# Division and Numbering of Topographic Maps

The national basic scale topographic maps are 1:100, 1:25,000, 1:50,000, 1:100, 1:200, 1:500, and 1:10 million. Ordinary maps are usually divided into large, medium and small scales. Generally, maps with a scale of 1:100,000 and larger scales are called large scale maps; 1:100,000 to 1:100 million are called medium scale maps; less than 1 : 1 million is called a small scale map. For a country or a world, the framing number is especially necessary when measuring the various scale topographic maps. Usually this is a unified frame framing and numbering system developed by the national authorities。

## Fragmentation of topographic maps

At present, the scheme of topographic map segmentation in China is based on 1:1 million topographic maps and defines larger scale topographic map segmentation according to the same longitude and latitude differences. A map of one millionth of a map between latitudes 0o - 60: sup: o the size of the frame is by the difference of 6:sup:o Latitude difference 4o Fragmentation; the frame between 60o-76:sup:ohas a difference of 12o, weft The difference is 4o; the difference between the frames in 76o-80:sup:ois 24o, latitude difference It is 4o, so each one-millionth map is slanted by 6oand latitude 4o

Each large-scale topographic map within one millionth of each level is divided according to the corresponding latitude and longitude differences. Among them, 1:500,000, 1:200,000 and 1:100,000 scale topographic maps are directly divided on the basis of one millionth of the map. One millionth topographic map is divided into four 1:500,000 topographic maps, each with a longitude difference of 3.o Latitude difference 2o A one-millionth map is divided into 36 topographic maps of 1:200,000, each with a longitude difference of 1.o A map of one millionth is divided into 144 topographic maps of 1:100,000, each with a latitude difference of 30’, and latitude difference of 20’。

Each topographic map larger than 1:100,000 scale is divided step by step on the basis of 1:100,000 map, one 1:100,000 topographic map is divided into four 1:50,000 topographic maps, and one 1:50,000 topographic map is divided into four 1:25,000 topographic maps. On the basis of 1:100,000 map, 64 1:10,000 topographic maps are divided, and one 1:10,000 topographic map is divided into 4 1:5,000 topographic maps (see Table 4-1)。

Table 4-1: The size of basic scale topographic maps and the quantitative relationship between maps。

 比例尺（万） 图幅大小 图幅间的数量关系 经度 纬度 1：300.8 6度 4度 1 1：295.0 3度 2度 4 1 1：295.0 1度 40分 36 9 1 1910 30分 20分 144 36 4 1 1：295.0 15分 10分 576 144 1967 4 1 1：293.5 7.5分 5分 2304 576 64 1967 4 1 1:1 3分45秒 2.5分 9216 2304 256 64 1967 4

## Split number

The numbering of topographic maps is to give a fixed number to each map according to the division of topographic maps of various scales. This number can not be repeated, and it should be kept systematic。

The most basic method of topographic map numbering is to use the determinant method, that is, to make a number of rows and columns in a certain range of each map。

### Number of 1：1 million maps

This kind of topographic map is numbered as a global uniform block number。

Number of columns: from equator to North and south poles with latitude difference of 4o For a row, up to 88 north and 88 southo (North-South latitude 88)o To the North and South Poles, polar projection is used to map the two hemispheres separately. The two hemispheres are divided into 22 columns, using the Latin letters A, B, C and D, respectively. V says。

Number of rows: from longitude 180 o From east to east every six o For a row, there are 60 rows around the earth, with numbers 1, 2, 3, 4… 60 indicates。

Since the longitude of the two hemispheres is the same, it is stipulated to add an S before the map number of the southern hemisphere and no sign before the map number of the northern hemisphere. Generally speaking, the letters of column number are written in front, the numbers of rows are written in back, and the middle is connected by a short line. For example, one millionth of Beijing’s map is numbered J-50 (as shown in Figure 14)。

Since the earth’s meridian converges to the poles, as the latitude increases, the same 6o is poor, but its latitude arc length has gradually narrowed, so it is specified at latitude 6060:sup:o-76 The frame between ois double-merged (the difference is 12:sup:o, the latitude is 4:sup:o); at latitude 76o The frame between -88:sup:ouses four merges (the difference is 24oand the latitude is 4o). The number of these merged frames, the number of columns is unchanged, and the number of rows (whether containing two or four) is written side by side. For example, north latitude 80o-84:sup:o, west longitude 48o-72:sup:ois a one-millionth map number It should be U-19, 20, 21, 22 (Figure 4-14)。

1 million topographic maps (Northern Hemisphere)

### 1:500,000, 1:200,000, 1:100,000 topographic map number

A 1:1 million map is divided into four 1:5 million maps, which are represented by A, B, C and D respectively. The number is added to the number of the 1:1 million topographic map with its own serial number, such as J-50-B。

A 1:1 million map and36 maps of 1:2 million maps, which are represented by bracketed numbers (1) - (36) respectively. The number of a 1:1 million topographic map is followed by its own serial number, such as J-50-(28)。

A 1:1 million map is divided into 144 1:100,000 maps, which are represented by numbers 1-144. The number of the 1:1 million topographic map is added with its own serial number, such as J-50-32. (Fig. 4-15)

1:500,000, 1:200,000 and 1:100,000 topographic maps

### 1:50,000, 1:25,000, 1:10,000 topographic map number

Based on the numbering of 1:100,000 topographic map, a 1:100,000 map is divided into four 1:50,000 maps, which are represented by A, B, C and D respectively. The numbering of the 1:100,000 topographic map is followed by its own serial number, such as J-50-32-A. Another 1:50,000 map is divided into four 1:25,000 topographic maps, which are represented by 1, 2, 3 and 4. The number of the map is added to the number of the 1:50,000 topographic map, such as J-50-32-A-1。

The number of 1:100000 topographic map is divided into 64 1:100000 topographic maps with brackets (1)-(64). The numbering of 1:100000 topographic map is followed by the numbering of 1:100000 topographic map, such as J-50-32-(10)。

A 1:10000 topographic map is divided into four 1:5000 topographic maps, which are represented by the lowercase Latin letters a, b, C and D. Its number is added after the 1:10000 map number, such as J-50-32-(10) -a。