Estimation of forest stem volume using optical SPOT-5 satellite and laser data in combination

In this paper, the accuracy of forest stem volume estimation using a combination of optical SPOT-5 satellite and TopEye laser scanner data is investigated, at stand level. It is anticipated that the accuracy will be improved for the combined stem volume estimate compared to using SPOT-5 data only. The test site is located in the south of Sweden and consists mainly of coniferous forest. The stem volume for the selected stands was in the range of 30-620 m³ ha^-1 with an average stem volume of 288 m³ ha^-1 and an average size of 2.9 ha. Regression analysis has been used to develop stem volume functions for each sensor and for the combination. In the combined stem volume function the horizontal forest structure is captured by the optical satellite data whereas the vertical structure is represented by the laser derived tree height data. The accuracy in terms of relative root mean square error was 30.8% of the average stem volume for SPOT-5 and 15.7% for the combination. Thus, compared to using only SPOT-5 data the improvement was found to be 49% The result implies that the combination of multi-spectral optical satellite and laser derived tree height data can be used for standwise stem volume estimation in forestry applications.