Measuring of Vertical Distances Flashcards
the commonly employed method of determining the elevation of points some distance apart by a series of set ups of a leveling instrument along a selected route.
Direct or spirit leveling
the process of accurately determining the difference in elevation between two intervisible points located at a considerable distance apart and between which points leveling could not be performed in the usual manner.
Reciprocal leveling
used to determine differences in elevation between points at designated short
measured intervals along an established line to provide data from which a vertical section of the ground surface can be plotted.
Profile leveling
employed in determining by trigonometric computations the
difference in elevation between two points from measurements of its horizontal or slope distance and the vertical angle between the points.
Trigonometric leveling
combines features of direct leveling with those of trigonometric leveling. It
can provide reasonable accuracy for preliminary surveys, mapping, and rough leveling where quick measurements are needed.
Stadia leveling
involves the determination of the differences in elevation between
points by measuring the variation in atmospheric pressure at each point by means of a barometer.
Barometric leveling
Short profiles at right angles to the line of work are usually plotted at
regular intervals for this purpose.
Cross-section leveling
method of determining the relative elevations of points in borrow-pit
excavations for the purpose of calculating volumes of earthwork.
Borrow-pit leveling
It is the most widely used direct leveling instrument. It has a long telescope
which is rigidly attached to the level bar.
Dumpy level
It has a detachable telescope which rests in supports called wyes. It can be removed from the Y-shaped supports and turned end for end during adjustment by releasing the two clamping collars which fit across the tops of the Y’s.
Wye level
used primarily in the different phases of building construction where a high
degree of precision is not a primary requisite.
Builder’s level
It has become popular for conventional leveling work because of the ease
and speed of their operation. It does not use a level vial and its ability to level itself depends upon the action of a complex pendulum-and-prism device.
Automatic level
commonly employed for very precise leveling operations and in other general leveling work.
Tilting level
employed in first-order leveling work where extreme precision is an important requirement. It is equipped with stadia hairs in addition to the standard vertical and horizontal cross hairs to make it suitable for three-wire leveling.
Geodetic level
universal surveying instrument. It can provide results which are fairly precise although not as good as those obtained with conventional levels.
Transit
A laser system is a separate unit equipped with a portable power supply and may be a helium-neon or gas laser.
Laser level
a hand-held instrument used on surveys involving short sights and where a low order of accuracy is sufficient.
Hand level
a graduated rod which is used for measuring the vertical distance between the line of sight through a leveling instrument and the point whose elevation is either required or known.
Leveling rod
a device used for fast and correct plumbing of a leveling rod. It is L-shaped in design and consists of a small circular spirit level fastened to the rod or to a small bracket held against the side of the rod.
Rod level
a small device attached to the rod when extremely long sights make direct reading of the rod
difficult or impossible.
Target
a metal tube containing a system of lenses which are used to fix the direction of the line sight and in magnifying the apparent size of objects in its field of view. Jan Lippershey, a
Dutchman, invented the first _____________ in 1608.
Telescope
a compound lens composed of crown and flint glass mounted in the objective end of the telescope and has its optical axis concentric with the tube axis.
Objective lens
a form of microscope containing either two or four lenses and is used to enlarge altogether the image and the cross hairs.
Eyepiece
consist of a pair of lines which are perpendicular to each other and are used to
define the instrument’s line of sight.
Cross hairs
the ratio of the apparent size of an object viewed through a telescope to its size as seen by the unaided eye from the same distance.
Magnification
a sealed graduated glass tube containing some amount of liquid and a small air bubble.
Level vial
used on most modern and precise instruments such as the tilting and automatic
levels. It employs an optical device which splits the bubble longitudinally, then turns one end around to make it appear adjacent to the other end.
Coincidence bubble
serve as abase to prevent movement of the instrument after it is set up.
Tripods
Steps in taking a rod reading.
- Position the rod
- Focus on the rod
- Read the rod
