INTRODUCTION TO SURVEYING

SURVEYING:

The art, science, and technology of detecting the relative position of points at, above, or below the surface of the earth or establishing such points.

SURVEYING MEASUREMENT:

The art, science and technology of gathering and analyzing measurement data related to the land and other land related surfaces and spaces, to include designing and devising the measurement specification and standards to accomplish these measurements with the desired precision and accuracy and error control and adjustment, including the use of all instrumentation applicable to such measurements typically being, but not limited to distances, heights, angles, directions, positions, areas, volumes, and other measurements associated with these quantities.

PROFESSIONAL SURVEYING:

The application of knowledge of the science of surveying measurement, the legal principles of boundary location, the laws related to boundaries and land use the applicable mathematical and computational theories and principles the nature and other forces which affect positional accuracy, the land planning and development concepts pertinent to sub division of land and property surrey.

LOGICAL SCOPE OF PROFESSIONAL SURVEYING:

Original surveys for the establishing property boundaries Retracement of property boundaries Field survey for topographical and other maps Photogram metric surveys for Topographical and other maps Construction of maps and other graphics for design and planning Layout and staking to guide construction. Measurement and plotting the position of constructed works Geodetic and other precise control surveys Surveys for mining and other subsurface operations Hydrographic and underwater survey Making survey and maps for land information systems Design of measurement of specification for various surveys Development of measurement standards for various survey Application, use and adjustment of measurement instrument. Development of relative geometric positional and other accuracy needs

for land information systems

TECHNIQUES:

The techniques used for surveying and land measurement are dependent upon the type of survey conducted. In this section there are two choices.

Types of survey Techniques

TYPES OF SURVEY:

A simple classification is:

Land Survey, which fix property lines, calculate land areas and assist with the transfer of real property from one owner to other

Engineering Survey, which collect the data needed to plan and design engineering projects. The information ensures the necessary position and dimension control on the site so that the structure is built in the proper place and as designed

Informational survey, obtain data concerning topography, drainage and manmade features of a large areas. This data is portrayed as maps and charts.

Another way to make a simple classification

Geodetic Survey are precise and over large areas require the curvature of the earth to be considered. Distances and angle measurement must be very accurate. A wide variety of techniques are used including triangulation, traversing, leveling and astronomical direction fixing.

Plane Surveys which is considered the surface of the earth to be plane. Curvature is ignored and calculations are performed using the formula of plane trigonometry and the properties of plane geometry. These may be considered accurate for limited areas.

TECHNIQUES:

Triangulation Trilateration Traverse Levelling Radiation

TRIANGULATION:

Triangulation consists of a series of connected triangles which adjoin or overlap each other, angles being measured from determined fixed stations. Triangulation reduces the number of measures that need to be taped and for this reason is often a preferred method of survey. A known base-line measurement is required. Three examples of triangulation systems are shown below.

A single chain of triangles is a rapid and economical system for covering a narrow strip of land. A chain quadrilaterals is more accurate with checks being made by various combinations of angles and sides as the survey proceeds. Larger areas use a central point arrangement. A point to note is that all

angles should be more than 20 . Angles less than 20 are not considered valid

for fixing position. They introduce inaccuracies. This is much the same in navigation where a fix by two bearings requires an angle of intersection os

approx 90 , and for three bearings approximately 60 . Angles less than 30 are

not acceptable.

TRILATERATION:

It uses electronic distance measuring equipment to directly measure the lengths of the sides of triangles from which the angles can be calculated. It is a very useful method for rough terrain where positions can be accurately carried forward and is seen as an alternative method to triangulation.

TRAVERSE:

A traverse consists of a series of lines, whose lengths and direction are measured, connecting points whose positions are to be determined. The route of the traverse line can be adjusted for obstacles such as rough or timbered terrain. A traverse may be either open or closed as shown.

An open traverse begins at a point of known position and ends at a station whose relative position in unknown. This type of traverse is frequently used for preliminary survey for highways. A closed traverse begins and ends at the same point whose position is known.

LEVELLING:

Leveling is the operation of determining the differences of elevation by measuring vertical distances directly on a graduated rod with the use of a leveling instrument such as a dumpy level, transit or theodolite. This method is called direct leveling or differential leveling. Indirect leveling can be done using the principle that differences in elevation are proportional to the differences in atmospheric pressure. The difference in elevation between two points can also be determined trigonometrically using vertical and horizontal or inclined distances.

Benchmarks are very important in leveling. They are permanent objects of known elevation located where there is least likehood of disturbance. They may be a metal or concrete post set to the ground, a notch in a tree root or a peg or spike in a tree.

RADIATION:

Radiation is a surveying technique often used in conjunction with a plane table. From a fixed position directly above the corresponding location on the ground bearings are taken to various points at the boundary of the survey area. The bearing lines are drawn on the paper on the table. Distance to the points are measured the converted to required scale on the sheet. Radiation surveying can be performed in a similar way directly on the ground taking bearings and distances from a fixed position and recording them for later work. Similarly plane table surveying may be used with the other techniques such as a traverse or triangulation.

S U R V E Y I N G U N I T S

STANDARD SURVEYING UNITS:

Acre - The acre is a unit of area equal to 43,560 sq ft, or 10 square chains or 160 square poles. It derives from a plowing area that is 4 poles wide and a furlong (40 poles) long. A square mile is 640 acres. The Scottish acre is 1.27 English acres. The Irish acre is 1.6 English acres.

Arpent - Unit of length and area used in France and Canada. As a unit of length approximately 191.8 feet. The arpent is a unit of area approximately .845 acres or 36,802 sq ft.

Chain- Imperial = Imperial = 4 poles = 22 yards. Attempt by Edmund Gunter to make land measure, a decimal system. His 66 foot chain had 100 links, but possibly variant by locale.

Circle- One revolution = 360

Degree- 60 nautical miles Foot- Imperial = 12 inches. Based on the length of the human feet. Engineers Chain- A 100 foot chain containing 100 links of one foot

apiece Furlong- Unit length equal to 40 poles (220) yards. Its name is derived

from “ furrow long “ the length of a furrow that oxen can plow before they are rested and turned

Hectare- Metric unit of area equal to 10000 sq m or 2.471 acres or 107,639 sq ft.

Inch- Imperial. From old English (ynce) meaning one twelfth. Link- Unit of length equal to 1/100 chain (7.92 inches) Mile- Imperial = 1760 yards = 8 furlongs from mile passum a term

used by the Roman armies of Caesar “mile” and “pace”. Nautical Mile- Used in marine and aeronautical navigation as 1nm = 1

(latitude)

Pole- Unit of length and area. Also known as a perch or rod. As a unit of length, equal to 16.5 feet. A mile is 320 poles. As a unit of area equal to square with sides one pole long. An acre is 160 square poles.

Yard- Imperial = 3 feet. From old English gerd or gried.

S U R V E Y I N G T E R M S

STANDARD SURVEYING TERMS:

Aliquot -The description of fractional section ownership used in the US public land states. A parcel is generally identified by its section, township and range.

Azimuth -The number of degrees from north that a line runs measured clockwise.

Benchmark - Survey mark made on a monument having a known location and elevation serving as a reference point for surveying

Call – Feature, land mark or measurement called out in a survey. Chain carrier- An assistant to the surveyor, the chain carriers

moved the surveying chain from one location to another under the direction of the surveyor. This was position of some responsibility and the chain carriers took an oath as “sworn chain carriers” that they would do their job properly.

Conditional Line-An agreed line between neighbors that has not been surveyed but not granted.

Corner- The beginning or end point of any survey line. The term corner does not imply the property was in any way square.

Declination-The difference between magnetic north and the geographic north. Surveyors used a compass to determine the direction of the survey lines. Compasses point to magnetic north rather than the true north.

Landmark- Survey mark made on a permanent feature of the land such as a tree, pile of stones etc.

Line Tree- Any tree that is on a property line, specifically one that is also a corner to another property.

Mete- A limit point or mark. To butt up against.

Metes and Bounds- An ancient surveying system that describes a parcel of land in terms of its relationship to natural features and adjacent parcels.

Merestone- A stone that marks a boundary. Monument-A permanently placed survey marker such as a stone

shaft sunk into the ground. Point of Beginning-The starting point of the survey. Plat-A drawing of a parcel of land. Range- In the US public land surveying systems a north – south

column of townships, identified as being east or west of a reference longitudinal meridian.

Searles Spiral- A surveying technique used by rail road surveyors in the late 1800s and early 1900s whereby they approximately a spiral by use of multiple curved segments.

Section- An area in a square mile. Strip-A rectangular piece of land adjoining a parcel, created

when a resurvey turns up a tiny bit larger than the original survey. The difference is accounted due to temperature or other effects on the measuring chain.

Tie line-A survey line that connects a point to other surveyed lines.