The Analysis Of Spatial Data Precision On The Land Consolidation

The precision of spatial data is an increasing concern over quantification about land consolidation. There are some impending problems on quantified description of land consolidation using "3S" technology: (1) In many regions where the big scale is absent, how to resolve the problem about the geometric correction of the high precision remote sensing image; (2) the original data and the interpolating method are the two main factors that affect the precision of DEM, however, the spatial data has no true value, the problem is how to obtain the true value and to analyze the effect of the original data and interpolating method on the precision of earthwork; (3) when calculating the earthwork through DEM that are constructed by vectoring the relief map, how to improve the accuracy of the earthwork by advanced technology. Since the error is the inherent attribute of the spatial data, it can not be completely eliminate but to improve the data accuracy step by step. Therefore, it is of important significance to discuss the effect of different interpolating method, how to obtain the original data, and the sources of errors on the precision of data.In this study, firstly, the high resolution remote sensing image, which was geometrically corrected by the big scale relief map (1:500 and 1:2000), was taken as the foundation to analyze the correction precision of the high resolution remote sensing image that was geometrically corrected by the points of GPS. Secondly, two physical models were constructed, which could model rough surface and describe the features of the earth surface, such as chine, neck, valley and hill, etc. According to difference method, the "true" volume of the physical models were measured, which was 13260cm3 and regarded as the analysis foundation of the precision of the volume that was calculate by DEM. The discrete dada of the models on a regular spacing of 1cm were collected by 3SPACE FASTRAK and the DEM was obtained by interpolating the discrete dada through GIS software. Based on the volume of the models calculated by DEM, different interpolating methods (IDW, Spline, Natural Neighbor, and Kriging) and variation of grid spacing of data were compared and their effects on precision of volume calculation were analyzed. Some reference points were measured by the high precision GPS (RTK) to examine the precision of the DEM. The elevation difference between measured and interpolating data was used to construct the DEM and calculate the error of the volume. And then the precision of the earthwork could be improved.The results showed that: (1) some governing points, which were measured by submeter precision GPS, were utilized to correct the 1 m precision remote sensing image and it could satisfy the desired precision of geometrical correction, therefore, this method could be used as geometrical correction in the region where was short of the big scale relief map; (2) the density of the original data was the main factor to affect precision of the volume, and the precision of the calculated volume of earthwork could be improved to more than 90% when using the test points and feature points; the sparser the data density were, more significant could be improved; On the base that elevation of test points were measured by the submeter precision GPS, the error of the volume, which was produced by vectoring relief map toobtain DEM, could be calculated, and the calculation precision of the earthwork could be improved markedly.