Discussion on the solution of several important problems in topographic map editing-topographic map drawing steps

This paper briefly expounds the related knowledge of topographic map, introduces in detail the important methods, principles and matters needing attention in the process of editing and drawing topographic map, and introduces the related topographic map editing software, and also mentions the important application of topographic map in various fields.

Keywords: map topographic map topographic map editing

China Library Classification Number: TB23 Document Identification Number: A Document Number:1672-3791(2012) 05 (c)-0024-01.

As the most basic tool to express the spatial distribution, combination, connection, quantity and quality characteristics of various phenomena on the earth's surface and their development and changes in time, maps play an increasingly important role in national economic construction, national defense construction, scientific education and cultural education, and even navigation, traffic inquiry and tourism closely related to people's lives. Making topographic map is a complicated process. No matter which mapping method is adopted, the editing process of topographic map is essential. The quality of this process has a great influence on the drawing quality and future use. In a word, topographic map editing is the core work throughout the whole topographic map production process. How to edit a good map, so that map works can better serve social production and life? As a first-line surveying and mapping worker, I combine my own work experience to discuss and analyze several important issues in topographic map editing as follows.

1 Understand the basic knowledge of topographic maps.

1. 1 the concept of topographic map

To edit a topographic map, you must first have some topographic map knowledge, preferably professional knowledge, which is very important for editing a good map.

Topographic map is a kind of ordinary map, which is an orthographic projection map showing the plane position and elevation of landforms and features according to a certain proportion. Its basic features are as follows.

(1) Geodetic survey results can be used as the control basis of plane and elevation, and the longitude and latitude grids and rectangular coordinate networks can be printed, which can accurately represent the geographical position and landform characteristics of topographic elements.

(2) Field mapping with aerial photogrammetry or field investigation as the main means is detailed and accurate.

(3) Geomorphology is generally expressed by contour lines, which can reflect the actual height and undulating state of the ground, and has a certain three-dimensional sense, which can meet the needs of analyzing and studying the terrain on the map.

(4) Ground features generally represent natural and human elements, and are divided into independent ground features, residential areas, transportation networks (mainly land road networks), water systems, landforms, soil and vegetation, and boundary lines.

(5) There is a specified scale series.

(6) There are unified schematic symbols for easy identification and use.

In addition, in order to keep the topographic map up to date, it is also stipulated that it should be updated regularly.

1.2 Matters needing attention in graphic editing

(1) Get ready.

Before editing, you should first read the technical design book carefully to understand the background and details of the project in detail. Including the purpose of the project, data format, software selection, precision control in editing, time limit for project completion, etc. Each project may have its own special requirements. At this time, we should pay special attention to these, and we must not work only by experience, resulting in unnecessary rework.

(2) Deploy software and configure symbol library.

When editing topographic map, the software and data platform used are often different according to the requirements of each project, the purpose of the map and the requirements of data format. In the current environment, the topographic map produced by a project is no longer just for plotting, but for establishing a database, maintaining and reusing data. Therefore, in the choice of software, we should choose the data platform suitable for establishing the database as far as possible. This is also the direction of efforts of various production units in recent years.

To measure the standard of a drawing software, we must first look at whether the software is suitable for the actual situation of the unit; Secondly, it depends on its operability, whether the interface is friendly and easy to learn, etc. Finally, it depends on whether the function it provides is suitable for this unit.

At present, the software used by various surveying and mapping units can be described as varied and numerous. But basically, there are two kinds, one is a system (unit) developed by itself, and the other is developed by a special surveying and mapping software developer, which is provided to the majority of users for commercial purposes and is also used by various surveying and mapping units. Generally speaking, the selection of software includes the following aspects: according to the data source, according to the purpose of topographic map (database building, mapping requirements, or both), according to the data platform or data format required by Party A, and so on.

Our unit has been trying to constantly improve the configuration and selection of software. Now MapGis, Geway, MicroStation, AutoCAD, Antu series, ArcGis, CASS series and so on are mainly used.

In addition to using the software, tools and batch programs needed in this project, you can also use some software tools of similar projects in the past, and leave the work to the program as much as possible to reduce the workload and improve the editing efficiency.

Combined with the project "Anyang 1∶500 True Color Digital Aerial Survey Digital Mapping", the data editing requirements of topographic maps are discussed.

At the beginning of technical design, data editing rules must be formulated according to the characteristics of this scale digital topographic map, and various resource files must be compiled, including establishing template files, making public blocks, perfecting symbol library and line library, selecting unified font library, and formulating data hierarchy and coding. These tasks should be done in detail, such as the determination of some insightful object codes, and it is best to specify the layer code and bus data production method of each object.

2. 1 data editing

DLG editing is the most critical link that affects data production. The editing of digital topographic map has already broken the traditional concept of cartography, and should take into account both cartographic data and bus data, meet the requirements of CAD data conversion, and meet GIS industry standards in terms of mathematical benchmark (coordinate system), attribute accuracy, topological relationship and logic, metadata production, file naming and data format.

(1) data to meet the needs of cartography and database construction. The collection of all topographic map elements meets the basic requirements of spatial geographic data, which can be summarized as: lines should be connected, surfaces should be closed and points should be accurate.

(2) If polygon objects can be closed, they should be closed strictly; Polygons with common edges are strictly captured (snapped) at the intersection, and gaps and multiple overlaps are not allowed; The public edge is only collected once, and other layers are generated by copying. Polygons are not allowed to be represented by blocks.

(3) The linear object should be connected (that is, the acquisition should not be interrupted artificially. For example, it is not allowed to manually truncate the terrain elements just for the effect of plotting, and the software will complete the capping on the premise of keeping the terrain requirements complete); Different features must be captured reasonably according to the specifications, and unreasonable pause is not allowed; If special symbols are generated by programs, skeleton lines and skeleton information must be kept intact and coded correctly.

(4) The dot symbol is not allowed to explode. In addition to dot symbols, graphic elements should also try to avoid using block objects.

(5) The topographic map symbol library and line library used in each process must be consistent. The dimensions of symbol library and line library of various topographic maps must conform to the reference standards, the positioning points of point symbol library should be consistent with the acquisition points of field surveying and mapping, and the line library must be made according to the right-hand rule.

(6) In order to ensure the connectivity of the line, shielding technology is used to cover symbols, bridges, etc. , but the display order of elements should be adjusted; In particular, bridges represented by lines should be considered separately. The text is masked to 0.05 wide.

(7) using the graphic surface cleaning command to treat the suspension; The parameter is set to 0.03; Note that it is required to add the outline of the internal drawing for processing;

(8) Check the symbol mask and text mask (0. 1 mm).

(9) Data processing (map/graphic surface cleaning with Cass tool): repeated data processing (0.0 1m), hanging processing (0.0 1m), micro-short line processing (0.0 1m), etc.

(10) Drawing cleaning: clean up useless data such as abandoned layers, and check the color of layers.

2.2 Data Edge Connection, Contour Trimming and Data Checking

The edge joining method adopted by our unit is generally based on the data editor of each map and the top and left of our own map. This not only ensures that every edge is connected, but also facilitates unified management and avoids missing connections.

The outline decoration is generally in a fixed format, which only needs to be filled in according to the situation of this project, and the number of drawings and the format of the combination table need to be filled in carefully.

The most important thing after data editing is data checking. Data inspection is the most important quality control before data submission. We generally adopt the method of combining the first inspection, re-inspection and spot check. Strict data checking provides a strong guarantee for providing high-quality graphic editing results.

This paper explains the knowledge of topographic map and the important principles and methods in the process of map editing in detail. By solving the above important problems in topographic map editing, topographic map editing will become clear, and the problems in general topographic map editing will be solved.

refer to

[1] cartography [M]. Wuhan University Press.

Yang Zhonghua, Chen Lin, Yu Mingquan, et al. Modern Applied Surveying [M].Xi 'an Map Publishing House.