High-quality courses-engineering measurement-Chapter 1-Introduction

Content:Master the basic concepts, tasks, and functions of engineering measurement, and understand the geoid, geoid, and geographic coordinate system (Earth and astronomy) concepts of independent plane Cartesian coordinate system, Gaussian plane Cartesian coordinate system, absolute elevation, relative elevation and height difference; understanding the limits of water plane replacing level, organization principles of measurement work andProgramAnd the learning methods of this course.

Important:Measure the similarities and differences between the Cartesian coordinate system of the upper plane and the Cartesian coordinate system of the cartesian plane in mathematics; the principles and procedures of the measurement work.

Difficulties:Concept of the Cartesian coordinate system of the Earth level and Gaussian plane; Method for Determining the point on the ground.

§ 1.1 development, learning significance and requirements of Surveying

I. development overview of Surveying

1. Achievements of Ancient Chinese Surveying

China is an ancient civilization in the world. Due to the needs of life and production, the measurement work started very early and has made brilliant achievements in measurement. The following examples are provided.

(1) map of the Changsha state Unearthed from tomb 3 of mawangdui, Changsha-the world's earliest military map.

Note: The oldest map in the world is the one found on the pottery sheet in the city of gasuguba (today in Iraq) in the northern part of the ancient Babylon. The pictures show the ancient city of Babylon, the river tiriss, And the ayurathati River. It was engraved in 2500 BC and has been around four thousand years ago.

(2) the discovery of magnetic slip angle is recorded in Mengxi pen talk, Shen Kuo in the Northern Song Dynasty.

(3) in the Qing Dynasty, Emperor Kangxi completed one of the world's earliest topographic maps in 1718.

Under the auspices of the three Emperors of the Qing Dynasty: Kang, XI and Qian, from Kangxi to Qianlong for 25 years, that is, from 1708 to 1760, china's land survey has made brilliant achievements. It is also the first Chinese-foreign people to cooperate in the history of world surveying and mapping to draw national maps, provincial maps, and specialized maps, over one thousand square kilometers in mainland China, the grand performance of large-scale triangle measurement has been completed.

2. Current Development Status and Prospects of Surveying

(1) Integration of indoor and outdoor measurement of total stations.

(2) The development of GPS (global positioning system.

(3) the development of remote sensing RS (remote sense.

(4) the development of geographic information system (GIS.

(5) The combination of 3 S technology and the concept of Digital Earth.

3,Significance and requirements of this course

The significance of this course:

(1) The design, construction, completion, expansion and maintenance, and deformation monitoring of civil engineering (including highway, construction, and municipal administration) should be measured.

(2) Learn measurement well from the characteristics of higher vocational majors. Higher vocational education is to train high-level specialized application talents. Higher Vocational majors pay more attention to the cultivation of hands-on abilities, and measurement courses are one of the important ways to cultivate hands-on abilities.

Master the requirements of this course:

Take lectures seriously, take notes, complete homework independently, and take lab courses seriously.

4. Classification of measurement disciplines

Definition of measurement:

Surveying is a science that studies the shape and size of the earth and determines the ground (including air, underground, and submarine) points. Based on its tasks and functions, there are two parts:

Measurement (ing)-from ground to graphics. Refers to the use of measuring instruments, through measurement and calculation, to obtain a series of measurement data, or the terrain of the earth's surface is reduced to a topographic map.

Test setting (Lofting)-from the image to the ground. It refers to the calibration of the planned locations of buildings and structures on the ground as the basis for construction.

Classification of measurement disciplines:

The measurement discipline produces many branch sciences based on different research scopes and objects. Generally divided into: general surveying, geosurveying, photography, engineering surveying and cartography.

Engineering Measurement refers to the survey and design, construction, completion, deformation observation and operation management of engineering construction and resource development.

§ 1.2 Determination of ground points

The determination of the ground point usually requires three quantities. In the measurement work, we usually use the projection position (x, y) of a certain point on the datum plane and the height (H) of the point from the datum plane to determine.

I,Measurement Datum

1. Measurement Work datum-level and geolevel.

Measurement is performed on the Earth's surface, and the ocean accounts for 71% of the earth's surface, so the earth's surface is most representative of the sea surface, people regard the Earth shape surrounded by sea water as the shape of the earth. Select the sea surface for measuring the working datum.

Level-a closed surface formed by a static sea surface.

Geolevel-the level through which the average sea surface is used.

Characteristics of the leveling surface-a gravity equality surface that is orthogonal and closed to the vertical line everywhere.

Vertical Line-the baseline for measurement.

Level and OID

2. measurement and calculation datum-rotating elliptical

Due to the uneven distribution of mass inside the Earth, irregular changes may occur in the direction of the vertical line. As a result, the geoid becomes a complex surface and cannot process the measurement data on this surface. For the convenience of calculation, A ry which is very close to the OID and can be expressed in mathematical form instead of the Earth shape is usually used, which produces the concept of "Rotating elliptical.

Elliptical rotation: an elliptical body that is rotated by an elliptic (long half-axis A, short half-axis B) around its short half-axis B.

2. Coordinates of ground points

Coordinates are divided into geographical coordinates, Gaussian plane Cartesian coordinates, and plane Cartesian coordinates.

1. geographic coordinates (belonging to the Spherical Coordinate System)-expressed by longitude and latitude.

Applicable to: determining points on the Earth's elliptical sphere.

2. Cartesian coordinates of the plane, which are expressed by coordinates (x, y.

Suitable for: The measurement area has a small range, and the measurement area surface can be viewed as a plane.

Compared with the Cartesian coordinate system in mathematics,Differences:

(1) take the north-south direction as the vertical axis (X axis) and the East-West direction as the horizontal axis (Y axis)

(2) clockwise angle measurement, clockwise quadrant number.

Similarities:The Triangle Formula in mathematics can be directly applied in measurement calculation.

Measuring the Cartesian coordinate of a plane in Mathematics

3. Cartesian coordinates of Gaussian plane

Applicable to: The measurement area has a large scope and cannot be regarded as a plane.

When the measurement area is large and the surface is treated as a plane, the image on the Earth's elliptical sphere is painted to the plane, which will inevitably produce deformation. To reduce the deformation, an appropriate solution is required. The common measurement method is Gaussian projection.

The Gaussian projection method divides the earth into several bands and then projects each band onto a plane.

(1) Division of the 6° band

1) to limit the longer the Gaussian projection distance from the central meridian, the longer the length deformation is, divide the whole earth into 60 bands starting from 0 ° longitude and 6 ° into one band.

2) formula:

-- Central meridian longitude; n -- the belt number of the projection band.

(2) Division of 3 ° band

Starting from the eastern longitude, the whole earth is divided into 120 belts, with a 3 ° belt.

Include:

-- Central meridian longitude; n -- the belt number of the projection band.

4. Representation of Cartesian coordinates of Gaussian plane in China.

Method: (1) Add the x-axis Y of the natural value to 500000 meters;

(2) mark the new X-axis Y with a 2-digit number.

[Example]:Point P (3032586.48, 20648680.54) of the National Gaussian plane. What is the belt number and the natural coordinate?

(1) Distance from point P to the Equator: x = 3032586.48 m

(2) The actual distance from the X axis of the Y axis of the projection belt to the Y axis of the Y axis is 648680.54-500000 = 148680.54 M.

3. elevation of ground points

1. Absolute Elevation H (altitude)-vertical distance between the ground point and the Earth level.
2. relative elevation H'-the vertical distance between the ground point and the assumed level.
3. High Deviation -- H AB = h B-H a = H 'B-H'

V. Elevation System in China

Mainly include:

(1) China National Elevation System (1985)

(2) 1956 Yellow Sea Elevation System

(3) Local Elevation System. For example, the Pearl River Elevation System.

Among them, China's level origin is built in Qingdao Guanxiang mountain, in 1985, the National elevation system, its elevation is 72.260 meters, in 1956 the Yellow Sea Elevation System elevation is 72.289 meters.

§ 1.3 Overview of measurement work

I,Basic work of measurement

Because the relationship between the ground points is determined by the horizontal angle (direction), distance and height difference, angle measurement, distance measurement, and elevation measurement are the basic tasks of measurement, observation, computation, and plotting are the basic skills in measurement.

II,Limit for replacing the level with a horizontal plane in Measurement

The water plane instead of the level can greatly reduce the measurement and drawing operations. The following describes the effects caused by this.

1. The influence on the horizontal angle and distance is negligible within an area of about 320 square km.

2. The influence on the elevation-even if the distance is short, the influence of the curvature of the Earth must be taken into account.

III,Basic Principles of measurement

1. The layout is "from whole to local", the precision is "from advanced to low", and the work order is "first controlled and then detailed ".

2. Another principle. That is, "the previous step is not checked and no further work is performed ".