Surveying Base Knowledge

What is a contour?

A line connecting points of equal elevation.

Assumed

A value of 0∘ arbitrarily assigned to a line on the ground

Describe how parallax in the viewing system of a level can be detected and removed.

After focusing, if the cross hairs appear to travel over the object sighted when the eye is shifted slightly in any direction, parallax exists. The objective lens, the eyepiece, or both must be refocused to eliminate this effect if accurate work is to be done.

Discuss how errors due to Earth curvature and refraction can be eliminated from the differential leveling process.

Balancing plus and minus sight distances will eliminate errors due to instrument maladjustment and the combined effects of the Earth's curvature and refraction.

How can collimation error be removed from the differential leveling process?

Collimation error is a systemic error that can be eliminated by balancing the backsight and foresight distances between benchmarks.

What is the collimation error?

Collimation error is caused by the line of sight not being parallel with the axis of the level vial. When this condition exists, the line of sight will not be horizontal and thus result in incorrect readings.

Why are the boundaries of the public lands established by duly appointed surveyors unchangeable, even though incorrectly set in the original surveys?

Correcting mistakes now would disrupt accepted property lines and result in lawsuits.

Why are lot-and-block descriptions not subject to junior and senior rights?

Lot-and-block descriptions typically are created simultaneously and thus are not subject to junior and senior rights.

Define map scale.

Map scale is the ratio of the length of a feature on the map to the true length of the feature.

List the disadvantages of an open traverse.

Observations need to be repeated to guard against mistakes. It offers no means of checking for observational errors. Lines do not close upon a point of equal or greater order accuracy.

Explain how aerial photographs and satellite images can be valuable in surveying.

Photogrammetry presently has many applications in surveying. It is used, for example, in land surveying to compute coordinates of section corners, boundary corners, or points of evidence that help locate these corners. Large-scale maps are made by photogrammetric procedures for many uses, one being subdivision design. Photogrammetry is used to map shorelines, in hydrographic surveying, to determine precise ground coordinates of points in control surveying, and to develop maps and cross sections for route and engineering surveys. Photogrammetry is playing an important role in developing the necessary data for modern Land and Geographic Information Systems.

What is the difference between a planimetric and topographic map?

Planimetric depicts natural and cultural features in the plan ( X - Y ) views only. Objects displayed are called planimetric features. Topographic maps show the configuration of the Earth's surface.

What is the name of the state-level professional surveying organization in your state or region?

Professional Land Surveyors of Ohio

Grid

Reference meridian chosen from some map projection system such as the state plane coordinate system where all meridians are parallel to the central meridian of the projection.

Record or deed

Reference meridian selected from a recorded deed by using the value given for one line in the deed.

Magnetic

Reference meridian taken from current position of magnetic poles.

Astronomic

Reference meridians taken from instantaneous position of Earth's pole, which wanders over time.

Geodetic or true

Reference to geodetic north, which is referenced to the average position of the poles between 1900.0 and 1905.0.

Discuss the criteria to consider when making reference ties to traverse stations.

Short lengths (less than 100 f t ) are convenient if a steel tape is being used, but, of course, the distance to definite and unique points is a controlling factor. two ties, preferably at about right angles to each other, are sufficient, but three should be used to allow for the possibility that one reference mark may be destroyed. Ties to trees can be observed in hundredths of a foot if nails are driven into them. However, permission must be obtained from the landowner before driving nails into trees.

List five types of common errors in taping.

Tape not level Tape length Plumbing Marking Temperature

plumb line

The direction is considered parallel throughout the survey region

In a description by metes and bounds, what purpose may be served by the phrase "more or less" following the acreage?

The expression 'more or less,' which may follow a computed area, allows for minor errors, and avoids nuisance suits for insignificant variations.

What is the relationship of a forward and back azimuth?

The forward direction of a line can be given by its forward azimuth, and its reverse direction by its back azimuth. In plane surveying, forward azimuths are converted to back azimuths, and vice versa, by adding or subtracting 180 ∘ .

What is a contour interval?

The vertical distance between consecutive level surfaces forming the contours on a map.

NAVD88

This adjustment (NAVD88) shifted the position of the reference surface from the mean of the 26 tidal gage stations to a single tidal gage benchmark called Father Point, which is in Rimouski, Quebec, Canada, near the mouth of the St. Lawrence Seaway. Thus, elevations in NAVD88 are no longer referenced to mean sea level. Benchmark elevations that were defined by the NGVD29 datum have changed by relatively small, but nevertheless significant amounts in the eastern half of the continental United States. However, the changes are much greater in the western part of the country and reach 1.5 m in the Rocky Mountain region. It is therefore imperative that surveyors positively identify the datum to which their elevations are referred. After the adjustment, adjusted elevations are properly known as orthometric heights.

What is the point of beginning in a property description?

This point must be identifiable, permanent, well referenced, and one of the property corners. Coordinates, preferably state plane, should be given if known or computable. Note that a point of beginning is no more important than others and a called for monument in place at the next corner establishes its position, even though bearing and distance calls to it may not agree.

Why is it important to make accurate surveys of underground utilities?

To provide an accurate record of the locations of these utilities so they can be found if repairs or servicing is needed, and to prevent their accidental destruction during excavation for other projects.

Identify two surveying examples of a systematic error.

Using a tape measure that has been stretched due to use. Using an instrument support that changes length with temperature.

examples of a random error.

Using an elevation rod in windy conditions that cause it to lean. Interpolating hundredths on a tape graduated only to tenths.

In what states are public land surveys not applicable?

West Virginia Maine Kentucky Vermont the original 13 colonies Tennessee Texas Hawaii

level surface

a curved surface that at every point is perpendicular to the local plumb line (the direction in which gravity acts).

vertical line

a line that follows the local direction of gravity as indicated by a plumb line

turning point

a point between benchmarks which are created to perform the differential leveling process. They are usually temporary points whose elevations are lost after the differential leveling process is complete.

benchmark

a relatively permanent object , natural or artificial, having a marked point whose elevation above or below a reference datum is known or assumed.

Define aliquot part.

a smaller subdivision of a Section in the U.S. Public Land Survey System

Systematic errors

also known as biases, result from factors that comprise the "measuring system" and include the environment, instrument, and observer.

List 10 uses for surveying in areas other than land surveying.

control, alignment, aerial, optical, as-built, satellite, topographic, mine, solar, construction

English Units

cu. ft. yd. sq. mi. acres

stadia method

determines the horizontal distance to points through the use of readings on the upper and lower (stadia) wires on the reticle. The method is based on the principle that in similar triangles, corresponding sides are proportional.

In performing retracement surveys, list in their order of importance, the four different types of measurements called for in a description for most states.

distance direction area coordinates

SI Units

hectare cu. m m sq. km

Precision

is the degree of refinement or consistency of a group of observations and is evaluated on the basis of discrepancy size.

Accuracy

is the nearness of the observed quantities to the true value, which is never known.

indirect measurement

measuring refractive index of a medium by the angle of deflection of light entering the medium measuring density of an object with known mass and volume measuring the velocity of a car that has traveled 50 miles in 1 hour measuring the mass of the sun knowing the strength of its gravitational field at a point whose distance from the sun's center is known measuring the charge of a conducting sphere knowing the strength of its electric field at a point whose distance from the sphere's center is known

direct measurement

measuring the length of a board with a meter stick measuring the volume of a liquid in a beaker measuring mass the mass of a lead cube on a scale measuring temperature in a room measuring the pressure of air in a tire

Describe the steps a land surveyor would need to do when performing a boundary survey.

preliminary walking of property with owner courthouse research to locate deed of property and adjoiners to determine ownership, possible easements, right-of-ways, conflicts of interest, and so on location survey of property noting any encroachments; conflicting elements; and so on resolution of conflicting elements between deed and survey delivery of surveying report to owner

measured angles

presumed to be plane angles

List the three basic requirements in determining an angle.

reference line direction of turning angular distance

benchmark

relatively permanent object, natural or artificial, having a marked point whose elevation above or below a reference datum is known and fixed

List in their order of importance the following types of evidence when conducting retracement surveys:

senior rights intent of the parties call for survey monuments measurements least important

List the possible errors that can occur when measuring a distance with an EDM.

temperature corner cube reflectors pressure setup of EDM instruments faulty measurements of instrument and reflector height

differential leveling

the actual sight distances to the rod are not important. All one needs to balance is the rod intervals on the plus and minus sights between benchmarks to ensure that the sight distances are balanced

geodetic surveys

the curved surface of the earth is considered by performing the computations on an ellipsoid (curve surface approximating the size and shape of the earth)

residual

the difference between the observed value of a quantity and the mean of the observed values, v = bar M - M.

error

the difference between the observed value of a quantity and the true value, E=X−Xbar

D=KI(5.2)

the equation for a distance on a horizontal stadia sight

plane surveys

the reference base for fieldwork and computations is assumed to be a flat horizontal surface

Random errors

those that remain in measured values after mistakes and systematic errors have been eliminated. They are caused by factors beyond the control of the observer, obey the laws of probability, and are sometimes called accidental errors. They are present in all surveying observations.

Topographic surveys

used whenever elevation data is required in the end product. examples include (1) creating maps for highway design; (2) creating maps for construction surveys; (3) creating maps for flood plain delineation; (4) creating maps for site location of buildings; and so on.

List the five types of measurements that form the basis of traditional plane surveying.

vertical distances, vertical (altitude or zenith) angles, slope (or slant) distances, horizontal angles, horizontal distances