What is elevation measurement?

Question1:What is the elevation of 5 minutes? Elevation refers to the distance from a point to the absolute datum along the vertical line, which is called absolute elevation. It's short for elevation The distance from a point along the vertical line to an assumed horizontal base surface is called assumed elevation.

"Elevation" is a surveying and mapping term. Popular understanding, altitude is actually altitude. In surveying, the definition of elevation is the height of a surface point in the direction of gravity, that is, the height of the gravity line where the center of gravity is located. So the elevation direction of every point on the earth's surface is different.

"Elevation" is the element that determines the location of ground points. The methods of elevation measurement include leveling and trigonometric leveling, and leveling is the main method of accurate elevation measurement. Leveling is a method to measure the height difference between ground points and calculate the elevation by using an instrument (level) that can provide horizontal line of sight.

There are mainly two kinds of altitude systems adopted by countries all over the world: positive altitude system and normal altitude system, and their corresponding elevation names are high altitude and approximate altitude respectively, which are collectively called elevation. The normal height system and the positive height system are blessed, mainly because the gravity field has different effects, and the gravity line will produce some deviations. The height system adopted in China is normal. If it is not for scientific research, but for general use, the result of normal altitude system can also be called altitude in China.

In the past, China used the mean sea surface of the Yellow Sea obtained from the observation results of Qingdao Tidal Observatory 1950- 1956 as the elevation zero point, which was called "Yellow Sea 1956 height system". After reexamination, it was found that the tidal data in height system was too short and the accuracy was poor, so it was recalculated with the observation data of Qingdao Tidal Station 1950- 1979 and named as "National Elevation Datum 1985". The national leveling point is located in Guanxiangshan, Qingdao, as the basis of elevation measurement in China. Its elevation is calculated with the average sea level set by "National Elevation Datum 1985" as zero point, and the original elevation of "Yellow Sea height system 1956" is abolished.

The attached picture shows Mount Everest. In 2005, China re-measured the elevation of Mount Everest, which was the largest elevation measurement in history. The investigation cost a lot of money and took nearly half a year. After the survey, the survey results were released in September 2005: Everest is 8844.43 meters above sea level. On October 9th, 65438/KLOC-0, the State Bureau of Surveying and Mapping officially announced that the new height of Mount Everest was 8844.43 meters. I used 8848. 13m for many years before, but I don't need it anymore.

There are two main methods to measure the height of Mount Everest: the first method is the traditional classical measurement method, that is, based on triangulation, leveling, triangulation, traverse survey and other methods to correct the data of gravity, atmosphere and so on, and finally get the effective data of Mount Everest elevation. The second method is GPS satellite geodesy. Firstly, a reference ellipsoid that can fit the shape of the earth to the greatest extent is established, and the accurate three-dimensional coordinates of Mount Everest relative to this earth reference ellipsoid are obtained by satellite GPS instruments. Then, as long as the height difference between the reference ellipsoid of the highest point of Mount Everest and the real earth is determined, the accurate elevation of Mount Everest can be obtained.

Question 2: What is the method of elevation measurement? The elevation measurement method comprises the following steps:

(Premise: there are known joint survey elevation points)

1. Calculate the height difference between the known point and the fixed point by leveling, plus the elevation of the known point. -Leveling is divided into first-class to fourth-class and super-class;

2. Solve the problem by trigonometric leveling, that is, measure the slope angle and oblique distance between the known point and the to-be-fixed point, and then calculate the height difference by trigonometric function, plus the elevation of the known point-at present, rangefinder and total station are very common, and trigonometric leveling is very convenient, so trigonometric leveling can be replaced by trigonometric leveling when the accuracy requirement is not too high.

3. Measuring elevation with barometer is the simplest method, but it is also the method with the lowest accuracy.

4, high-precision GPS joint measurement, plane coordinates and elevation observation and touch at the same time, the accuracy is also good.

Question 3: What is the conversion of elevation height system in engineering survey? It is a puzzling and important question. Many height systems have been formed in the history of our country, which are often different in different departments and periods. Very little information is available. First collect and sort out as follows.

(1) Baltic sea level

Baltic Sea elevation 10.374m = 1956 Yellow Sea elevation.

There are still some hydrological stations in Xinjiang, China that still use the Baltic Sea elevation.

(2) Yellow Sea elevation

It is a height system with zero average sea level based on the tidal data of Qingdao Tidal Station 1950- 1956. Origin is located in Guanxiang Mountain, Qingdao. The elevation of the origin calculated by "1956 Yellow Sea height system" is 72.289 meters.

(3) 1985 national elevation datum

Because the data series of Qingdao tide gauge station (1950 ~ 1956) for calculating this datum is short, the competent department of surveying and mapping in China decided to recalculate the average sea surface of the Yellow Sea, and based on the tide gauge data of Qingdao tide gauge station 1952 to 1979, the people in Qingdao, China were measured with precise leveling.

1985 national elevation datum elevation = 1956 Yellow Sea elevation-0.029m.

1985 national elevation datum was put into use in may of 1987, and was abolished in the yellow sea and 1956 height system.

(5) Guangzhou elevation and Pearl River elevation

Guangzhou elevation = 1985 height system +4.26 (m).

Guangzhou elevation = Huanghai height system +4.4 1 (m)

Guangzhou elevation = Pearl River elevation datum +5.00 (m)

Dalian lingdian

During the occupation of Northeast China, tidal stations were set up in the warehouse area of Dalian Port, and the average sea level obtained from many years of tidal data was zero, which was called "Dalian Zero". Height system base point is located in the east corner of No.1 Pier of Dalian Port in Dalian, Liaoning Province, and the elevation of Dalian Zero height system base point is 3.765 meters. The origin is located in People's Square, Changchun City, Jilin Province, which has been destroyed. This system was widely used in Northeast China before 1959. Northeast 1959 Precision Leveling Network was changed to height system in the Yellow Sea on 1956 after the connection between Shanhaiguan and Southeast Leveling Network was adjusted. 1956 The elevation of Dalian base point is 3.790 meters in the height system of the Yellow Sea.

(7) Waste Yellow River zero point

Jianghuai Water Resources Survey Bureau called the abandoned Yellow River estuary zero at 5 pm in the first year of the Republic of China +065438+ 10/day. After that, the bureau used the average tidal level observed for many years to determine the new zero point, and its elevation measurement was mostly based on the new zero point. The origin of height system "Abandoned Yellow River Estuary Zero" has disappeared, and there is no data on the height difference between the old zero and the new zero at the origin and the replacement time. In the "Zero Point of Abandoned Yellow River Estuary" system, there are two parallel reference leveling points, namely "Huijimen Reserve Point of Jianghuai Water Conservancy Bureau" and "Reference Point of West Jianghuai Water Conservancy Bureau of Jiangba Wharf".

(8) Kanmenling

During the period of the Republic of China, according to the tidal data of Kanmen Tide Station in Yuhuan County, Zhejiang Province for many years, the Geological Survey Bureau of the Military Command Department counted that the mean value of the station was zero, which was called "Kanmen Zero". Kanmen Tide Station has a base point of 252 and an elevation of 6.959 meters. The height system has been surveyed in Hangzhou, southern Jiangsu and northern Anhui, and has been widely used in military surveying and mapping.

Height system adopted in the original Yellow River Basin.

The height system in the Yellow River Basin is rather chaotic, and there are as many as 9 kinds of height system currently used (Dagu, Huanghai, Hypothesis, Freezing, 1985 National Elevation Datum, Leading Point III, Daowei, Kanmenmen Tidal Level, Dalian Huludao). At present, all of them have been unified into 1985 national elevation datum.

2. Wu Shu (Mouth) Height System

The height system is chaotic, and the values used in different regions are different. If adopted, it needs to be carefully checked.

Ningbo: "1985 national elevation datum" annotation point = "Wusong height system" annotation point-1.87.

Jiaxing: "1985 national elevation datum" annotation point = "Wusong height system" annotation point-1.828 (? )

Question 4: What is roadway elevation measurement? The purpose of roadway elevation measurement is to establish underground elevation control system, and then determine the elevation of underground traverse points and elevation points, as well as the elevation of roadway and cavern, so as to guide mine excavation construction and achieve the purpose of filling elevation notes on mine maps.

Question 5: How to measure the elevation? What is the detailed formula? What is altitude? Method one

With a level, look back at the reading first, that is, put the tower ruler on the leveling point with known elevation and read the reading (as a look back reading); Then put the tower ruler on the point to be measured and read each other's readings (recorded as positive readings). The formula is: elevation of rear viewpoint+rear reading-front reading = elevation of the point you want to measure.

Method 2

Using total station, the difference is that the instrument height and prism height should be set when measuring, and then the backward reading and forward reading should be measured in the same way. The formula is: elevation angle of rear viewpoint-rear reading+front reading.

Question 6: What are the main methods of elevation control survey? The method you adopt depends on your main purpose. At present, there are three main methods of elevation control survey:

1, leveling

2, trigonometric leveling

3.GPS height measurement

Question 7: What is the measurement benchmark in China? Including geodesy and elevation survey 1954 Beijing coordinate system,1980xian coordinate system and 2000 national coordinate system. 1956 Yellow Sea height system, 1985 National Elevation Datum.