Bîas	\( {\widehat{\mu}}_{GREG} \)	SE
2000	252	0.709	0.028	0.643	−0.033	0.676	0.025	0.639	−0.019	0.659	0.025
2001	238	0.637	0.031	0.643	0.028	0.615	0.024	0.639	0.018	0.621	0.025
2002	249	0.721	0.028	0.643	−0.026	0.668	0.022	0.639	−0.022	0.661	0.022
2003	247	0.700	0.029	0.643	−0.044	0.687	0.023	0.639	−0.003	0.643	0.022
2004	245	0.679	0.030	0.643	0.002	0.641	0.024	0.639	0.006	0.633	0.023
2005	252	0.707	0.028	0.643	−0.020	0.673	0.025	0.639	−0.017	0.656	0.025
2006	238	0.662	0.030	0.643	0.002	0.641	0022	0.639	−0.007	0.647	0.023
2007	249	0.750	0.027	0.643	−0.055	0.698	0.020	0.639	−0.051	0.690	0.019
2008	247	0.749	0.028	0.643	−0.093	0.734	0.021	0.639	−0.022	0.692	0.021
2009	245	0.699	0.029	0.643	−0.018	0.661	0.023	0.639	−0.014	0.653	0.022

ISSN: 1297-966X