distance measuring. two principles of measuring distance 1) it takes two points to form a line. 2)...

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Distance Measuring

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Page 1: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Distance Measuring

Page 2: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Two principles of measuring distance

1) It takes two points to form a

line.

2) The shortest distance between

two points is a straight line.

Page 3: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Distance

In surveying, the term “distance” has two uses.

The common use is to measure the displacement (distance) between two or more

points.

Distance can also be used to define the dimensions of an object

Page 4: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Best method

Determined by: Environment Use of the data Equipment available Expertise of individuals

Personal preference Topography Client specifications Regulations Standard practice

The most important factor is the use of the data.

Page 5: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Example

What method should be used to determine the amount of materials needed to build a fence?

Page 6: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Barbed Wire

Barbed wire is usually purchased in rolls that contain 100 rods of wire.

Does the precision need to be 1/100’s of a foot?

No

Page 7: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Wooden Pole

Horizontal poles are usually six to eight feet.

Is pacing an acceptable method?

Yes

Page 8: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Foundation

Measuring the location of forms for a foundation is a different job.

Distances should be measured to 1/8 or 1/4 inch.

Page 9: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Horizontal & Slope Distance

Horizontal distance is a distance measured on a horizontal plane. Horizontal distance can also be calculated.

Slope distance is a distance measured on a surface that is not a plane. For general surveying the difference between horizontal and slope distance is

ignored for slopes less than 5%.

Page 10: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Difference Between Horizontal and Slope Distance

The illustration shows the difference that occurs for a 3% slope. The actual difference in length is:

% Slope =riserun

100x

Rise =% slope

100 x run = 0.03 100x = 3

a2 = b2 + c2

b = a2 −c2

= 100 2 −32

= 99.95When the slope is 3%, the difference between slope distance and horizontal distance is 0.05 feet per 100 feet.

Page 11: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Horizontal Distance

To measure horizontal distance, the tape must be on a horizontal plane.

The earth surface is seldom a horizontal plane.

Page 12: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Slope distance

When distance is measured on the surface of the ground it is called slope (surface) distance.

Page 13: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Determining Horizontal Distance

The surveyor has two choices. Use equipment and techniques to measure horizontal

distance. Measure slope distance and collect additional information

to calculate horizontal distance.

Page 14: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Using Equipment To Measure Horizontal Distance

Chain, level and plumb bob.

Page 15: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Using Equipment To Measure Horizontal Distance--Stadia

Stadia distance is a horizontal distance because a level instrument is used to collect the data.

Page 16: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

1/2 Stadia

Page 17: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Using Equipment To Measure Horizontal Distance--(EDM)

An EDM measures distance by determining the amount of time required for a signal to leave the instrument, reflect off of the target, or object, and return.

If the instrument is level when the measurement is taken, the measurement is horizontal distance.

Page 18: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Calculating Horizontal Distance

To calculate horizontal distance you must know the slope distance and one additional bit of information for each station. Either: % slope

or Change in elevation

or Vertical angle.

Page 19: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Calculating Horizontal Distance --Percent slope

% Slope =RiseRun

100x

Rise =% Slope x Run

100

=2 255.30 x ft

100= 5.11 ft

a2 = b2 + c2

b = a2 −c2

= 255.30 2 −5.11 2 = 255.25 ft

Page 20: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Calculating Horizontal Distance--Difference in Elevation

a2 = b2 + c2

b = a2 −c2

= 234.5 2 −6.5 2 = 234.41 ft

Page 21: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Cosin θ =adjhyp

adj = Cosin θ x hyp

= 19.2 510.17 Cosin x ft

= 0.9444 510.17x

= 481.79 ft

Calculating Horizontal Distance--Vertical Angle

Page 22: Distance Measuring. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight

Questions ?