Surveying

6 steps to caring for surveying instruments

1. keep the instrument protected from the rain & dust, in the case when not in use 2. protect the instrument with the waterproof cloth if it must remain standing during wet weather 3. always spread the tripod legs wide and press them firmly into ground 4. never rub dust off the lens, blow or brush lens lightly 5. when setting up the instrument on a smooth surface use a wooden triangle or some other such device to secure the legs 6. always transport the instrument with the greatest of care

5 steps for plumbing a column or post

1. set up instrument in appropriate position for best view of column 2. sight in the edge of the column to be plumbed at the bottom of the object 3. lock the horizontal lock nuts & pin point the edge by using the horizontal adjusting screw 4. tilt the scope toward the top of the column 5. if the edge of the column corresponds with the L.S. the column is plumb; if not move the top of the column in the appropriate direction until it is in the L.S.

upper clamp

a clamp that is manipulated to set and hold the line of sight of the transit on the foresight point or a clamp that is tightened to hold the upper plate in a fixed position clamped to the lower plate

vertical clamp

a clamp used to set and hold the line of sight at a desired vertical angle to be measured or laid off

profile leveling

a combination of differential leveling and rod shots, used to obtain a representation of the ground surface

profile

a continuous representation of the ground surface

hub

a corner stake or reference point used to establish elevations or other reference points

level vial

a curved container partly filled with liquid used to determine horizontal or level direction

bench mark (B.M.)

a definite point of permanent character whose elevation and location are known

construction layout

a design that shows the exact location where a builder is to place the finished construction

survey party

a group of people who go into the field to take on-the-spot measurements and record them

datum plane

a horizontal plane used as a reference point in determining vertical locations or elevations of other points

line of sight (L.S.)

a level line sighted through a telescope in any given direction

plumb

a line which is exactly vertical or perpendicular to a level horizontal line

property map

a map on which the boundaries of a piece of property are recorded after they have been determined by surveying methods

plot plan

a map that shows the location and relationships of all existing objects on a certain piece of property

target

a moveable disc mounted on a level rod and used to make reading the rod easier and more accurate

quadrant

a quarter of a circle

upper tangent screw

a screw that is manipulated for fine adjustment of the setting of the upper plate or a screw that is manipulated to bring the cross hairs of the telescope exactly on the foresight point

vertical tangent screw

a screw that is manipulated to bring the cross hairs of the telescope exactly on the point for measuring or laying off a vertical angles or a screw used to train the telescope cross hairs exactly on the object after the motion of the vertical vernier has been stopped

level circuit

a series of sightings from one point to another to measure the distance in elevation between the two points, and a return trip with sightings from different locations to check the accuracy of the measurement

cross section

a short profile perpendicular to the line of work

vernier

a short sliding scale on a level rod target that permits reading to thousandths of a foot or on a transit, one of the auxiliary scales calibrated in subdivisions of degrees and used for measuring angles

surveyor's pin

a straight wire with a point at one end and a circular eye at the other driven into the ground to mark a temporary or intermediate measuring point

preliminary survey

a survey made prior to designing a construction project to determine the shape of existing objects and their relationships to each other

range pole

a tall pole set up beyond the forward point to help the tape persons keep measurements of separate tape lengths in a straight line

standard tape

a tape that is certified by the Bureau or Standards and that is used to check working tapes

turning point (T.P.)

a temporary, intermediate point for which the elevation is measured in the process of running a level circuit

tripod

a three-legged supporting stand

level rod

a two-section wooden rod calibrated with graduations of either feet or meters, on which readings of vertical distances are taken

plane surveying

a type of surveying used in small areas where sufficient accuracy is obtained without taking into account the curvature of the earth

geodetic surveying

a type of surveying which takes into account the curvature of the earth

minute

a unit of angular measure equal to the sixtieth part of a degree

stationing

a variation of the coordinate method used for long narrow projects such as pipelines and highways

raise for red

a verbal signal used to request the rod person to raise the rod for a check on the reading

plumb bob

a weight on the end of a string; this device is used to indicate vertical direction, or the direction in which gravity acts

plumbing up

aligning the plumb bob and string until the bob hangs motionless directly over the point of measurement

transit

an instrument used primarily to measure horizontal and vertical angles

stadia hairs

are the lines in the instrument eye piece, used to calculate distance from the instrument to the rod

4 types of levels

builder's level, dumpy level, automatic level, laser level

horizontal angles

building lines that are established at an angle to another building line

turning an angle

defining an angle by rotating the revolving line of the angle a certain distance horizontally or vertically about the vertex

3 types of transits

engineer's transit, combination level transit, optical plummet transit

systematic errors

errors that accumulate in the same direction

rod shots

extra shots taken from an instrument set up in the same way that a foresight is taken on a turning point

origin

in a coordinate system, the point at which the x axis crosses the y axis

station

in differential leveling, the point on which the rod stands when it is read

back sight (B.S.)

in leveling, a reading taken on a point of known elevation; or a reading taken in the direction from which the survey is proceeding; also called a plus sight

fore sight (F.S.)

in leveling, a reading taken on a point of unknown elevation; or a reading taken in the direction toward which the survey is proceeding; also called a minus sight

mistakes

inaccuracies caused by incorrectly or carelessly performed operations

leveling screws

on an engineer's level, the screws that are manipulated to obtain a level line of sight through the telescope

second

one 60th part of one minute of one degree

cosine

one of the trigonometric functions used to relate the angles of a right triangle to the lengths of the sides of the same triangle (cosine = adjacent over hypotenuse)

sine

one of the trigonometric functions used to relate the angles of a right triangle to the lengths of the sides of the same triangle (since = opposite over hypotenuse)

tangent

one of the trigonometric functions used to relate the angles of a right triangle to the lengths of the sides of the same triangle (tangent = opposite over adjacent)

stations

points set 100 feet apart along a baseline

latitude

shown as horizontal lines, is the angular distance in degrees, minutes and seconds of a point north or south of the equator

longitude

shown as vertical lines, is the angular distance in degrees, minutes and seconds of a point east or west of the Prime Meridian

magnetic north

the approximate north direction indicated by a compass

vertical vernier

the calibrated vertical circle and auxiliary scale attached to the telescope and to measure vertical angles

vertex

the common point from which the two or more lines meet

accuracy

the conformity of a measurement to the true value

vertical direction

the direction in which gravity acts; a line toward the center of the earth

true north

the direction of the North Pole from a given point

elevation

the distance that an object is located above a specified reference point or the height of any point above mean sea level

height of instrument (H.I.)

the elevation of an instrument location, calculated by adding the back sight reading to the elevation of a benchmark or turning point

degree

the principal unit of measure for angles

setting a back sight

the procedure of setting a point along a fore sight from one hub when that hub will not be visible from the next hub; the point set will serve as the back sight in measuring the next angle

differential leveling

the process of determining the difference in elevation between two points by taking multiple sightings from a series of instrument setups between the points

cross section of leveling

the process of taking rod shots at specified distances from the centerline and at right angles to the centerline

surveying

the science of determining the relative positions of point on, under or near the earth's surface

construction stakeout

the setting of marked stakes in the ground at the locations where various parts of a planned construction are to be built

leveling

the surveying procedure dealing with elevations and vertical distances

upper plate

the top of a transit, also called alidade

vernier A and B

two scales, 180 degrees apart on the edge of the upper plate, used to measure horizontal angles