What is elevation closure and what is elevation closure difference?

In order to ensure the accuracy of the measurement, it is generally necessary to attach from one leveling point to another leveling point in the measurement process, or to measure from a leveling point to the point to be measured, and then map to the leveling point, which is called attaching or closing leveling. On the construction site, everyone usually measures in a closed area.

What is the elevation closure difference: it is the height difference value generated only when it is attached from a leveling point to another leveling point, or from a leveling point to the point to be measured, and then surveyed to the leveling point.

Generally, the review of whether the measurement results are effective, that is, whether the closure difference is less than plus or minus 30 times l square (l is the mileage) unit is mm, such as 500m, then l =, I don't know if the current specification has changed. For example: you measure a circle to measure the level point you want to close, and calculate a measurement height difference through the height difference, the actual elevation is, so that your closure difference is +10mm, this circle is about 1000m, then the allowable error is 30 * 1 square = 30mm, 10 is less than 30, the measurement data is valid, otherwise it is invalid and needs to be re-measured.

The sum of the measured elevation differences is not equal to the theoretical value or the difference in elevation between the two known points to which they are attached.

It should be the elevation closure difference.

Elevation refers to the distance from a point along the plumb line to the absolute base plane, which is called absolute elevation. Abbreviated as elevation. The distance from a point along the plumb line to a hypothetical horizontal base is called the hypothetical elevation.

"Elevation" is a surveying and mapping word, and in popular understanding, elevation is actually altitude.

Closure Error: This is the error that occurs during the closure measurement.

Sweat! It's all in one.

Errors in closed measurements of altitude.

The height difference closure difference is the end of the horizontal routeLeveling pointsThe difference between the known elevation value and the extrapolated value derived from the sum of the known elevations of the starting level point and the elevation difference of all stations.

Calculation method Zheng Chao:

Due to the existence of measurement errors such as instrument (tool) errors, observation errors, and the influence of external conditions, it is measured at the level.

Measurement errors inevitably occur. When the cluster point to be measured is far away from the known point, after the observation of multiple stations, a certain error must be accumulated on the point to be measured, and the amount of these errors can only be known through redundant observation.

Redundant observations are reflected here as observations of the end point. The measured elevation of the end point is compared with the theoretical elevation of the end point to know how much error is generated, which is the height difference closure error.

The results of the leveling measurement are checked, and when the measurement error is within the allowable range, the resulting measurement error, that is, the height difference closure difference, must be adjusted, which is the adjustment in the control measurement.

The height difference closure difference is to determine the spatial position, distance x, direction y, and elevation h of a point in the process of construction surveying in the process of construction civil engineering surveying. Errors in the measurement of elevation h.

In the field, this formula can be used to check the quality of the field and determine whether to end the field. The formula used to calculate the height difference closure difference of the three leveling routes is as follows: closed leveling route, branch leveling route:

fh=∑a-∑b。Attaching to the level route: fh = a- b- (h begins with h ends).

The above formula is relatively abstract, if the concept of height difference closure difference is concretized, we must start from the concept of height difference, and further derive the formula: fh= h measurement h theory rubber nucleus (h final test h beginning) (h final measure h beginning) h final test h final reason. As can be seen from the formula, the height difference closure difference is the difference between the measured elevation of the end point and the theoretical elevation of the end point.

Introduction

In the adjustment of the closure difference: determine whether the last correction number is stupid and the calculated height difference closure error is equal in size and the sign is opposite, otherwise the corrected elevation calculation is not allowed. For example, the last correction number is equal to the height difference closure fh=equal in magnitude and opposite in sign.

In the calculation of elevation: determine whether the corrected end elevation is equal to the theoretical value. For example, the corrected end elevation is equal to the known elevation m of the end point 6, so that the adjustment result is correct.

First of all, the height difference of the closed horizontal route must be within the allowable error range, and then first calculate the total lead of your closed horizontal route, which is the sum of all the rear and front distances, and then the number of corrections at each station is equal to (the total length of the error horizontal route * the sum of the front and rear socks and acres of the apparent distance * -1), the reason why it is best to multiply it by -1, because the final calculated correction number is the opposite sign and distributed to each station, okay?

Let's start by explaining the "height difference correction number":

Using the same instrument and the same measurement method on the same leveling route, it can be considered that the chance of error at each station is equal.

Therefore, the height difference closure difference can be proportional to the number of elevation differences in each measurement section according to the number of stations n1 (or according to the distance l1) in proportion to the number of elevation differences, which is called the elevation difference correction number.

i.e.: i=-fh n*n i or i=-fh n*li

Let's talk about how to calculate the height difference closure difference:

The difference between the "known value" of the leveling point at the end of the leveling alignment and the estimated value obtained from the "sum of the known elevations and the elevation difference of all stations" at the starting leveling point.

To put it simply, each elevation measurement is h2 = h1 + (h rear view - h front view).

N observations have n h rear view - h front view.

Then (h2-h1) -h rear view - h front view) is the height difference closure difference.

Due to the instrumental error, observation error and external influence in leveling, there are inevitably errors in leveling, and the height difference closure difference is a comprehensive reflection of the influence of each error in the leveling observation error. Calculation method: 1. The algebraic sum of the algebraic sum of the sum of the height difference between the past and the back measurement should be equal to zero in theory, but due to the influence of various errors in the measurement, the algebraic sum of the sum of the height difference between the past and the return is not equal to zero, that is, there is a height difference closure difference = h to + h back 2, the closed level route, because the starting point and the end point are the same point, It forms a closed loop, so the sum of the height difference of each section measured by the closed horizontal route should theoretically be equal to zero, that is, h theory = 0.

The sum of the height difference of each measurement section actually measured by the buried banquet travel closed level route is H measurement, and its height difference closure difference = h measurement - H 3, the attached level route, because the elevation of the starting point A and the end point B HA and HB are known, the height difference between the two points is a fixed value, and the difference between the sum of the height difference of each measurement section measured by the attached level route and the theoretical value of the height difference is the height difference closure difference of the attached level route = h measurement - (HB-HA) When the height difference closure difference is within the allowable range, the distribution of the height difference closure difference can be carried out, The principle of distribution is: for the closed or attached horizontal route, according to the principle that it is proportional to the length of the route l or the number of stations n of the route, the closed difference of the elevation difference is distributed against its sign.

Height difference closure error and allowable closure error are two concepts commonly used in measurement engineering, and their differences are as follows:

1.Elevation Difference Closure Difference: The height difference closure difference refers to the ridge source difference between the sum of the measured height difference and the sum of the theoretically obtained height difference in the process of returning to the starting point on a closed horizontal line.

Height difference closure is a metric used to assess the precision and accuracy of leveling, usually in millimeters or centimeters.

2.Allowable Closure Difference: The allowable closure error refers to the maximum allowable closure difference on a closed measurement line of the Divine Oak according to the measurement accuracy and requirements.

The permissible closure error is determined based on specific measurement requirements and engineering standards, usually in millimeters or centimeters. If the actual measurement results in a closure error that is less than or equal to the allowable closure error, the measurement result is considered acceptable.

In short, the height difference closure difference is the difference between the actual measured height difference and the theoretical height difference, which is used to evaluate the accuracy of the measurement; The allowable closure error is the maximum allowable closure error according to the specific requirements and standards, which is used to judge whether the measurement result is acceptable.

The definition is not the same as the calculation.

1. Definitions. The height difference closure difference is the level point at the end of the level route.

The difference between the known elevation value and the extrapolated value derived from the sum of the known elevations of the starting level point and the elevation difference of all stations. The permissible closure error is the difference between the observation of a certain quantity and its due value.

2. Definitions. Elevation difference He Qing talks about the closing difference = the difference between the sum of the cumulative elevation difference of the horizontal line and the difference between the elevation difference of the starting point and the final Zen touching point. The allowable closure error is calculated by fx=h.