Abstract:Low accuracy and poor effect are the main problems left over from the use of traditional information collection methods in fixed-point surveying and mapping data collection in the past. Since the introduction of the fixed-point surveying and mapping collection method of all-digital photogrammetry combined with GPS, the accuracy and effectiveness of fixed-point surveying and mapping data collection have been significantly improved. Real-time positioning is the basis for promoting the real-time collection of surveying and mapping fixed-point information. After many experiments and comparisons by the authors, the method described in this article can effectively improve the accuracy of real-time acquisition of fixed-point mapping data.
Keywords: gps all-digital photogrammetry GLOBAL POSITIONING system real-time acquisition mapping editing processing software
The industry not only needs theoretical knowledge but also technical support, the theoretical support and technical support of the geographic information industry comes from the scientific theory of surveying and mapping and modern surveying and mapping technology; and the data of information technology gps is mainly derived from all-digital photogrammetry; the data of geographic information system database and terrain database is mainly derived from the digital collection of aerial photogrammetry, the digital collection of all-field digital collection and digital collection of existing drawings [1]. High accuracy, fast mapping and low production costs are the three advantages of all-digital photogrammetry data acquisition in some areas with aerial photography data. Therefore, this paper focuses on the real-time collection method of surveying and mapping fixed point information under all-digital photogrammetry from multiple aspects and multiple angles, and further improves the efficiency and quality of real-time acquisition of surveying and mapping fixed point information.
1. Real-time acquisition method of surveying and mapping fixed-point information under all-digital photogrammetry
1.1 Real-time positioning of surveying and mapping fixed-point information
The real-time positioning of surveying and mapping fixed point information is the core of the real-time acquisition method of surveying and mapping fixed point information under all-digital photogrammetry. Establishing a stereoscopic model in the empty three-encrypted area as required needs to be completed before the implementation of real-time positioning of surveying and mapping fixed-point information. When the orientation is over, you need to enter some specific basic parameters in this model, including: the map scale parameter, the frame outline coordinates, and the map window.
Compiling different attribute codes for different targets (or features) can better help the geographic information obtained from the measurement to form identifiable data and save it. Usually the symbol library of the all-digital photogrammetry system is fully in line with the unified provisions of the state, in order to meet the needs of different users, for some special cases, the symbol library of the all-digital photogrammetry system can be appropriately supplemented (or modified) the required code or symbol. Of course, before measuring a feature, it is necessary to enter the new attribute code corresponding to the feature, or according to the options in the menu bar of the symbol library, the same type of figure data collection is carried out in order, and the different features are measured separately before entering the corresponding new feature code. In order to determine its fixed-point information, it is also necessary to measure each point of the feature in turn for recorded points or to track the contours, landforms and streamlines of the figure. In order to achieve the acquisition results of the final point recording, the user is also actively cooperating throughout the measurement process, and the given parameters are also a key part.
Errors can occur regardless of the system used, and all-digital photogrammetry systems are no exception, so it is necessary to set up error correction to take online editing measures, such as basic remedies such as additions, deletions, and modifications. At the same time, the utilization rate of the mapping system is set as the initial goal of the online editing measure, and in order to facilitate the information collection and supervision work at any time in the future, the measured data must be displayed in the stereo model. However, through eaves correction, copying, offset, etc., it is possible to complete the overlap, crossover and parallel between the graphics and the elements. Among them, lap is particularly important, when there is a good lap, the subsequent editing tasks and information collection work will significantly reduce the difficulty.
1.2 Real-time collection of surveying and mapping fixed-point information
This paper mainly takes the dm642 embedded information real-time acquisition system as the research focus of the real-time acquisition method of mapping fixed-point information under all-digital photogrammetry, and the hard disk storage, main processor, fixed-point information acquisition and GPS information collection are the four important components of this system. The workflow of the real-time acquisition method of surveying and mapping fixed-point information under all-digital photogrammetry is generally divided into three stages: (1) the information acquisition function is mainly derived from the camera, and the main processing module receives all the digital signals converted by tvp5150; (2) the GPS technology is selected when collecting the signal, and the GPS signal is transmitted to the main processing module, where the tl16c752b chip is selected to transmit the GPS information acquisition module. At the same time, the main processing module after receiving the digital information signal should immediately do compression coding processing, quickly and accurately extract the parameter information in the GPS signal; (3) the signal encoding data and the GPS latitude and longitude signal are interpolated and matched, and after the matching is successful, the locatable information is set to complete, and finally the local hard disk is used to save it.
The multi-task and tedious task is a feature of the real-time acquisition method of mapping fixed-point information under all-digital photogrammetry, so the rf5 structure is set as the basis of the application layer. Rf5 as a case of integrated large-scale architecture for reference, the main intention of using rf5 here is that it can solve the problem of many tasks and cumbersome tasks, the use of task thread blocking technology to scom for information transmission between tasks, such as audio video, network communication this kind of task relatively more program is the most suitable.
1.3 Matching between mapping fixed-point information and video images
In the process of matching the surveying and mapping fixed-point information with the video image, it is found that because the number of gps signals received is much lower than the number of frames collected by the information, the frequency of receiving gps signals and information acquisition is very different, which ultimately leads to the inaccurate docking of information GPS positioning and information acquisition. It is precisely for this reason that in the real-time acquisition method of mapping fixed point information under all-digital photogrammetry, the interpolated method will be selected to implement the matching of information collection and GPS positioning information.
The stationary mode and the driving mode are two matching methods for information acquisition and GPS positioning information in the real-time acquisition method of mapping fixed-point information under all-digital photogrammetry. The stationary mode is generally divided into two kinds: fixed point information collection and low-speed walking information collection, and the spatial position of this mode will only change slightly or be in a static state, so it is judged that the gps positioning value of the data information collected in this state is the same. Then the driving mode is a state that is completely opposite to the stationary mode, and the spatial position will change significantly or move rapidly. The GPS information data collected in this state is much larger than in the stationary mode due to the large change in spatial position but the interval time is very short.
1.4 Real-time editing of surveying and mapping fixed point information
The most commonly used method for mapping fixed-point information in real-time acquisition under all-digital photogrammetry is mape-dit editing processing software. Usually, the most commonly used in real-time information collection is when files in the dxf format. It can be seen that the choice to use mapedit editing processing software can more quickly and effectively improve the overall quality of real-time information acquisition and editing and its work efficiency. At the same time, other related data editing and processing work after the end of information collection can also be completed by mapedit editing and processing software. When faced with mountainous terrain, mapedit editing software can play its own unique advantages.
In the actual application process, mapedit editing and processing software and Southern Cass editing software are combined and used together, and the quality and work efficiency of information data editing have been improved again. In practice, mapedit editing and processing software is generally only responsible for editing contours, while southern cass editing software is an auxiliary editing of feature information, and when they each play their own unique advantages to complete their own content, they can be perfectly combined to effectively shorten the operation period [4].
Table 1 Experimental Survey Data Sheet Download the original table
Table 1 Experimental survey data sheet
2. Analyze through experimental demonstration
In order to prove that the real-time acquisition method of surveying and mapping fixed-point information under all-digital photogrammetry proposed in this paper has its application value in practical work, the author chose to compare the real-time acquisition method of surveying and mapping fixed-point information under all-digital photogrammetry with the real-time collection method of traditional surveying and mapping fixed-point information, and the specific experimental data is shown in Table 1.
Experiments have proved that the real-time acquisition method of surveying and mapping fixed-point information under the same conditions is significantly lower than the traditional surveying and mapping fixed-point information real-time collection method, whether it is medium error, coarse difference, coarse difference, or coarse difference rate, so its application value is still very high.
3. Concluding remarks
In summary, the fixed-point mapping data acquisition method advocated by all-digital photogrammetry combined with GPS advocated in this paper not only improves the efficiency and quality of real-time information collection, but also successfully solves many difficulties that traditional information collection methods cannot overcome. Among them, in the process of using mapedit editing and processing software, the choice of using the southern CASs editing software also improves the work efficiency and quality of information data editing, and is a good technology worth promoting and applying and learning, hoping that the industry will make full use of it in practical work, and also contribute to the development of science.