S.H.H.S Building Construction. Surveying or land surveying is the technique, profession, and science...

S.H.H.S Building Construction

Surveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them. These points are usually on the surface of the Earth, and they are often used to establish land maps and boundaries for ownership or governmental purposes.

Number one (1) rule of Surveying:Incorrect Data is worse then no data!

1. Decision Making – selecting method, equipment and desired final point locations.

2. Fieldwork & Data Collection – making measurements and recording data in the field.

3. Computing & Data Processing – preparing calculations based upon the recorded data to determine locations in a useable form.

4. Mapping or Data Representation – plotting data to produce a map, plat, or chart in the proper form.

5. Stakeout – locating and establishing monuments or stakes in the proper locations in the field.

1. Plane Surveying – surveying with the reference base for fieldwork and computations are assumed to be a flat horizontal surface.

Generally within a 12 mile radius the pull of gravity is very nearly parallel to that at any other point within the radius and thus horizontal lines can be considered straight.

2. Geodetic Surveying – surveying technique to determine relative positions of widely spaced points, lengths, and directions which require the consideration of the size and shape of the earth. (Takes the earth’s curvature into account.)

1. Photogrammetry – mapping utilizing data obtained by camera or other sensors carried in airplanes or satellites.

2. Boundary Surveying – establishing property corners, boundaries, and areas of land parcels.

3. Control Surveying – establish a network of horizontal and vertical monuments that serve as a reference framework for other survey projects.

4. Engineering Surveying – providing points and elevations for the building Civil Engineering projects.

5. Topographic Surveying – collecting data and preparing maps showing the locations of natural man-made features and elevations of points o the ground for multiple uses.

6. Route Surveys – topographic and other surveys for long – narrow projects associated with Civil Engineering projects.

Highways, railroads, pipelines, and transmission lines.

7. Hydrographic Surveying – mapping of shorelines and the bottom of bodies of water.

Also known as bathymetric surveying.

Datum - This is an arbitrary level surface to which the heights of all points are referred. This may be the National Datum or local datum point established on a construction site.

Datum shifts can be very large. In one case, that of the Tokyo Datum and the commonly used World Geodetic System 1984 (WGS84) the difference is measured in kilometers or miles.

Mean sea level (MSL) is the average (mean) height of the sea between High and Low tides

Reduced Level (RL) – A distance recorded as a Height Above or Below the DATUM. This height is in feet.

MeanSea Level(MSL)

In this case the DATUM isMean Sea Level

RL 27.969

RL 44.695

MeanSea Level(MSL)

In this case the DATUM is lidof Pit

RL 4.420

RL 21.146

A benchmark (BM)in every-day language is a point of reference for a measurement. In surveying a benchmark is specifically any permanent marker placed by a surveyor with a precisely known vertical elevation (but not necessarily a precisely known horizontal location). Designed to be used for many projects.

A benchmark is physical structure with a known or assumed elevation.

To be considered a benchmark the point should be identified by a permanent or semi-permanent structure that will not be affected by frost heave, traffic vibrations or environmental changes.

Surveying standards have very specific guidelines on the required structure for benchmarks.

MeanSea Level(MSL)

In this case the DATUM is MSLBenchmark is Top of Pit

RL 27.969

RL 44.695

A Temporary benchmark (TBM) Benchmark usually placed for a particular project. Not designed to be a reference for other projects or for long term use

MeanSea Level(MSL)

In this case the DATUM is MSLBenchmark is Top of Pit

RL 27.969

RL 44.695

The historical method for measuring distance is the surveying chain.One of the first

chains used in the U.S. was the Gunter’s chain.

The Gunter’s chain was a series of links attached to a handle which included an adjustment for wear.

The chain was 22 yards (66 ft) long.

Modern chains are metal strips 100 feet long.

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Steel chain on holder

1. Hold holder vertical in the left hand.

2. Attach 100 foot end of the tape with the numbers up.

3. Wind tape up rotating the handle clockwise.

4. Remember to wipe tape with a dry cloth as it is wound onto the handle.

To rewind chain on holder:

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Odometer Wheel

Odometer wheels use different units on the odometers.

Insure you know the measuring units before you start to use the wheel.

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Range finder

Range finders are used to measure distance.

Two primary types are optical and EDM.

Optical range finders use lenses, mirrors and principles trig to determine distance.

OPTICAL RANGE FINDER

EDM = Electronic distance measuring

Many different models.

Many different features.

Many different prices. (Precision)

The staff is simply a large ruler, available in lengths of 3, 4 or 5 metres and usually made of aluminium with telescopic sections

Reading an E-type levelling staff

Read value atthehorizontalcross hair

The value is ?

1.9001.9101.9201.930

1.93

2

•It is important to hold staff plumb

•Use slow rocking technique

•Use vertical line in level to keep plumb

Rocking the rod should be used when a rod level is not available.

Set up the instrument where the benchmark can be viewed within correct parameters and a reasonable number of sights can be viewed. This location is identified as L1 circled in red

Definitions: 1- Backsight ( BS ): The first reading taken at every instrument station .

2- Foresight ( FS ): The last reading taken at every instrument station .

3- Intermediate sight ( IS ): Any reading taken at an instrument station between BS & FS

4- Turning point ( TP ): A point at which both BS & FS are taken before moving the staff

General Procedure:

The main purpose is to provide RL for a large number of points, such as the center line

of highway, or an area to produce a contour plan, this will be illustrated through the

following example of production longitudinal section (profile ) of a road.

A contour: is an imaginary line connecting points on the ground that have the

same elevation.

Contour Interval ( CI ): The vertical distance or elevation difference between two

successive contours.

Contour interval = 20m

1- Closely contours represent a steep slope, but spaced far contours represent a flat slope.

2- Contours of different values do not cross each other except in a cave, nor do they merge except in a vertically standing surface such as a wall.

3- A single contour can not split into two contours of the same value, and must be a closed circuit not necessary in limits of the contour plan.

4- Irregular contours represent a rough and uneven terrain.

5- contours are perpendicular to the direction of the steepest slope.

6- A hill or depression are represented by closed lines.

Factors affecting choice of contour intervals:

1- Contour plan scale: The larger scale is the smaller contour interval.

2- The importance and purpose of a contour plan : for more details, a small contour interval is used.

3- Accuracy, time and cost : For higher accuracy, a smaller interval is used.

4- The topography of the ground : For steep ground a large contour interval is used, but for flat ground a small contour interval is used.

5- The area covered by the plan: For larger areas, a large contour interval is used.