What are the common methods of field terrain orientation?

Here are several ways to measure the distance.

Measure the distance according to the linear ruler: when measuring the distance with the linear ruler, first measure the length between two points with two rulers (or a piece of paper, a straw, etc.). ), and keep this length, and then measured on a linear scale; Aim one end of the bipod at a whole kilometer, and put the other end on the ruler head, so that the field distance between two points can be read.

Calculate the distance according to the digital scale: according to the meaning of the scale, we can get the length of the map, the relationship between the corresponding horizontal distance of the site and the scale:

Field distance = length on the map × denominator of scale. This is our basic formula for calculating the distance. In the concrete calculation, first measure the number of centimeters between two points on the map with a ruler, and then substitute the number of centimeters into the formula to get the actual distance between the two points. If the distance between point A and point B on the map of1:50,000 is 3.4 cm, the field distance is:

3.4cm× 50000 ÷100cm =1700m

How many corrections should I add? Because of the complex terrain, it is difficult to put forward the most accurate correction number, and only a correction reference data can be provided according to the results of military experiments. This data is: when the slope is 0-5, the correction number increases by 3%; When the slope is 5- 10, the correction number is10%; When the slope is10-15, add 20%; When the slope is 15-20, add 30%; When the slope is 20-25, add 40%; When the slope is 25-30, add 50%. This is only an experimental average, some places may be larger than this number, and some places may be smaller than this number, so pay attention when using it.

(3) Topographic map 1 overview. Color of topographic map

The "guests" living on the map are actually old acquaintances we often hear and see, such as mountains, low mountains, rivers, streams, houses, highways and so on. We are all familiar with it. Why didn't you know each other as soon as you moved to the map? This is because the cartographer put on makeup and changed their faces, so it feels strange. This map has four colors, namely, black, blue, green and brown.

Residential areas, roads, independent features, boundaries, squares, place names and notes. , are highlighted, so use black;

Water is transparent blue, so rivers, lakes, reservoirs, canals, ponds and so on. They are all blue;

All kinds of plants are green. On the map, forests, nurseries, orchards and other areas are dyed light green; In the maps published after 1978, except for prominent trees and independent bushes, other vegetation symbols are printed in green.

The ground is mostly khaki, so the undulating natural form is represented by khaki-like brown on the map.

2. Names and functions of ministries outside the gallery

There are many "labels" around each contour of topographic map, which have their own names and uses. At the top and center of the map, it is called "map name and number". The picture says "Xinhua County", which is the name of the picture. This is the biggest and most famous place in this photo. "8-48-85- A", called the map number, tells you the location of this map, which is the "house number" of the map. The small print at the bottom of the map number, such as "Shangbian County, Xinhua County, Sichuan Province", indicates which counties and districts are included in this map, and whoever occupies a large area is written in the front.

There is a tic-tac-toe grid in the upper left corner of the outline, which is called a small connection graph, indicating the relationship between the surrounding "neighbors"; There is a halo line in the middle of this picture, and the names of "neighbors" are written in eight squares around it. Looking at it, you can mosaic the map.

At the bottom and center of the map is the scale, which is the standard of map size, detailed content and high precision, and also the measure of distance.

The number to the left of the scale indicates the location of the map. The line drawing is upright, with a small five-pointed star on it, indicating that it points to the North Pole of the Earth. It is called the True Sutra and the True North Line. There is a small arrow above the drawing line, indicating the direction pointed by the magnetic needle, which is called magnetic meridian, also called the magnetic north line; There is a "V" above the line drawing, which means the north indicated by the ordinate line. Together, these three directional lines are called three-north direction. Because the quality of the earth is different from place to place, these three directions are inconsistent in different places, and three angles are formed between them. The meridian shall prevail; The angle with the vertical is called the deviation angle of the coordinate vertical (also called the meridian convergence angle); The angle with magnetic meridian is called magnetic declination; The angle between the magnetic meridian and the ordinate line is called the magnetic deflection angle. According to the results of field measurement by surveyors, the directions and sizes of these three deflection angles are different in different places, so the graphics on each map are different. Subject to the true sutra: when the magnetic sutra is in the east, it is called east deviation, and the east deviation is positive. Indicated by "+",painted to the east of the True Sutra; In the west, it is called westward deviation, and westward deviation is negative. It is indicated by "-"and painted on the west side of the True Sutra. The number in the included angle is the degree of deviation from the angle, the system without brackets is 360, and the system in brackets is a dense system, which is used to correct the compass when calibrating the map orientation.

On the left side of the deflection diagram, there is a slope scale for measuring the slope. There are two lines of numbers below the horizontal line of the ruler, "1 2 4...30", which is a degree in the 360 system; "3.5, 7, 1 1 ...58%" is the degree expressed in percentage, such as 45%, which means that the horizontal distance is 100, the vertical distance is 45, and the slope is about 24. The percentage is used for engineering design.

Outside the outline on the right is a legend with common topographic symbols printed on it.

3. Description of topographic map measurement

At the right end of the bottom of the map, there is a description of map measurement and publication, telling you the method, time and basis of measurement. When using the map, you should pay special attention to:

Any words such as "aerial photography" and "surveying and mapping" indicate that this picture was measured by aerial photography and the terrain is accurate and reliable. The closer the survey date is, the more novel the map content is, otherwise the more obsolete it is.

The map is written with "1954 Beijing Coordinate System" and "1956 Huanghai elevation system", which are the basis for calculating the plane position and elevation. For example, the number of kilometers on the monument in the expressway is usually counted from the big city; How high a building is, usually from the ground. In other words, the position of any point on the earth is interrelated and has a certain relative relationship. The position of the points we draw on the ground is the same, so we should have a starting standard, otherwise we can't tell the difference between high and low. When mapping the position of a point on the ground, two starting points are needed: one is the plane position and the other is the elevation. The system for calculating these two positions is called coordinate system and height system. "Beijing Coordinate System 1954" is based on the ellipsoid of Krasovsky in the Soviet Union, which was measured in 1954, so it is called "Beijing Coordinate System 1954". The plane coordinate positions on topographic maps in China are all calculated according to this data. "956 Yellow Sea height system" was determined on 1956. According to the tidal data of the Yellow Sea at Qingdao Tidal Station 1950 ~ 1956, it is found that the height of copper wire in the tidal well of this station is 3.6 1 m, so it is determined that 3.6 1 m below the steel wire is the average sea surface of the Yellow Sea. According to this average sea level, the elevation of Qingdao leveling origin is calculated as 72.289 meters in 1956. The altitude measured in our country is calculated according to this origin.

In order to draw ground objects and landforms on the drawings, so that people who use the drawings can identify what they are, the surveying and mapping department has formulated concise symbols and relevant regulations, which are referred to as "topographic map schema" for short. The current "Schema" in China is jointly formulated by the State Bureau of Surveying and Mapping and the General Staff Bureau of Surveying and Mapping. It is the legal basis for mapping and publishing topographic maps and the basic tool for identifying and using topographic maps. With a unified schema, people who measure maps and people who use maps have a common language. When using a map, if you don't know a symbol, you can find the answer by consulting the schema. However, two points should be paid attention to when consulting the schema: first, the schema to be consulted should be consistent with the map scale used. Second, when consulting the schema, we should pay attention to the version of the schema, otherwise the symbol will be wrong.

(4) Landmark symbols

There are many kinds of objects on the ground. Due to the limitation of scale, it is impossible to draw all the objects in the picture according to their shapes. Only important features with military significance can be expressed, and some unnecessary objects have to be discarded. In order to make the map concise and beautiful, and facilitate the identification of objects, orientation determination and measurement calculation on the map, some graphs and annotations are formulated to represent some objects in the field respectively. These figures and annotations are called figure symbols.

Characteristics of 1. symbol

When formulating ground feature symbols, the following principles and features are usually considered:

First, the symbols should be unified. There is no uniform regulation, which is not only unfavorable for surveying and mapping production maps, but also unfavorable for using maps.

Second, the graphics should be eye-catching and easy to identify and remember. Symbolic graphics, as far as possible, reflect the shape and characteristics of ground objects, which users can see at a glance and easily associate with the ground objects they represent. Therefore, feature symbols strive to achieve three points in composition:

Similar to the plane shape of ground objects, such as residential areas, highways, lakes, etc. Their figures are similar to the plane outline of ground objects. This symbol is called contour symbol or orthographic symbol;

Similar to the side modeling of ground objects, such as prominent trees, chimneys, water towers and other symbols are similar to the side modeling of ground objects, which is more vivid and intuitive. This symbol is called a side symbol;

It is related to the meaning of ground objects, such as the weather vane of meteorological station and the hammer of mine. This kind of symbol is called symbolic symbol.

Knowing their characteristics, it is easy to recognize memories as long as you pay attention to the graphics and think about the meaning when using pictures.

Third, the classification of symbols should be reasonable, which can reflect the organic connection and difference of map content and ensure that the map is clear and easy to distinguish.

2. Symbol classification

It has large-scale field characteristics, such as residential areas, forests, rivers and lakes. , are drawn in proportion, this is called a symbol expressed in proportion. This symbol can be measured by its length, width and area on the map, and its distribution and shape can be understood.

For linear elements with long length and narrow width, such as roads, the Great Wall, earth dikes, fences, rivers and streams, the length is mapped according to the proportion. Because the width is too narrow, it can't be expressed when it is reduced, but it can only be enlarged, so it is called a symbol expressed in half proportion. This kind of symbol can only take its corresponding field length on the map, but not its width and area.

Small independent features on the ground, such as pavilions, detached houses, pagodas, monuments, road signs, oil wells, etc. If it is drawn on the map according to the scale, it cannot be represented; But militarily, it plays an important role in determining orientation, indicating targets, artillery joint measurement of battle formation, shooting and commanding operations. Therefore, the prescribed symbols are used and drawn on maps of different scales according to different sizes; Therefore, it is called a symbol without scale. Such symbols can not be used to judge the size of ground objects, but only to indicate the nature and accurate position of objects. They correspond to the exact position of the field, that is, the point in the diagram, which is specified according to the characteristics of the diagram.

The above three symbols can only represent the shape, position, size and type of ground objects, but not their quality, quantity and name. Therefore, there are text and numerical annotations as the supplement and explanation of symbols, so they are called annotations and explanatory symbols. There are three forms of notes and explanatory symbols:

1. Place name notes, such as the names of cities, towns, villages, mountains, rivers, lakes, reservoirs, roads and administrative districts, are expressed in different sizes.

2. Text notes describing the quality characteristics of ground features, such as the salinity of well water, the quality of highway pavement, the nature of bridges, the types of crossing fields and forests, the nature of tower buildings, etc., are attached to the side of symbols in the form of abbreviated notes.

3. Digital notes describing the quantitative characteristics of ground features, such as triangle points, mounds, heights of cliffs, forest density, average height and thickness of trees, width of roads, width, depth and velocity of rivers, are represented by numbers of different sizes.

In addition, the distribution of some features is messy, such as sand, stones, terraces, sparse forests, rows of trees, fruit trees and so on. And it is difficult to express their specific positions and quantities, so they are expressed in the form of evenly arranged patterns, so they are called configuration symbols. This symbol only indicates the distribution range, not the specific location.

As long as the characteristics of symbols are mastered, it will be easier to identify the symbols of ground objects.

(5) the expression method of landform

The surface of the earth is rugged, including mountains, deep seas, hills and plains, deserts and grasslands, rivers and lakes. How are these rugged and changeable landforms shown on the plan?

The expression method of landform is gradually improved and enriched on the basis of people's accumulated experience in practice. In more than 600 BC, cartographers in China used ∩∩ graphics to indicate the position of mountain peaks and the general trend of mountains. It was not until the early Qing Dynasty that contour lines were used to represent landforms.

Using contour lines to represent landforms can accurately reflect the height of the ground, the shape of slopes and the trend of mountains. Our basic scale topographic map mainly uses this method to represent landforms. The main problem of this method is the lack of three-dimensional sense. With the development of science, people have higher requirements for maps, hoping to see the general terrain of a vast area at a glance and quickly get the impression of elevation distribution and height difference contrast. Therefore, on the basis of contour lines, layered colors and shading methods have emerged to express landforms.

Layered coloring method is to layer the landform according to a certain height, and each layer is dyed with different colors. When you use a map, you can quickly judge the height according to your face. This method is mostly used in our common atlases, aerial maps and small-scale maps. The shading method is to draw shadows on slopes or backlit slopes with cyan (or color) according to a certain light source direction and terrain fluctuation, thus forming a three-dimensional image of terrain fluctuation, which visually gives users a vivid, winding and natural landscape feeling. This method is mostly used in landform maps and sightseeing maps.

Layered coloring and shading methods, if used with contour lines, will have better effects, which is not only convenient for identifying landforms, but also convenient for calculating elevations on maps.

1. The principle that contour lines represent landforms? To clarify this principle, let's first recall some natural phenomena.

You've been to the reservoir! On the bank slope of the reservoir, there are traces of waterline, one by one, layer by layer, winding with the convexity and concavity of the mountain, how regular! It's really like what the sculptor deliberately portrayed; In fact, it is the trace left by the impact of the water level on the bank slope during the change of the highest water level.

Look at the island again, on the steep slope around the island, like a reservoir, this is the trace left by the ebb and flow of the sea. Think about the traces of the water margin line and the principle that contour lines represent landforms, and it is easy to understand.

The principle of contour lines to represent landforms is that if a mountain crosses the mountain at the same height from bottom to top, a curved section trace will be left on the surface of the mountain, and then these section traces will be vertically projected on a plane, showing a curved figure with a circle around it. Because the height of each point on each curve is equal, this curve is called contour line; The vertical distance between two adjacent contour lines is equal, which is called vertical spacing. Topographic maps represent landforms according to this principle.

2. The characteristics of contour lines

According to the principle that contour lines represent landforms, we can see the following features from Figure 18:

Contour is a closed curve, and the elevation of any point on the same contour is equal;

If there are many contours, the mountain will be high, and if there are few contours, the mountain will be low;

Dense contour, steep slope, thin contour and slow slope; The curved shape of the contour line maintains a horizontal similar relationship with the corresponding field terrain.

For the same terrain, the number of contour lines depends on the vertical spacing. Large vertical spacing, few contour lines and simple landform display; The vertical interval is small, the contour lines are dense, and the landform is displayed in detail. In order to facilitate and use the map, we should choose an appropriate vertical interval. The vertical spacing of our basic scale topographic map is stipulated as follows:

Proportion1:1:250001:500001:65438+1:200000.

The vertical spacing is 2.5m10m 20m40m.

3. Types of contour lines

On the topographic map, why are the contours we see thin, thick and intermittent? This is stipulated to better represent the terrain and facilitate the use of maps.

The contour lines that are surveyed at vertical intervals according to regulations are called basic contour lines, also known as the first curve, and are represented by thin solid lines;

In order to calculate the elevation conveniently, drawing the first curve every five or ten lines is called bold contour line. For example, a mountain with a height of 1000 meters will draw 100 first curves on the map of 1:50000. It is not convenient to calculate the elevation one by one. With the bold outline, detailed statistics can be made and calculation is convenient. Therefore, it is also called a curvometer.

Because the landform is changeable, it is often impossible to express the detailed features of the landform with the first curve, so a long dotted line is drawn in the middle of the first curve to express its details, which is called the half distance (half of the basic vertical interval) contour line, also called the middle curve.

In some places, when the interval curve is still not displayed, the short dashed line is used to represent the fine appearance of the quarter position of the vertical interval, which makes up for the deficiency of the interval curve, so it is called supplementary contour line, also called auxiliary curve. ~

Interpolation curves and auxiliary curves, with short line segments, are only used for oblique transformation and places with complex terrain, such as maps in hilly areas.

It is a scientific method to represent landforms with contour lines, which has the advantages of simple graphics, easy calculation, clarity and eye-catching. However, there are also some shortcomings. For example, because contour lines are drawn at certain vertical intervals, some fine features may be missed. Can not fully reflect the details and landscape of the landform; The three-dimensional sense is not obvious enough, which brings certain difficulty to the deduction. When using a map, we should not only master its characteristics, but also know its shortcomings, so as to better play the role of topographic maps.

4. How to identify landforms

We understand the principle and characteristics of contour lines representing land, and we have the basis to explain landforms. However, due to the complexity of landform types, there are still many difficulties in correctly understanding landforms.

Although each mountain has its own characteristics and different shapes, as long as it is carefully analyzed, it can still find out their common characteristics. Generally speaking, they are all composed of mountain tops, depressions, mountain backs, valleys, saddles and ridges. As long as these basic features are mastered, it is easier to identify landforms.

When recognizing these features, as long as we think of the principle and characteristics of contour lines representing landforms, we can immediately recognize that all the smallest closed circles are mountain tops. According to the size and shape of these circles, we can also judge whether it is spire mountain, dome mountain or Pingdingshan. Hollow is also a small circle. How can it be different from the top of the mountain? Cartographers have long thought of this problem, that is, adding a short vertical line to the circle to indicate the downward direction, which is called the slope line. If you see the slope line outside the circle, it is the top of the mountain, and the slope line is inside the circle, it is concave.

Taking the top of the mountain as the base point, the contour line protrudes outward from the back of the mountain; A valley is a place where the contour line sinks inward. Between the two hills, there are two groups of contour lines that are convex and relatively curved with the saddle, and several convex parts connecting the hills and the saddle are ridges.

In addition, due to the uplift, denudation and accumulation of the earth's crust, some local areas have changed their original appearance, such as the Loess Plateau, where vegetation is scarce and rain erosion forms gullies; The cliff is steep, with a slope of more than 70, like the steep stone mountain in Guilin, Guangxi; Cliff collapse, etc. Caused by weathering on the hillside. These landforms are collectively called deformation sites in the military. Because of its small area and peculiar shape, this terrain is not easy to be represented by contour lines, so it has to be represented by symbols.

According to the principle and characteristics of contour lines to express landforms, combined with deformation symbols, and taking into account natural habits (such as rivers always flow downwards, the prefix of elevation notes on contour lines always faces uphill, and the slope line points downhill), the whole and details of landforms will be clear.

5. How to judge altitude and height difference?

When we use a map, we often need to determine the elevation of a point. Such as artillery shooting, in order to determine the high and low angles, it is necessary to know the heights of artillery positions, shooting targets and observation posts. What is the basis for judging the elevation of a point on the map? Mainly based on elevation notes and contour lines. For example:

When the point is just on the contour line, the elevation of the contour line is the elevation of the point;

When the point is between two contour lines, the elevation of the next contour line is calculated first, and then the height is estimated according to the position of the point in the interval between the two contour lines;

When the point is at the top of the mountain and there is no elevation note, generally, the elevation of the top contour line should be determined first, and then half a vertical interval should be added.

Know the elevation of two points, and then subtract them, and the result is the elevation difference of two points.

6. How to judge the shape and inclination of the inclined plane?

When building a hill position, troops should always observe the slope to see if it is conducive to the development of firepower. When troops March, they often encounter uphill and downhill. Different slopes and slopes have different effects on military operations. For example, the climbing ability of a car is 15. If the longitudinal slope of the road is greater than 15, cars are inconvenient to pass. So when we use the map, we should learn to judge the shape and slope of the slope from the map.

The so-called inclined plane is the inclined part from the top of the mountain to the bottom of the mountain. Take the highlands controlled by opposing sides as an example. The slope facing the other side is called the positive slope, and the slope facing away from the other side is called the reverse slope. How many kinds of inclined planes are there? How are they represented on the topographic map?

The gradient of homogeneous slope is basically the same. Standing on the top of the slope, you can take in everything in a glance, which is convenient for carrying firepower forward. On the map, the intervals of contour lines are roughly equal. vJl4.nk

The convex inclined plane is on the ground, which is gentle on the top and steep on the bottom. Standing on the top of the inclined plane, it can't see the bottom, forming a dead angle for observation and shooting, which is called the convex inclined plane. On the diagram, the interval of contour lines is fine on the top and dense on the bottom.

The concave inclined plane is opposite to the convex inclined plane, steep on the top and gentle on the bottom. Standing on the top of the inclined plane, you can see the whole picture of the inclined plane, which is convenient for developing firepower. It's called a concave slope. On the map, the interval of contour lines is dense on the top and thin on the bottom.

Most of the slopes on the ground are uneven, but they are always inseparable from the three shapes mentioned above. When using a map, you can easily identify the shape of the slope as long as you pay attention to the density of contour intervals.

So how to measure the slope of the inclined plane from the map? .

When measuring the slope, we should first measure the width between two (or six) contour lines on the map with two rulers, then measure it on the slope scale, and then read the slope at the bottom of the corresponding vertical line.

(6) topographic map coordinate system

The word "coordinate" may be a little strange to some readers, but it is often encountered in our lives, just not called that. For example, we go to the stadium to watch the ball game and listen to the report in the auditorium. There is a number on the admission ticket. According to this number, we can find our seats. This method of determining seats by row number and number is mathematically called coordinate method. In order to facilitate the use of the map, the cartographer moved this coordinate method to the map and became a method to determine the ground points. Because the earth is relatively large, there must be a series of regulations on the starting point, calculation method and expression of coordinates. These rules are coordinate systems.

There are two kinds of coordinate systems on the map, the plane rectangular coordinate system and the geographical coordinate system. The topographic map of our country adopts "Beijing coordinate system of 1954", which we have already introduced. Here I only intend to introduce some specific applications of geographical coordinates and plane rectangular coordinates in topographic maps.

1. Geographical coordinates

Determining the latitude and longitude of a point on the earth's surface is the geographical coordinates of that point.

For convenience of use, the longitude and latitude lines are drawn at regular intervals on1:200,000,1:500,000,1:kloc-0/000,000 map to form a geographical coordinate network; The outline of the map is marked with numbers of latitude and longitude. On the map larger than 65,438+0: 65,438+million, only the graduation zone is drawn outside the inner contour, and each graduation is divided into a point; Warp yarns, weft yarns and values are marked on the four corners of the inner contour. When the target needs to be expressed by latitude and longitude, as long as the south map and the north map, the east map and the west map are connected by corresponding divisions, a geographical coordinate map is formed.

Ridge coordinates are common all over the world. In maritime, air, frontier defense or diplomatic struggles, geographical coordinates are usually used to represent targets. For example, if we know that the geographical coordinates are 25 02.5' north latitude and12131'east longitude, we can find that this is Taipei. On the other hand, if we find the location on the map, we can also find the geographical coordinates of this point. ：

2. Plane rectangular coordinates

Because the longitude and latitude lines are mostly arcs on the map, it is not convenient to operate on the map, and it is not convenient to convert the distance and angle. Therefore, draw a plane rectangular coordinate network on a large-scale map.

Determine the length of a point on the plane, which is the plane rectangular coordinates of the point. The values of plane rectangular coordinates are expressed in kilometers and meters.

Plane rectangular coordinates constitute plane rectangular coordinates, which is a coordinate system established by two vertically intersecting lines on the cheek. The vertical line is the vertical axis, represented by X; The horizontal line is the horizontal axis, represented by y; The intersection of two straight lines is the coordinate origin, which is represented by 0. When determining the position of a point, the vertical distance from the point to the horizontal axis is taken as the ordinate (X) and the vertical distance to the vertical axis as the abscissa (Y). It is also stipulated that the value of x above the horizontal axis is positive and the value below it is negative; The y value is positive on the right side of the vertical axis and negative on the left side. For example, the coordinates of point A: X=250, Y=300. Determining points in this way is called plane rectangular coordinate method.

On the topographic map of our country, the plane right-angle network is formed according to Gaussian projection. Gaussian projection takes 6 as a strip, the central meridian of each projection strip is a straight line, and the other straight line perpendicular to the central meridian is the equator. The plane rectangular coordinates on the topographic map take the central meridian as the vertical axis (X), the equator as the horizontal axis (Y), and their intersection point is the coordinate origin (0). In this way, each projection area constitutes an independent coordinate system. Our territory is located in the north of the equator, so the ordinate (x) values are all positive; The value of the abscissa (y) is positive to the east of the central meridian and negative to the west of the central meridian. To facilitate the calculation and elimination of negative numbers, the abscissa (y) plus a constant of 500 kilometers (that is, the longitudinal axis moves 500 kilometers to the west), and the value of y is positive.

Because a projection area has a large range and many sub-images, in order to quickly determine the coordinates of points, parallel lines are used to form square grids in units of one kilometer (or two kilometers), which are called plane rectangular coordinate grids. On the topographic map of1:50,000, the area of each grid is one square kilometer, so it is also called square grid.

The vertical lines on the map (that is, the parallel lines of the central meridian) are called ordinate lines, and their length values increase from south to north, and the notes are between the left and right profiles (kilometers). The horizontal lines on the map (that is, lines parallel to the equator) are all called abscissa lines, and their length values increase from west to east. Pay attention to the distance (kilometers) between the upper and lower corridors.

Using plane rectangular coordinates to indicate that the target has a set of x and y values, can you determine the position of any point on the earth's surface on the map? This is possible in the projection area. However, according to the method of Gaussian partition projection, the world is divided into 60 regions, and we in China account for 13 regions, each of which is an independent coordinate system; In this way, the same coordinate values will appear in all sixty bands at the same time. For example, the coordinates of Hohhot and Chengde are almost equal, but the actual distance between the two places is nearly 500 kilometers, just because the projection zones are different. In order to avoid this phenomenon, it is necessary to write a number before the Y coordinate value, that is, 19 before the Hohhot abscissa value and 20 before the Chengde abscissa value, so that the position of any point on the earth's surface can be determined by the X and Y values.

The function of plane rectangular coordinate network is mainly to indicate the target and determine the position of the target on the map, and also to estimate the distance and area. When using coordinates to indicate a target, you can use rough coordinates or precise coordinates. For example, to report the approximate coordinates of Kameyama, just point out the coordinate values in the lower left corner of the square where Kameyama is located.

The order of submitting coordinates is: ordinate value first, then abscissa value, remember not to report errors.

In order to avoid the wrong order, a simple method is to align the left corner of this square with the tiger's mouth of the left hand. First, find out that the ordinate value (X) is 85 along the thumb direction, and then find out that the abscissa value (Y) is 49 along the index finger direction. When giving an oral report, say the coordinates first, and then the place name, such as 85, 49, Guishan. If it is in the file, it will be written as "Kameyama (85, 49)".

When artillery fires, it is often necessary to use accurate coordinates. At this time, we must first find out the approximate coordinates, plus the meters of the vertical distance between the point and the lower and left grid lines. The most convenient method is to read with a coordinate ruler. The method of measuring reading is: make the vertical edge of the coordinate ruler close to the vertical coordinate line, and the horizontal edge pass through the positioning point of the measured object, so that the meters of the vertical and horizontal coordinates can be read, and the kilometers of the coarse coordinates are added, which is the accurate coordinates. For example, the exact coordinates of the launch point are: X85620, Y49300.

On the other hand, the position of the target point on the map can also be determined by knowing the coordinate values, which will not be introduced in detail here.

3. Adjacent complementary coordinate network

The plane rectangular coordinate network on topographic map is an independent coordinate system established according to the projection zone, and the vertical and horizontal lines are only parallel to the vertical and horizontal coordinate axes of the zone; Therefore, where two belts meet, the coordinate lines on the map cannot be spliced. However, in actual combat, this situation is often encountered: than

In order to facilitate the use of a unified coordinate network for the maps of two adjacent belts, it is stipulated that the short line of the coordinate network of two adjacent belts should be drawn on the outer contour line of the map at the intersection of two belts 1 ~ 2, and the corresponding kilometers should be marked. When using a map, it is necessary to use a coordinate network uniformly, and connect the short lines between two corresponding galleries into a straight line, which can form a unified coordinate network of adjacent areas.

Q:

Observing such a topographic map, we should pay attention to those places, such as the woodland of every household is not on the obvious ditch beam, but between them. How should this land be drawn on the topographic map? Because the area of each household is calculated from the topographic map by grid paper, drawing is very important. Please pay more attention, thank you!