Geodesia et Descriptio Terrarum (Geodezja i Kartografia) 9 (3) 2010
UNCERTAINTY OF SPATIAL DATA IN GEOGRAPHIC INFORMATION SYSTEMS (GIS)
uncertainty, model ling of spatial phenomena, GIS system
The complexity of the real world leads to a point where the image represented in the conceptual model in the form of spatial data cannot be made with any accuracy adopted. Recipient of knowledge, therefore, is accompanied by a sense of uncertainty, which may be either stochastic, directly related to the accuracy of the measurement described or cognitive, resulting from the incomplete knowledge of recipient of information and limited possibilities of making measurements with the desired accuracy, which may be characteristic for a statistical sample of the larger population of typical and reproducible objects represented in the model. A sense of uncertainty in the reception of geo-information is inextricably linked with the necessity of gradual simplification of representation of different spatial units to a form of image presented in the Geographic Information Systems (GIS). The article presents ways of defining the spatial data in the form of discrete objects and fields, using the vector and raster method, concepts of uncertainty associated with it, its types, methods of estimation, concepts of accuracy and precision of measurement and modeling techniques of described objects and spatial phenomena, referring both to the classical statistical analysis and probabilistic methods using the theory of fuzzy sets.
COMPARISON OF THE ELEVATION OBTAINED FROM ALS, ADS40 STEREOSCOPIC MEASUREMENTS AND GPS
Beata Hejmanowska, Artur Warchoł
ALS, Digital Terrain Model, vertical accuracy assessment, GSP RTK, ADS40
Research of the vertical accuracy assessments according different methods are in the paper presented. The following data were compared: GPS RTK (as a reference), air- borne stereo model from ADS40 camera, cloud of points from the ALS, and a GRID model created from the ALS data. Raw ALS data were initially preprocessed in TerraScan for classifying of ground points (using the active TIN model algorithm). Triangulations in a radius of 20 m around the GPS control points were performed. Then the height corresponding to GPS position (x, y) was from the triangle plane calculated. In the same way height for GPS position was obtained from ADS 40 stereo model. NMT in GRID model of 1 m grid size was generated in TerraScan basing on the points early classified as a ground. The lowest of the all data set was GPS surveying (average, more than 0.2 m below the ALS data). ALS points cloud and GRID model were the closest to each other but the NMT was an average of 0.1 m above the raw data.
the bling people, sonoring modelling, spatial questions, sonoric digitizer
Apart from wide applied touching models, sonoric modelling of spatial issues with application of sonoric digitizer is also possible. The essence of sonoric modelling is based on usage sequences of various sound signals as suitable for following points of the line creating contour notes. Regarding to the level of the intellectual development of a pupil in educational school process it is possible to single out three stages, responding to age levels. In Polish conditions in the first age level "integrated elementary school teaching" is accomplished. Beginning from fourth class, section of school subjects is leading in, and a third level is responding to gymnasium level. Estimating in three stages system of point marks, importance of issues connected with spatial topics in the joint educational program for visible, as well as for invisible pupils, summary valuation of spatial issues in particular school subjects and teaching stages has been obtained. The main section will be inertly extended presenting, in the final form, the separated system of school subjects from the range of primary school and gymnasium. It allows the application in school teaching the test responding to chosen issues during the realisation various subjects, which the issues are important in. Between over one hundred tests, prepared in the beginning stage of the implementation of the method, after the practical verification, the set of 23 educational tests has been executed. Wider usage the method in school practice is possible after elaborating thematically sets, responding to a particular discipline and educational levels.