The possibility of autonomous detection of tree position with GPS for the need of early apple yield forecast

The accuracy of different GPS devices for precise sampling of trees needed for early yield forecast was studied in two years campaign. The precise positioning is fundamental for the comparison of yields between different years. In our experiment we used GPS devices MarchII, ASUS P565 and Nokia 5800 XpressMusic, which represented different precision and price ranges. To determine the positions and their accuracy, 245 randomly trees were selected from 245 orchards. We found out that the measurements made with MARCH II deviated to a diagonal for 16,72 m (X for 11,41 m and Y for 10,56m). Measurements made with ASUS P565 deviated in diagonal for 15,41m (X for 3,48 m, Y for 13,85 m). Nokia 5800 XpressMusic showed the highest deviation of 46,14 m in diagonal (X for 11,36 m, Y for 39,6 m). From the comparison of individual devices we have found out, that ASUS P565 as the best deviated in diagonal only for 1,31 m from MARCH II, but there was no significant difference. Despite the fact that discrepancies in individual trees is in particular measurement minimal (0,33 m), these devices are not yet precise sufficiently to be unequivocally identified with the position of sample trees.