大比例尺数字测图初探.doc

大比例尺数字测图初探
大比例尺数字测图初探

Li Fengli
Survey and Design Institute,Shan Xi Province
摘要：文章论述了大比例尺数字测图的特点、作业方法和基本作业过程, 提出测绘人员必须充分认识测绘技术发展的大势所趋,努力学习和提高自己。
关键词：大比例尺、数字测图、特点、作业方法、过程
1大比例尺数字测图概述
随着计算机技术的飞速发展,计算机在测绘领域中的应用也不断深入,大比例尺数字测图已成为测绘技术变革的一个重要内容。多种数据采集和处理方法的实现为大比例尺数字测图提供了条件,特别是电子手薄的出现, 无疑是测绘技术的一项革新,它不仅能够实现快速、简便野外数据采集,而且还能及时对采集的数据进行处理。由全站仪和电子记录手簿组成野外数据采集系统,记录的数据可直接传输给计算机, 在相应的程序系统下进行人机交互处理, 形成大比例尺地图图形数据。这种图形数据可以贮存在数据载体(如磁盘) 上,也可以用自动绘图仪绘成图。以数据形式贮存在数据载体上的大比例尺地图就是大比例尺数字地图。
1.1大比例尺数字地图的特点
大比例尺数字地图是以数字形式来表示地图的内容的,地图的内容由地图图形和文字注记两部分组成, 地图图形可以分解为点、线、面三种图形元素, 而点是其中最基本的图形元素。数字地图以数字坐标表示地物和地貌点的空间位置,以数字代码表示地形符号说明注记和地理名称注记。大比例尺数字地图能够精确地、真实地反映地表所包含的全部人工和自然的碎部要素。数字地图并不是依照某一固定比例尺和固定的图幅大小来贮存一幅地图的,它是以数字形式贮存的数字地图。根据不同的需要,在一定比例尺范围内可以输出各种比例尺和不同图幅大小的地图,输出各种分层叠合的专用地图。例如: 以地籍边界和建筑物、土地利用分类为主的地籍图; 以地下管线以及两侧建筑物为主的地下管线图等。大比例尺地面数字测图, 在野外采用全站仪测量, 具有较高的测量精度,按目前的测量技术, 地物点相对于邻近控制点的位置精度达到5cm是不困难的。用自动绘图仪依据数字地图绘制出的图解地图, 图面美观大方, 位置精度均匀。精度也高于手工绘制的地图。
1.2大比例尺数字地图的作业方法
大比例尺数字地图的制作主要分为三个阶段: 数据采集、数据处理和地图数据的输出。数据采集是在野外利用全站仪测量与记录仪器获取数据,这些数据要按照计算机能够接受的应用程序所规定的格式来记录。从采集的数据转化为地图数据,需要借助于计算机程序在人机交互方式下进行一定的处理,如坐标变换、地图符号的生成和注记的配置等, 这就是数据处理阶段。地图数据的输出也以数字方式进行。即把图形数据以数字形式贮存在图形文件中。在需要输出时以图解方式通过自动绘图仪绘制最终的地形图。大比例尺数字地图的建立在数据采集阶段可采用地图数字化方法和野外地面数字测图法。在没有合乎要求的大比例尺地图的地区,例如新开发的建成区, 或者是工程设计需要大比例尺数字地图的地区,可直接采用地面数字测图方法来绘制大比例尺数字地形图,这种方法也称为内外业一体化数字测图方法。在野外对地图上所有要表示的地形点进行测量并计算它们的精确坐标,并用代码给出各点的连接关系和地图符号信息,通过计算机程序处理, 建立数字地图。采用这种数字测图法建立的大比例尺数字地图精度相对比较高[1]。地图数字化方法是指直接在手工测量的图纸上得出各地物点的坐标,并将各地物点分类编码并标记其连接方式后输入到计算机程序,由计算机依据不同的编码和连接方式进行处理后绘制而成。
2大比例尺地面数字测图的基本作业过程
大比例尺地面数字测图的流程示意如图1。

图1大比例尺地面数字测图流程示意图
大比例尺地面数字测图分为数据采集、数据编码和计算机处理、自动绘制地图两个阶段。数据采集和编码是计算机绘图的基础,这一工作主要在外业期间完成。内业进行数据的图形处理,在人机交互方式下进行图形编辑, 生成绘图文件,最后由绘图仪绘制大比例尺地图。地面数字测图系统的基本硬件要求: 全站仪或测距仪、经纬仪; 电子记录手簿或掌上电脑;便携式计算机; 数字化仪; 微型计算机;打印机; 绘图仪等。软件系统要求有以下功能:碎部测量数据的图形处理;在交互式方式下的图形编辑; 等高线自动生成;地图数字化; 图形绘制。
2.1 外业工作
平板仪测图和经纬仪测图的地形原图基本都是在外业完成的,而地面数字测图的外业工作只需完成地图数据的采集和编码。测量工作主要包括图根控制测量、测站点增补和地形碎部点的测量工作。采用全站仪或者是测距经纬仪进行观测, 用电子手簿记录观测数据或经计算后的测点坐标。每一个碎部点的记录,通常有点号、观测值或坐标,除此以外还有与地图符号有关的符号码以及各点之间的连接关系码。这些信息码均以规定的数字代码表示。输入这些信息码极为重要,因为地面数字测图在计算机制图中自动绘制地图符号就是通过识别测量点的信息码执行相应的程序来完成的。信息码的输入可在地形碎部测量的同时进行,即观测每一碎部点后随即输入该点的信息码。地图上的地理名称及其它各种注记,除一部分根据信息码由计算机自动处理外,不能自动注记的需要在草图上注明,在内业通过人机交互编辑进行注记。常规的地形测图工作要求对照实地绘制, 而数字测图记录的数字很难在实地进行巡视检查。为克服数字测图记录的不直观性,在观测数据编码后, 可用便携机显示图形,对照草图检查。更好的办法是用简易绘图仪绘制工作图,用以外业巡视检查,是否有漏测, 地物符号和地貌表示是否与实地一致。特别是在作业地点远离内业地点的情况下,必须有一定的措施对记录数据和编码进行检查,以保证内业工作的顺利进行[2]。
2.2 数据处理和图形文件生成
数据处理是大比例尺数字测图的一个重要环节, 它直接影响最后输出的图解的图面质量和数字地图在数据库中的管理,外业记录的原始数据经计算机数据处理后, 生成图块文件, 在计算机屏幕上显示图形。然后在人机交互方式下进行地图的编辑,生成数字地图的图形文件。数据处理分数据预处理、地物点的图形处理和地貌点的等高线处理。数据预处理是对原始记录数据作检查, 删除已作废除标记的记录和删去与图形生成无关的记录, 补充碎部点的坐标计算和修改有错误的信息码。数据预处理后生成点文件。点文件以点为记录单元,记录内容是点号、符号码、点之间的连接关系码和点坐标。地物点的图形处理是指计算机根据不同地物点的类型和连接方法, 把各地物点连接进来形成图形, 并标注对应的标记[3]。最后经过地貌点的等高线处理就形成了数字化地图。
2. 3地图和测量成果报表的输出
人机交互编辑形成的数字地图图形文件可以用磁盘贮存和通过自动绘图仪绘制地图。微机制图一般采用联机方式, 将计算机和绘图仪直接连接,计算机处理后的数据和绘图指令送往绘图仪绘图[4]。绘图过程中,计算机的数据处理和图形的屏幕显示处理基本相同。但由于绘图仪有它本身的坐标系和绘图单位, 因此需将图形文件中的测量坐标转换成绘图仪的坐标。打印机是测量成果报表的输出设备。此外, 打印机也可以打印图形,这时将打印机设置为图形工作方式[5]。打印机绘制的图形精度比较低,只是一种粗略的图解显示,一般仅用于对图形进行核对和检查。
3结束语
随着科学技术的不断发展,推动着测绘业也在发生着巨大的变化。测绘技术与计算机技术的紧密结合、测绘的数字化已成为大势所趋。应该清醒地认识到这一点, 随着计算机和电脑蕊片技术的日新月异,今后类似电子手簿的新产品必将不断涌现,其功能也将会日益强大和完善, 这必将推动测绘业在不远的将来发生革命性的变化, 这对于从事测绘工作的青年人来说,既是挑战, 更是一次难得的历史机遇, 应当从现在起就要努力学习新的科学技术,尤其要观注计算机在测绘领域的新技术和新产品, 不断提高自身的业务和技术素质, 紧紧把握住时代的脉搏,为测绘事业的早日腾飞尽一份力。
参考文献
[1] GB/T13977-92, 1:5000 1:10000 Topographic Map Aerial Photography Measurement Field Work Specification[S].Beijing:China Standard Press, 1992,pp.1-23.
[2] GB/T13990-92, 1:5000 1:10000 Topographic Map Aerial Photography Measurement Indoor Work Specification[S].Beijing:China Standard Press, 1992,pp.8-15.
[3] GB/T19711-2005, Navigation Geographical Data Model and Exchange Format [S]. Beijing:China Standard Press, 2005,pp.1-8.
[4]GB/T20268-2006,Vehicle-bone Navigation Geographical Data Acquisition and Processing Technology Specification [S].Beijing:China Standard Press, 2006,pp.2-10.
[5] GB/T 20257.2-2006, National Basic Scale Cartographic Symbols Part II: 1:5000 1:10000 Cartographic Map Symbols [S]. Beijing: China Standard Press,2006,pp.4-56.

Probe into Digital Mapping with Large Scale Ratio
Li Fengli,Survey and Design Institute,Shan Xi Province
ABSTRACT
This paper probes into the features, operation methods and basic operation courses of the digital mapping with large scale ratio, and points out that the plot observers must know well the developing trends of the mapping technique and make great efforts to learn the new techniques and improve themselves.
KEYWORDS:large scale ratio; digit; mapping
1. Summary of digital mapping with large scale ratio
With the rapid development of computer technology, computer application in the field of Surveying and mapping also unceasingly thorough, the large scale digital mapping has become an important content of Surveying and mapping technology change. To achieve a variety of data acquisition and processing method provides the conditions for the large scale digital mapping, especially thin electronic hand appear, is undoubtedly an innovation technology of Surveying and mapping, it not only can realize fast, simple field data collection, but also to the collection of data processing. Field data acquisition system composed of total station instrument and electronic notebook, the recorded data can be directly transmitted to the computer, interactive processing machine in the corresponding program system, the formation of large scale map graphic data. This graphic data can be stored in the data carrier ( such as a disk ), can also be used as graph plotter. With the data stored in large scale map data carrier is a large scale digital map.
1.1 Characteristics of large scale digital map
Large scale digital map is in digital form to represent the content of the map, map elements from the map graphics and text annotation is composed of two parts, the map graphics can be decomposed into point, line, surface of three kinds of graphic elements, and is one of the most basic graphic elements. The digital map to digital coordinate representation of spatial location and landscape features of the digital code, said topographic symbol annotation and geographic name note. Large scale digital map can accurately, reflect the surface contains all of the artificial and natural broken element. The digital map is not in accordance with a certain scale and the fixed size of maps to store a map, it is digital map stored in digital form. According to different needs, can output various scales and different drawing size map in a certain scale range, the output of various kinds of special maps superimposed layering. For example : the main cadastral boundaries and building, land use classification of cadastral map; mainly in the underground pipeline and on both sides of the building underground pipeline map. Large scale digital surveying and mapping, by total station instrument in the field, and it has higher measuring precision, according to the current measurement technique, feature point position accuracy relative to adjacent control points to 5cm is not difficult. Graphical map drawn by automatic plotter based on digital map, surface appearance, position precision uniform. Precision is also higher than the manual map.
1.2 Operation methods of large scale digital map
Production of large scale digital map is divided into three stages: the data acquisition, data processing and map data. Data acquisition is the total station measuring and recording instrument used in field data acquisition, these data are required by the application of computer to accept the format to record. The transformation from the collected data into map data, with the aid of computer program in interactive mode of processing, such as generating and coordinates transformation, map symbol memory configuration, this is the stage of data processing. The output map data were also digitally. That the graphic data in digital form stored in a graphic file. In need of output in graphic mode automatic plotter through the final topographic map. A large scale digital map in the data acquisition stage can adopt the method of map digitization and field digital surveying and mapping method. In a large scale map is not in line with the requirements of the region, such as the development of new districts, or the need of engineering design for large scale digital map of the area, can be used directly on the ground digital mapping method of large scale digital topographic map to draw, this method also known as internal and external integration of digital mapping method. In the field of the map all to represent terrain points were measured and calculated the exact coordinates of them, and the code is connected and map symbol information of each point, by the computer program, the establishment of digital map. The digital measurement of large scale digital map accuracy of the relatively high. Method of map digitization is obtained directly from the point coordinates in the manual measurement of the drawings, and the points classification code and mark the connection pattern is input to the computer by the computer program, according to the different coding and connection processing painted.
2 Basic operating progress of terrestrial digital mapping with the large scale ratio
Schematic progress of the large scale digital surveying and mapping is as follows:
Portable machine

The total station instrument

Electric book

Computer

Software system

Digital instrument

Graph plotter

Printer

Figure1.The sketch map of Terrestrial digital mapping and surveying with large scale ratio
Large scale digital surveying and mapping is divided into data acquisition, data coding and computer processing, automatic mapping of two stages. Data acquisition and coding is the foundation of computer graphics, this work is mainly completed in the field during the. The basic hardware terrestrial digital mapping system requirements: total station or distance measuring instrument, electronic theodolite; notebook or palmtop computer; portable computer; digitizer; microcomputer; printer; plotter[1]. The software system has the following functions: detail processing of measurement data in an interactive mode graphics; the graphics editor; automatic contour generation; digital map; drawing.
2.1Outside work
Plane-table mapping and theodolite mapping topographic manuscript are basically completed in the field, and the digital surveying work outside the industry, the only need to complete the map data collection and coding. The measurement work mainly includes the measurement control measurements, the measurement site additions and terrain points. Using total station or observed ranging theodolite, data of electronic book recording observation or by measuring the coordinate calculation. Every detail point records, usually with dot, observations or coordinate, between besides relating to map symbol code as well as the points of connection code. These information code in digital code provisions of the said. Input the information code is very important, because the ground digital mapping automatic map symbols to complete through the information code recognition measurement point of the implementation of the corresponding procedure in computer graphics. Information code input can be carried out in the terrain measurement at the same time, namely the observing every detail point immediately after the input information of the point code. The map of the geographical names and other various notes, except for the part according to the information codes by computer automatic processing, can not automatically note note in the sketch, including the industry through interactive editing of notes. The conventional terrain mapping requires the control of field mapping, digital mapping record number is very difficult in the on-site inspection. In order to overcome the digital measurement is not intuitive chart, the observed data after coding, display graphics available portable machine, control sketch check. A better approach is to use simple plotter working drawings, used in industry inspection, whether there is leakage detection, symbol and geomorphology indicates whether consistent with field. Especially in the work place away from the location within the industry situation, there must be measures to check the record data and code, to ensure the smooth progress of industry[2].
2.2 Data processing and graphics files
Data processing is an important part of large scale digital mapping, it directly affects the final output management graphic picture quality and digital map in the database, and the original data recorded by the computer data processing, graph files, graphics are displayed on the computer screen. Then the map editor in the man-machine interactive mode, generating digital map graphic file. Contour processing data processing graphics and geomorphological point data pre-processing, feature point. Data preprocessing is to check the original records data, deleting irrelevant records and delete and drawing the abolition of labeled record has been made, additional detail point coordinate calculation and modification of information error code. After data preprocessing file generation point. Some files point to the recording unit records the contents, as the connection code and point coordinates of points, symbolic code, between point. Graphics processing feature point refers to the computer according to the different types of feature point and connecting method, put the point connection in pattern formation, and mark the corresponding markup[3]. After the final contour processing point on the formation of digital map.
2.3The output of map and mapping results
Digital map graphic file HCI editing form can use disk storage and mapping by automatic plotter. Computer graphics generally use the on-line mode, the computer and plotter directly connected, after computer processing data and drawing instruction to plotter[4]. The drawing process, computer data processing and graphical display treatment is basically the same. But because the plotter has its own coordinate system and the drawing unit, so the measurement coordinate graphics file conversion into plotter coordinates. The printer 's output device measurement results report. In addition, the printer can print graphics, then set the printer for graphics work[5]. Printer drawing accuracy is relatively low, only a rough graphic display, generally only for checking and examination of the graphics.
3 Conclusion
With the development of science and technology, promote the surveying and mapping industry is undergoing tremendous changes. Digital technology and computer technology of Surveying and mapping, surveying and mapping combination has become represent the general trend. Should be aware of this point, with the computer and the computer chip technology change rapidly, the future similar electronic hand book of new products will contin