Differential leveling

This is the preferred method for setting or checking control bench marks. The method in Figure uses the difference in elevation between a known elevation and the height of the instrument, and then the difference in elevation from the height of instrument to an unknown elevation point.

Differential Leveling Overview

All rods should be checked and maintained to ensure consistent readings. Three-Wire Leveling Three-wire leveling is the process of reading and recording a rod reading for each of the three horizontal cross-hairs on each shot, then averaging the readings for agreement with the center reading.

Advanced capabilities include automatic measurement of height and distance by reading a barcode rod, high precision by employing image processing technology, data display and data recording either internally or to a data collector, installed software for elevation stake-out or other leveling procedures.

The utility of differential leveling is described in the name. Any time that high scintillation is observed between the level and the rod, sight distances must be reduced. Equipment The Rod Rods are, in essence, a tape supported vertically, and used to measure the vertical distance difference of elevation between a horizontal line of sight and a required point above or below it.

If not, have the instrument serviced. Temporary bench marks set in trees or power poles should consist of a spike railroad spike, boat spike, or large nail spike set horizontally approximately 1 to 2 ft.

Turning points should be marked when used so as to insure that the rod is in the exact same place when the backsight and foresight are taken.

Do not make observations on the rod higher than the project specifications require. A thorough knowledge of Differential leveling principles and proper application of methods and equipment will prevent costly delays and generate the needed results and accuracy.

Maximum sight distance — care should always be given to observe recommended or required distance of sight, depending on the purpose of leveling. Manufactured points for example, the marlinspike and the base plate or turtle can be used.

Temporary bench marks set in trees or power poles should consist of a spike railroad spike, boat spike, or large nail spike set horizontally approximately 1 to 2 ft. This is the preferred method for setting or checking control bench marks.

Leveling should be avoided during hot temperatures. The rodmen hold the level rod; pace the sight distances between the instrument and the level rod to ensure that the minimum inequalities of the setup and the accumulated sight distances are maintained; hold the rod during readings in a plumb and steady vertical position using the handles of the rod; place the rod in precisely the same position for the backsight as it was for the foresight; carry the rod using the handles not over the shoulder ; and ensure that the rod face, the sole of the rod, and the circular bubble do not contact the ground or receive a sudden shock the level rod is a precise-survey instrument and must be treated as such.

Temporary bench marks can be turning points that remain or additional intermediate bench marks placed for added convenience. An electronic digital level can perform and record this process automatically, after sight of the rod is made.

Field operations for optical-micrometer leveling are nearly the same as for three-wire leveling except that optical-micrometer leveling uses double-scale invar rods and shorter sight distances.

Leapfrog the rods forward. An electronic digital level can perform and record this process automatically, after sight of the rod is made.

Turning points should be marked when used so as to insure that the rod is in the exact same place when the backsight and foresight are taken. The most common methods to determine elevation are through the use of 1 a compensator type, automatic engineering level and level rod sand 2 an electronic digital barcode leveling instrument with barcode rod.

The Level The compensator type, automatic engineer level is made by various manufacturers, and is a precision, self-leveling instrument, equipped with a built-in compensator that automatically maintains a horizontal line of sight and has a telescope with approximately power magnification.

Follow these steps when performing third-order differential leveling: The sole of the rod is placed on the BM or a temporary turning point.

Differential Leveling Overview

Turning points should be marked when used so as to insure that the rod is in the exact same place when the backsight and foresight are taken. The sole of the rods are made of a metal base, machined for accuracy. Chapter 7 Differential Leveling Differential leveling is a technique used to determine differences in elevation between points that are remote from each other.

They must be solid, well defined or marked and permanent enough to remain intact until the level loop is finished. They should be positioned so as to be usable from a wide area and away from the construction as much a possible so as to remain undisturbed.

Due to the number of small systematic errors that are not discernible from geometric checks, it is imperative to adhere to the prescribed procedures. Leveling Tolerance See Table 4. Equipment The Rod Rods are, in essence, a tape supported vertically, and used to measure the vertical distance difference of elevation between a horizontal line of sight and a required point above or below it.

Automated data collection eliminates transposition errors and data is downloaded into a computer for complete analysis.

All leveling equipment must be checked regularly and properly maintained to ensure that it remains in proper working condition and that systematic errors are eliminated to produce the expected results. The most common methods to determine elevation are through the use of 1 a compensator type, automatic engineering level and level rod sand 2 an electronic digital barcode leveling instrument with barcode rod.

The table used for differential leveling data uses columns and rows. With a compensator type, automatic level, observe the compensator while adjusting level screws to make sure that motion is smooth.

The level mounts on a standard surveying tripod, or a fixed-leg tripod for more precise leveling. These bench marks should be identified, confirmed undisturbed, and elevations proved by running a complete level loop between the two, returning to the starting bench mark.

Other forms of leveling are available but are not discussed in this manual as they are not preferred or their use may be limited.differential leveling, based on the particular needs of the survey task being performed.

When developing procedures consider the following: objective of task, specific needs. Section 2: Differential Leveling Anchor: #i Overview. Differential leveling is the process of measuring vertical distances from a known elevation point to determine elevations of unknown points.

Illustration of Differential Leveling. The method in Figure uses the difference in elevation between a known elevation and the height of the instrument, and then the difference in elevation from the height of instrument to an unknown elevation point.

DIFFERENTIAL LEVELING DEFINITION OF DIFFERENTIAL LEVELING The establishment of differences in elevation between two or more points with respect to a. For differential leveling, the only critical feature of station identification is that an organized method be used so that the system is clear to the user of the notes.

differential leveling

In differential leveling, each station is used as a backsight and a foresight. definition of differential leveling The establishment of differences in elevation between two or more points with respect to a datum. Normally we will assign an elevation of to the datum rather using the mean sea level elevation.

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Differential leveling
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