Shows how to use a transit to locate a building correctly on the lot, plan proper grades with minimum excavation, find Building Layout Author, W.P. Jackson. Building Layout,WP Jackson. Shows how to use a transit, to locate a building correctly on the lot, plan grades with minimum excavation, find utility lines. : Building Layout () by W. P. Jackson and a great selection of similar New, Used and Collectible Books available now at great.

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The list can include farmers, buildig and many others. If the radius is large, a small vertical movement on one end of the tube causes a large displacement of the bubble. Plumbers need them to lay out sewer lines.

Sensitivity in seconds ” per 2mm division of level tube Radius of curvature in feet 14′ ” 1′-7″ 8′ ” 2′” ” 13′-6″ 90″ 15′ 75″ 18′ 60″ 23′ 45″ 30′ 30″ 45′ 20″ 68′ Radii of Level Tubes of Different Sensitivities Table Level tube sensitivity is normally given as the number of seconds of arc per 2 mm division on the tube. The TAT theodolite reads directly to 20 seconds on the optical micrometer. Jackson There is no substitute for accurate layout of foundations, walls and floors.

In most units, the markings on the level tubes are 2 mm apart. Instead it will be centered over another point, a, resulting in an erroneous reading. Theodolites are used where precision work is essential. You must then reposition the tripod.

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A 26x instrument may be used for work up to feet. Masons need them to level walls and foundations. The greater the precision of the transit, the more sensitive is the level tube built into it. Level Tube Sensitivity The more sensitive the level tube, the greater the precision that may be obtained.


More and layoyt trades are using them to save time, cut costs, and insure accuracy in their work. Chapter 1 The Transit A transit is used to measure horizontal and vertical angles. Figure shows biilding principle of the optical plummet. The variable powers of the zoom lens type depend on the model of the instrument; some adjust from 18x to 34x, others from 24x to 37x.

They will not be covered here, but you should know the reason for some of the operations and how they can affect the accuracy of your work. If the radius is small, the same vertical movement causes only a small displacement of the bubble. You don’t need an engineering degree or any technical knowledge to use one.

Make sure your instrument is in w.p.jsckson adjustment before you follow the instructions below. But if it is not set up and leveled properly, accurate work is impossible regardless of how accurate the instrument is.

The more sensitive the level tube, the longer it takes to center the bubble.

The optical plummet serves the same purpose as a plumb bob, but is more accurate because it is not affected by the wind. A tube with a sensitivity reading of 8 minutes seconds would form an angle of 08′ 00″ at a radius of 2 feet 10 inches 2′” with each 2 mm movement of the bubble.

Line a-b is parallel to the line of collimation of the telescope and is perpendicular to b-cwhich is the ray of light from the right angle prism at b to the target at c. Instruments designed for still greater precision have a vernier that further subdivides each minute into seconds. The power of the telescope can vary.

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It is marked in degrees and has a vernier scale that subdivides each degree w.p.jacksin minutes on the better models. Crosshairs in the telescope permit the object sighted to be centered in the field of view. Leveling is the most important operation you perform before you use your instrument. These are extremely precise instruments.


The right transit for you depends on your job requirements. A bubble that travels more with small movement takes longer to settle with each movement of the leveling screw. A vial with a sensitivity of 45 seconds ” per 2 mm is more sensitive than one with a 90 seconds ” per 2 mm sensitivity. A theodolite is essentially a more precise transit. The operation of a builder’s transit or transit-level is not complicated. Level tubes are ground to specific w.p.jafkson.

This means that for each 2 mm the bubble moves in the tube, it forms an angle equal to the sensitivity of the arc given. Figure shows a transit with a 20 second vernier reading. The vertical axis is not centered over A, even though the plumb bob might be. If the center of the tripod head is not approximately over the point, centering the transit with the plumb bob or optical plummet isn’t possible.

Thus the radius of the tube is a measure of w.pj.ackson sensitivity. The more sensitive the level tube, the greater the precision that may be obtained.

The degree of magnification of a telescope is called its power x. The builder’s or contractor’s transit, or transit-level, does not normally include a compass because buildings are laid out from an existing fixed point at or near the building site, such as the lot corner stake or monument. Figure shows a serious error due to an instrument out of level. See Figures and You may not need that degree of precision now, but you probably will need it later when your skills increase and you take on other types of jobs.

Set the tripod on firm ground and make sure the tripod points are stuck well into the ground.