MEASUREMENT OF HORIZONTAL DISTANCE Flashcards
is defined as the length of a step in walking. Note that 2 paces is equivalent to a stride.
Pace
consists of counting the number of steps, or paces, in a required distance.
Pacing
The length of an individual’s pace is done by walking with natural steps back and forth over a level course at least 100 m long and dividing the known distance by the average number of steps. The result is called
Pace Factor
The formula for pace factor
PF = Length of the line/number of paces
m/pace
Once the PF was established, the approximate length of a line can be determined by
multiplying the pace factor by the corresponding number of paces for that line.
Desirable relative precision:
1/200 or lower
is suitable in determining approximate distances in conditions where low precision is sufficient such as reconnaissance survey, small-scale mapping, and locating details.
Pacing
Factors Affecting Pace Factor
❑ Speed of pacing
❑ Roughness of the ground
❑ Weight of clothing and shoes
❑ Fatigue on the part of pacer
❑ Slope of the terrain
❑ Age and gender of individual
involves direct measurement of distances with steel tapes
Taping
most common way of measuring
taping
consists of stretching a calibrated tape between two points and reading the distance indicated on the tape
taping
Types of Measuring Tape
Steel tape
Metallic tape
Non-metallic tape
Invar tape
Fiberglass tape
Builder’s tape
Wire
Phosphor-Bronze tape
Nylon-Coated Steel tape
➢ Made of ribbon of steel
➢ 0.5 – 1.0 cm in width and weighs 1.5 kg per 30 meters
➢ Available length: 30m, 50m, and 100m
➢ Designed for most conventional measurements in surveying and engineering works.
Steel Tape
➢ Made of brass, copper, or stainless steel to increase its strength and reduce stretching
➢ Unsuitable for precise measurements and should not be used around electrical installations.
Metallic Tape
➢ Coated with plastic material
➢ Reduce effects of moisture, humidity and abrasion
➢ Safe to use when working around electrical installations
Non-Metallic Tape
➢ Made of an alloy of nickel (35%) and steel (65%)
➢ Very low coefficient of thermal expansion. Its name was derived from “invariable” since it is less affected by thermal stress
➢ Use for precise measurement
➢ 10 times expensive as ordinary steel tape
➢ Requires careful handling since it is easily bent and damaged
Invar Tape
➢ Woven with fiberglass (longitudinal and transverse pattern)
➢ Strong and flexible
➢ Best used in vicinity of electrical equipment
Fiberglass Tape
➢ Smaller cross sections and lighter than engineer’s tape
➢ Commonly used in building construction
Builder’s Tape
➢ Used before thin flat steel tapes
➢ Still practical in hydrographic survey
Wires
➢ Rust-proof tape
➢ Used in vicinity of salt water
Phosphor-Bronze Tape
➢ Flexible and crack-resistant
➢ Steel core tape
➢ With coating of permanently bonded non-conducting nylon
➢ Resistant to corrosion and rust
Nylon-Coated Steel Tape
Taping Accessories
Range Pole
Chaining Pins
Plumb Bob
Hand Level and Clinometer
Wooden Stake or Hub
➢ Made of wood or metal about 2 to 3 m long
➢ Painted with alternate 30 cm long red and white bands that can be used for rough measurements
➢ Used as a temporary signal to indicate the location of points, direction of lines, and alignment.
Range Pole
➢ Used to mark tape lengths
➢ About 30 cm in length and are made of number 12 steel wire, sharply pointed at one end, and have a round loop at the other end
➢ 1 set consists of 11 pins carried on a steel ring
Chaining Pins
➢ Used to project the tape end to the exact point on the ground
➢ Should be attached to a 1.5 m long string/cord
➢ Should weigh a minimum of 8 oz and have a fine point
Plumb Bob
➢ Consist of a metal sighting tube with a level bubble
➢ For approximate measurement of vertical angles
Hand Level and Clinometer
➢ Made of 5 cm × 5 cm × 30 cm wood for marking points or stations on the ground
➢ The top of the hub is usually marked by driving a nail or tack on its center
Wooden Stake or Hub
is a method of obtaining horizontal distances and differences in elevation based on the optical geometry of the instrument.
Tacheometry
The lens of the telescope of the instrument is equipped with __________ that are used to capture rod readings.
stadia hairs
based on the principle that in similar triangles, the corresponding sides are proportional
stadia method
The equipment for stadia measurements consist of
theodolite/transit and a graduated rod called stadia rod.
When a line is measured with tape that is “too long”, the corrections are applied to the observed length by ___________
adding
When a specified or required length is to be laid out with a tape that is “too long” , the corrections are to be ___________ from the known length to determine the corrected length to be laid out.
subtracted
When measuring or laying out lengths with tape that is “_______”, the
corrections are applied opposite to that stated in the first two rules
too short
