What are Topo Maps?

The topographic map refers to the projected view of the undulating shape and geographical position and shape of the ground surface on the horizontal plane. Specifically, the ground features and landforms on the ground are projected horizontally (projected along the direction of the plumb line to the horizontal plane) and reduced to a certain scale on a drawing. This kind of map is called a topographic map.

People see the topographic maps that reflect the shape and appearance of the earth's surface. Whether it is a mountainous area with undulating terrain, or a water town plain with dense rivers and ponds, the various landforms and features on the map accurately reflect the actual situation on the ground. How are they mapped?

This must first clearly determine the three basic elements required for each point on the topographic map: bearing, distance and elevation. At the same time, these three basic elements must also be based on the starting direction, coordinate origin and elevation zero.

When using a piece of white paper fixed on the chart to map the topographic map, you must first orient the chart. This can be based on the measured in advance.

Maps have been used by humans for a long time. But maps were not printed as documents until modern times. Maps draw roads, settlements, natural features, etc. on paper or other materials such as sheepskin-so you get a floor plan that describes the real world. along with

Geological map framing method: Trapezoidal framing method based on longitude and latitude lines is generally used for 1: 5000-1: 1 million medium and small scale map framing; rectangular framing method based on coordinate grid framing, generally Used for urban and engineering construction of large scale maps from 1: 500 to 1: 2000.

1. Trapezoidal framing and numbering of topographic maps

The trapezoidal framing of the map is also called international framing, and is divided by the longitude and latitude lines stipulated by the international uniformity. As the meridian converges towards the north and south poles, the entire map is trapezoidal. The division method and number vary with different scales.

Topographic map of arctic region

1) 1: Fraction and numbering of 1 million topographic maps

The standard scale of international 1: 1 million maps is 6 ° longitude and 4 ° latitude. As the area of the map shrinks rapidly as the latitude increases, it is stipulated that two frames are merged between 60 ° and 76 ° latitude, that is, each map includes The longitude difference is 12 °, and the latitude difference is 4 °. The four images are merged between latitude 76 ° and 88 °, that is, each picture includes longitude difference 24 °, latitude difference 4 °; a latitude above 88 ° is a pair.

1: The scale of the 1 million topographic map is from the earth's equator (latitude 0 °) to the north and south poles, and every horizontal latitude difference 4 ° is a horizontal line, which is represented by the letters A, B, C, D, ..., V in that order ; Starting from longitude 180 °, every 6 ° from west to east is a column, which is represented by numbers 1, 2, 3, ..., 60 in that order. Figure 10-1 shows the international scale and number of the map of 1: 1 million north latitude in the eastern hemisphere. For each picture number, first write the horizontal code, draw a horizontal line in the middle, and then write the vertical code. For example, somewhere in Beijing, the latitude is 39 ° 56 'north latitude and the longitude is 116 ° 22' east longitude. The scale of the 1: 1 million scale map at this point is J-50.

2) Fragmentation and numbering of 1: 500,000, 1: 250,000, and 1: 100,000 maps

The division and numbering of these three scale topographic maps are based on the division and numbering of the map with a scale of 1: 1 million, according to the corresponding latitude and longitude differences in Table 10-1. ^[3]