Map sheet numbering refers to the practice of dividing the map sheets within the scope of a certain scale map into many maps according to a certain size and numbering them. There are two ways to divide a map: trapezoidal division and rectangular division.

Trapezoid framing

Trapezoid division is a division method in which a map sheet is divided by a trapezoid with a certain longitude and latitude difference, and each map outline is formed by longitude and latitude lines. Trapezoidal framing is used for topographic maps on scales from 1: 5,000 to 1: 1,000,000. Division by longitude and latitude, also known as international division, is applicable to the division of medium and small scale topographic maps. The Basic Scale topographic map in China is based on the international unified division of 1: 1,000,000 scale topographic map. According to a certain longitude and latitude difference, the Map Range is divided step by step from 1: 1,000,000 to 1: 5,000, so that the number of adjacent scale topographic maps is a simple multiple relationship.

Advantages of trapezoidal framing:

• The system is strong, and the latitude and longitude difference ranges contained in various scale maps have a certain multiple relationship;
• Each map sheet has a clear concept of geographical location, which is applicable to the map sheets of the whole country, continents and the whole world;
• Each map can be measured and drawn at the same time, and there will be no repeated leakage.

Disadvantages of trapezoidal framing:

• When the longitude and latitude lines are projected on the city curve, it is not convenient to splice;
• With the increase of latitude, the area limited by the same difference between longitude and latitude is shrinking, which makes the size of the map different, and is not conducive to the effective use of paper and printing machine layout, but this problem can be solved by the way of combining;
• The integrity of important geographical targets may be destroyed when they are divided according to certain longitude and latitude differences.

Rectangular framing

Rectangular division refers to the division of map sheets according to rectangles of a certain size, so that each map has a rectangular outline, and its adjacent map sheets are divided by straight lines. Rectangular division is used for 1: 500-1: 5000 maps. The map is divided according to the coordinate grid. The map is rectangular or square. It is suitable for large-scale maps.

Advantages of Rectangular Framing:

• The establishment of a cartographic network is very convenient;
• The drawings and attachments are closely combined, and the outline of the drawing is the coordinate grid line, which is convenient for splicing and application;
• The printing area of each drawing is relatively balanced, which is conducive to making full use of paper and printing machine layout;
• Makes it possible to consciously avoid important figures in order to keep their figures intact on the map surface; frame lines.
• The size of the drawing is the same, which is convenient for storage and use.

Disadvantages of rectangular framing:

• There is no clear GCS in the map profile, which makes the map sheet lack of accurate geographical concept;
• The mapping area can only be projected once, and the deformation is large.

Executive summary:

Trapezoid framing and numbering

Rectangular tiling and numbering