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

Table 2 Estimates of mean biomass per unit area (Mg/ha) for the Våler study area

Ground data year, t_grnd	Stratum					Within stratum estimator
	Stratum			Simple random sampling estimators		Model-assisted regression (GREG) estimators (map year, t_map)
	Number	Weight	Sample size	\( {\widehat{\mu}}_{SRS} \)	SE	1999				2010
	Number	Weight	Sample size	\( {\widehat{\mu}}_{SRS} \)	SE	\( {\widehat{\mu}}_{init} \)	Bîas	\( {\widehat{\mu}}_{GREG} \)	SE	\( {\widehat{\mu}}_{init} \)	Bîas	\( {\widehat{\mu}}_{GREG} \)	SE
1999	1	0.126	31	49.21	6.96	48.84	0.16	48.69	2.18	112.86	66.77	46.09	5.37
	2	0.231	55	114.89	7.92	96.82	−0.02	96.84	2.17	143.77	55.92	87.85	6.03
	3	0.269	58	153.79	8.93	156.74	−0.11	156.85	4.46	124.83	−33.61	158.44	13.00
	4	0.374	32	94.59	6.73	92.23	−4.45	96.68	3.68	101.75	2.06	99.69	8.54
	All	1.000	176	109.47	3.89			106.84	1.78			105.98	4.85
2010	1	0.126	31	116.07	9.80	48.84	−66.70	115.55	6.03	112.86	−0.09	112.95	2.47
	2	0.231	55	171.23	11.98	96.82	−56.36	153.18	6.85	143.77	−0.42	144.18	3.67
	3	0.269	58	118.47	14.96	156.74	35.21	121.53	14.39	124.83	1.71	123.11	4.00
	4	0.374	32	95.77	9.20	92.23	−5.62	97.85	9.73	101.75	0.89	100.87	2.66
	All	1.000	176	121.87	6.22			119.24	5.42			118.38	1.75

ISSN: 1297-966X