Application Of Positioning And Area Measurement With GPS Technologies To Forest Resources Inventory In Low-mid Mountains In Western Sicuan Province

The methods of forest resource inventory and the concept, composition and positioning theory of GPS were briefly presented in this paper, and overseas positioning study with GPS technologies in forest resource inventory and its application status quo were presented, too. On this basis, this paper mainly discussed the application of positioning and area measurement with GPS technologies to forest resource inventory.Total-station Lead measurement was taken as the standard mode in this thesis. Applying RTK, PDA GPS and forest compass to position and measure area, and comparing these experiment results with normal mode results, the positioning and area measurement error was gained to compare with three methods' precision. The influence of environment factors on positioning and area measurement was mainly studied in this thesis, which factors including slope, slope site, aspect, crown density, dominant tree species, weather, date, period of time and down lead distance. Analyzing the experiment data, this thesis explored the relationship between these factors and positioning and area measurement, to improve on techniques of forest resource inventory, to increase accuracy of area measurement and positioning forest resource inventory sample plot. Based on the forty-seven experiments of positioning and area measurement in the Tianquan river valley, the data were analysed by SPSS 10.0, and the conclusions were drawn as follows.(1) Of the three measurement methods, the RTK's positioning precision is the highest, which average error is 4.44 meters. The next one is PDA GPS, which average error is 8.29 meters. The compass's positioning precision is the lowest, which average error is 13.43 meters.(2) The influence of slope site, slope and aspect on RTK and PDA GPS's positioning precision is not remarkable.(3) The influence of stand crown density on RTK and PDA GPS's positioning precision is remarkable. With increasing stand crown density grade, RTK's positioning precision error is 3.517 meters, 4.866 meters and 7.533 meters, and the PDA GPS's one is 3.352 meters, 7.162 meters and 10.914 meters. It is indicated that the relationship between positioning precision and crown density is the inverse ratio.(4) The influence of weather on RTK and PDA GPS's positioning precision is remarkable. Positioning precision in a rainy day is high, the average error of RTK is 2.139 meters and PDA GPS 5.510 meters. Positioning precision in Sunshine day is next one, theaverage error of RTK is 4.465 meters and PDA GPS 8.852 meters. Positioning precision in fog day is the lowest, the average error of RTK is 6.660 meters and PDA GPS 10.320 meters.(5) Results in this thesis indicate that the influence of dominant tree species on RTK and PDA GPS's positioning precision is remarkable. Positioning precision is the highest in longpeduncled alder stand. The next one is in the China fir stand. The positioning precision is the lowest in the hardwoods trees and Chinese cedar stand.(6) The influence of distance between RTK's move station and benchmark station on positioning precision is not of evidence.(7) About area measurement, RTK's precision is the highest, which average error is 1.747%. The compass takes second place, which average error is 3.87%. PDA's precision is the lowest, which average error is 5.039%. In addition, the study also indicates that the precision of area measurement in the non-stocked land is higher than that in the forest land when the other conditions are the sameness.At last application of GPS's positioning and area measurement in the forest resource inventory was discussed and prospected.