The key technology of electronic guide system based on GPS and PDA

0 Introduction The maturation and development of GPS technology provide a powerful guarantee for the precise and real-time positioning of all kinds of moving vectors. such as the use of GPs to the vehicle or ship navigation and monitoring [2]. At the same time, with the development of information technology, the size of PDA becomes more and more compact, and the function of integration becomes more and more powerful. PDA is moving toward computing, communication, networking, storage, entertainment, E-commerce and other multi-functional integration trend of development [3]. At present, the combination of GPS and PDA advantages of the application development is still very little, although there are some application examples [4], such as in the GIs field, PDA and GPS in the field survey, but their application potential is far from being excavated. Based on the advantages of GPS and PDA, this paper puts forward a solution of universal flexible Electronic Guide system, discusses the key technologies of system design, including: the mapping of PDA electronic map, the best path search of electronic map and the matching of electronic map. These key technologies have been successfully applied and realized in Kunming World Horticultural Expo Park. 1 System Design 1.1 Principle and function of system design Electronic guide system is based on a GPS, PDA and GIS integrated application, is to use the powerful functions of PDA processing GPS real-time received data, combined with electronic map to achieve a variety of functions. In the electronic Guide system, the PDA organizes and manages various data and information of the tourist attractions, and establishes the topological relation to the road network, in order to realize the information query and the best path choice of the scenic spots, and use the GPS to carry on the real-time localization, and using the correlation algorithm to match the data received by GPs with the electronic map, To achieve the goal of precise positioning, the ultimate realization of the user needs of the function. The composition of the system is shown in Figure 1. The electronic guide system should be able to provide the following functions: Map settings, browsing, scaling, based on the real-time positioning of electronic maps and display on the electronic map, through the electronic map to search all the location of the site details of the user's current position to other locations of information inquiries, guidance function, timely pointed out the direction of the family; accurate time and date information Shortest path search, to provide users with one scenic spot to the best path to another scenic spot; key words find the details of the sights and their location on the map. 1.2 Key Technologies The key technologies to realize these functions are as follows: (1) How to use GPS and PDA to collect the coordinates of the scenic spot and realize the automatic drawing of the electronic map on this basis. If there is a datum receiver and a user receiver, a very precise coordinate can be obtained by using the principle of difference, because the system uses the single GPS receiver for coordinate collection, in order to ensure its accuracy, the control strategy of the coordinate precision factor and the satellite visible number is introduced on the basis of error analysis. (2) How to get the best route between any two spots in the scenic spot and display it on the electronic map. According to the number of scenic spots and the distribution of different types of different algorithms can be used. Because this system is Kunming World Horticultural Expo Park as an example of development, according to the characteristics of the scale and distribution of scenic spots in Kunming World Horticultural Expo Park, the algorithm is optimized by changing the judgment standard of the next node, and improves the efficiency of the algorithm based on the analysis of classical Dijkstra algorithm. (3) How to match the data received by the GPS receiver with the electronic map on the PDA. The map matching algorithm uses the High precision road information in the electronic map Library as the classification template to identify the pattern, and corrects the positioning error of GPs receiving data according to the recognition result. The specific matching algorithm used in the proposed electronic guide system is to use the historical walking trajectory to identify the road segment information in the electronic map library in real time mode. The following is a detailed introduction to these key technologies. 2 Mapping of electronic maps Because of the error of GPS positioning signal, the error of the data collected is analyzed and the control strategy is put forward, based on which the collected data is screened and processed, and the effective data is used to draw the electronic map. 2.1 Error analysis and control strategy Using single GPS receiver to collect coordinates, in order to ensure the accuracy of the map within a certain range, the coordinate precision factor (HDOP) and the satellite visible number (VIEW) are introduced to control the coordinates. Hdop is used to characterize the degree of drift in the horizontal direction of the measured longitude and latitude values. Foreign research experiments show that the relationship between 5,6],hdop, view and distance error is as follows: The larger the HDOP, the greater the distance error; the more view, the smaller the HDOP. In the experiment, a fixed point for the continuous acquisition of a large number of coordinate data, then the hdop=1.0 of all the coordinates of the calculated average as the actual coordinates, and then calculate the coordinates to the actual coordinates of the distance, the statistical results as table 1. Table 1 Statistics of HDOP, satellite numbers and error results ---------------------------------------------------------------- Hdop VIEW (AV) ERROR (AV) ---------------------------------------------------------------- 1.0 5.61342544854609 4.352385853 2.0 4.28216704288939 5.41197034058462 3.0 4.36612021857924 6.46000185103297 4.0 4.000 12. 93385468757 ---------------------------------------------------------------- Using linear regression analysis method can be obtained: error=2.679243 hdop+0.59144, as long as the value of Hdop control in (0~3.0) between the error can be controlled (0~11m) between (confidence level is 0.95), under the control conditions, mining point, In order to improve the accuracy of the point coordinate, the arithmetic mean value of the point coordinate can be obtained by increasing the number of the coordinates of the point. 2.2 Collection of data The process includes the field acquisition of coordinates (using GPS receivers to collect coordinates) and the collection of various descriptive materials, measuring materials, and text-picture materials of various landscapes in Kunming World Horticultural Expo Park. (1) The collection of coordinates The task of drawing a map is mainly to draw a panoramic map of the Kunming World Horticultural Expo Park, which is a marker of relative position for the main buildings, roads and parks of the park, according to the different characteristics of the entity, adopting different acquisition strategies, as follows: Building: Rules, collecting only a few inflection points of data; irregular, increase the number of positions in the contour of the collection of coordinates Road: Straight line, respectively at the intersection of the road and the inflection point of the collection of coordinate data, the curve, "straight generation" and at each bend at a certain distance of the continuous mining point, and these mining points in order to connect into a straight line. Closed Park: For some of the edge is closed curve of the park scenic spots, on the edge of discrete mining points, and then connected. (2) Collection of other Related materials Organize and process the data of related materials, and input the useful data into the relevant database according to the unified format. The collected coordinate data are collated and designed into a coordinate database, which mainly provides the coordinates of various scenic spots, roads and parks for automatic generation of algorithm calls, and is the main data source for generating electronic maps. For other data, such as the details of the various attractions, design a database of attribute information for use in the PDA query. 2.3 Using MapInfo GIS to realize electronic map After the collection of coordinates and related data, the data are imported into the database in the form of tables to complete the establishment of the database. Then use MapInfo GIS through ODBC or ADO and Kunming World Horticultural Expo coordinate database connection, citing the data, using Mapbasic programming to realize Kunming World Horticultural Expo Map of the electronic map. If the data in the database has changed, the algorithm can redraw the map in a timely manner. A vector model is used to make the whole electronic map, and the final map is the vector map. Different features are used to display different layers, such as scenic spots, road floors, park floors and so on. The map should include the map name, legend and so on. Finally, we should choose the right map symbol to represent the objects, so that we can express the features of the objects visually and vividly. The application of Mapbasic programming to the Kunming World Horticultural Expo Park electronic map divided into: attractions layer, road layer, regional layer, etc. to show that the purpose of this design is to better map editing and maintenance changes. The display effect of the road layer and the attraction layer of the electronic map realized by the above design idea and method is as shown in Fig. 2 and Fig. 3 respectively. 2.4 Re-editing of the map Since the resulting electronic map may be different from the actual layout, it is necessary to use Mapinfogis to edit the map, if it involves the modification of database related data, but also with the database to modify. Edit-generated maps can be completed by graphic editing and callout editing. Graphic editing: The main task is to modify the spatial location of geographical elements. Annotation edit: Add, delete, move callout, and the content of the annotation, font, color modification. The above road layer, the attraction layer and the park layer are edited and superimposed, the final drawing of the electronic map display effect as shown in Figure 4. 3 Search for the best path In order to achieve the best path of the electronic map search. Its storage topology must be designed with the idea of graph theory. The network is abstracted as a graph in the field of mathematics and computer, so it is based on the storage representation of the graph. Establishment of topological relation of 3.1 road network In the mathematical model of road network, it is necessary to use node and node and the connectivity of the road, that is, node and node and the topological relationship between segments. and the node of this kind of data is numbered according to the requirement of the best path algorithm. Because the operating platform of the system is the Windows CE on PDA, it is necessary to consider the time complexity and space complexity, so we need to optimize the classical Dijkstra algorithm from the time and space angle. After analysis, the Kunming World Horticultural Expo Park electronic map intersection of less than 100, for the non-weighted graph, so the adjacency matrix of the storage structure. Because it is a free weighted graph and the adjacency matrix is a symmetric matrix, a one-dimensional array can be used to store its lower triangular matrix to store the graph structure. Fig. 5 The Chinese block point represents the location of the scenic spot, the dot represents the turning point of the road, the line between the points and the point represents the road, and the segment distance represents the weight. All points are uniformly numbered and do not distinguish between these points when seeking the best path, except that the source and end points are only possible blocks (attractions). 3.2 Search for the best path Based on the analysis of the Dijkstra algorithm in classical graph theory, the algorithm avoids the calculation of unrelated nodes by changing the criterion of the next node. The blindness of classical Dijkstra algorithm is improved, the number of intermediate points is reduced and the search efficiency is improved. Dijkstra algorithm: It marks the node as a temporary T-label point into the T set and the final selected P-labeled point, the starting point is taken as the first P-label point (and released from the T set), and then the P-label point in the T-label point is selected individually by the principle of the shortest path, and it is put into the p set from the T set ( P is the set of nodes of the shortest path that has been obtained, and the initial value is empty until the target point (or all the points) is labeled as P-label point. The P-labeled point sequence from the starting point to the end point represents the optimal path. Dijkstra directional optimization algorithm: On the basis of the Dijkstra algorithm, using the principle of the shortest line distance between two points, when selecting the middle point between the source and the end point, only select the nearest point from the end line to join the P set. 1) Model Establishment In the Kunming World Horticultural Expo Park weighting Figure g, the weight represents the length of the side between two points, in the two designated vertices u0 and v0 to find a shortest distance path problem of the network model has the following characteristics: (1) The coordinates of the vertex u in Fig g can be expressed as (Xu,yu). (2) The shortest line between two points, the straight distance of any two point u,v in Fig G is recorded as: J (U,v) = ((XU-XV) (YU-YV) 2)-2 and J (u,v) <=d (u,v), where D (u,v) represents the weights from the U point to the V point. Set the distance from the shortest path that has been u0 to the UI, identified as L (UI), then u0 the minimum distance to reach V0 via UI should be L (UI) +j (Ui,v0). 2) algorithm Description (1) u0 is the starting point, every time the L (v) value of the vertex v is computed (v∈t), and the line distance between V and the target v0 is calculated (V,v0), and the lower limit of the distance from the u0 through V to V0 is considered as L (v) +j (v,v0). (2) The rules for adding a vertex to a P set in T are: Look for a bit of UI in the set T, from u0 the lower limit of the distance through the UI to the minimum, that is, satisfy: L (UI) +j (ui,v0) =min{l (v) +j (V,v0)} (v∈t), the vertex UI (ui∈t) is added to the set p. Kunming World Horticultural Expo Park Tourism, mainly walking tour, so in the road network, the shortest distance from the source point to the destination path is the best path standard. 4 GPS coordinates and electronic map matching As the GPS collection of Kunming World Horticultural Expo Park coordinates data map, there are certain errors, and when users use the Kunming World Horticultural Expo Park Electronic guide system for real-time positioning, also because of the weather, The surrounding building block and some other electrical signals interfere with the GPS signal so that the data received is inconsistent with the drawing of the Kunming World Horticultural Expo plot, which leads to the electronic guide system of Kunming World Horticultural Expo Park not accurate and real-time positioning, in order to solve this problem, According to the electronic guide system of Kunming World Horticultural Expo Park, a map matching algorithm is proposed to match the data received by GPs in order to achieve the accurate and real-time positioning of the electronic guide system in Kunming World Horticultural Expo Park. Basic method: Using the historical walking trajectory to identify the road segment information of map database in real time mode. As a kind of sample to be matched, the walking trajectory curve takes the road curve on all roads near the track curve as a state template, and selects the template with the highest shape similarity as the matching result through the matching between the sample and the template. Using the weighted 2-D Euclidean distance, a sequential statistical method is used to increase the confidence of the matched degree of similarity measure function. When a section is identified, the current data is made a vertical projection of the section, and the deviation δv in the direction of the vertical section is calculated and corrected. The algorithm is based on the premise that each road in a map is linearly segmented into a straight line segment. The pattern recognition of each section is described, and the recognition result of the preceding sections is used as the recognition weight of the similarity measure function of the latter section. This makes full use of the correlation of the walking trajectory, and introduces the idea of fuzzy judgment, so that the identification is more reliable. This method needs less computational capacity and is suitable for implementation on embedded system. Algorithm: map matching algorithm every 1s call once, the use of historical accumulation of data and real-time data for pattern recognition and error correction, the algorithm is as follows: 1 to receive GPS data preprocessing, if the current positioning results obtained by GPS and the previous point of the location results of the distance greater than the walking speed limit (10km/h) multiplied by the time interval, it is considered to be gross error, with the results based on the constant calculation to replace. 2) The direction error of the section is rectified beforehand. 3 Identify the walking section according to the historical walking track. 4 The GPS error is decomposed into parallel road direction and vertical road direction, and the vertical road direction error is eliminated by electronic map. 5 When the GPS signal is lost, according to the nearest location and speed of visitors, to estimate the current position of visitors. 6 If the surrounding can not find a matching walking section, then use the original data received directly on the electronic map, without error correction. 5 Application Examples These methods have been successfully applied and implemented in Kunming World Horticultural Expo Park Electronic guide system. 5.1 System composition The system includes: PDA, GPS receiver, PC, GIS, operating system, Mapxmobile control, electronic map, Access database, Mapinfoprofessional, embeddedvisualc++, Embeddedvisualbasic and so on. 5.2 System implementation Kunming World Horticultural Expo Park Electronic guide System product hardware, as shown in Figure 6 by the PDA, GPS and GPS and PDA linked to the card folder. Kunming World Horticultural Expo Park Electronic guide system interface as shown in Figure 7 by the menu bar, toolbar and the main interface: Menu bar to achieve the system settings, scenic spots and the best path, and other functions; toolbar to achieve the map to enlarge, shrink, drag and restore functions; The main interface displays maps and other properties. 6 conclusion The electronic guide system based on GPS and PDA solves several key technical problems, such as the control strategy of coordinate acquisition error and the automatic drawing of electronic map, the optimization of the classical Dijkstra optimal path search algorithm and the electronic map matching. There are still some problems needing further improvement, such as enhancing the usability of the system, reliability, providing more humanized service (such as voice navigation) and further improving the accuracy of positioning, etc., in order to improve the application value and application field of the system, it is necessary to enhance the expansibility of the system. The future goal is to be able to easily realize the electronic guide system of the scenic spot with the support of the electronic map of the scenic area and the related database. Reference documents: [1] bolingd. MICROSOFTWINDOWSCE program Design [M]. Beijing: Peking University Press, 1999. [2] Li Deeren, et al. Design and implementation of vehicle navigation system based on GPS and GIS [J]. Journal of Wuhan University of Surveying and Mapping, 2000,25 (3). [3] Wang Conggang, Wangqingyun. Network application research based on PDA mobile customer [J]. Computer Application Research, 2002, (3). [4] Feng Baohong, et. 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Introduction: Wang Tao Chun (1979-), male, Anhui inactive person, graduate student, main research direction: Mobile computing, image-based rendering technology; J (1980-), male, Yunnan Yuxi, lecturer, main research direction: Electronic commerce, mobile computing; Zhang Xuejie (1965-), male, Kunming, Yunnan, Professor, Ph. D, the main research direction: High-performance Computing, reconfigurable Computing technology, embedded systems, data fusion, information security and computer network, e-government system; Diana (1968-), female, Kunming, Yunnan, Professor, PhD, the main research direction: Based on image rendering, virtual reality, image processing, Computer vision and Multimedia.