LESSON 2 Flashcards
GEODETIC
- The earth surface is considered as a ____ surface
- The line formed by joining any two points are considered as ____ –
as the same angles are spherical angles - The curvature of the earth’s surface is ____
- Involves ____ areas more than about 260 km^2
- Uses more precise instruments and modern technology like ____
- CURVED
- ARCH
- INCLUDED
- LARGER
- GPS
PLANE
- The earth surface is considered as a ____ surface
- The line formed by any two points are considered as a ____ – as the same angles are plain angles
- Plane surveying effect of the curvature of the earth’s surface is
____ - Involves ____ areas less than about 260 km^2
- Plane surveying uses normal instrument like a ____, etc
- PLAIN
- STRAIGHT LINE
- IGNORED
- SMALLER
- CHAIN MEASURING TAPE THEODOLITE
- In a right triangle, the square of the hypotenuse is equal to the sum
of the squares of the other two sides. - C^2 = A^2 + B^2
Pythagorean Theorem
____ is the most common angular units being employed.
Sexagesimal System
All ____ are simply ratios of one side of a right
triangle to a second side of the same triangle, or one side over
another side. The distinction between functions is which two sides
are compared in the ratio
Trigonometric Functions
MOST COMMON SURVEY EQUIPMENTS
- Theodolite
- Measuring Tape
- Total Station
- 3D scanners
- GPS/GNSS
- Level and rod
Most survey instruments are attached onto a ____ when in use. ____ or
digital tape measures are often used for measurement of smaller distances.
Tripod
Analog
- The ____ is
1/80th of a mile or 66
feet long. It is composed of 100 links,
with a link being 0.66 feet or 7.92 inches
long. Each link is a steel rod bent into a
tight loop on each end and connected to the
next link with a small steel ring
Gaunter’s Chain
Starting in the early
1900’s
surveyors
started using steep tapes to measure distances. These devices are still
called “chains” to this day
Gaunter’s Chain
A telescope that can be moved on both the horizontal and vertical
axes to align with a measuring stake (stadia)
Theodolite
An optical instrument, or a telescope, with a built-in spirit level
mounted on a tripod
Transit
Special form of theodolite that has a stadia diaphragm and an
anallatic lens. This eliminates the need for a chain because the
distance can be calculated using the diaphragm. This method has
been almost completely replaced by using a total station.
Tacheometer
This is a theodolite with an electronic distance measuring system
(EDM). With the EDM equipment, the distances can be measured
without a chain. This can allow a single surveyor to capture much
more information in a faster timeframe.
Total Station
A plane passing through a point on the surface of the earth and
containing the earth’s axis of rotation defines the astronomical or
true meridian at that point
Astronomical or True
- A ____ meridian lies parallel with the magnetic lines of force of
the earth. The earth acts very much like a bar magnet with a north
magnetic pole located considerably south of the north pole defined
by the earth’s rotational axis. - Ang risk ani is naga change siya so like ang loc sa point nimo nak
ani imo gigamit na reference is pwede ma change.
Magnetic
- In plane survey, it is convenient to perform the work in a rectangular
XY coordinate system in which one central meridian coincides with
a true meridian. - All remaining meridians are parallel to this central true meridian.
This eliminates the need to calculate the convergence of meridians
when determining positions of points in the system. The method of
plane surveying, assume that all measurements are projected to a
horizontal plane and that all meridians are parallel straight lines.
These are known as ____. The Oregon coordinate System
is a grid system.
Grid
- Grid Meridians
An arbitrary direction assigned to some line in the surface from
which all other lines are referenced. This could be a line between
two property monuments, the centerline of a tangent piece of a
roadway, or even the line between two points set for that purpose.
The important point to remember about assumed meridians is that
they have no relationship to any other meridian and thus the survey
cannot be readily (if at all) related to other surveys
Assumed
An angle less than 90° within a quadrant defined by the cardinal
directions.
Bearing
An angle between 0° and 360° measured clockwise from North
Azimuth
- The difference between the true value and the measured value of a
quantity - A deviation of an observation or a calculation from the true value
- Results of sources that cannot be avoided
- Its effect cannot be eliminated but minimized by careful work and
applying corrections
ERRORS
ERRORS
To be minimized, surveyor must have deep understanding on the
following;
(4)
o Kinds of Errors
o Sources of Errors
o Magnitude of Errors
o Effect of field measurements
- Inaccuracies in measurement caused by surveyor’s carelessness,
inattention, poor judgement and improper execution - May be caused by misunderstanding, inexperience or indifference
of surveyors - If in large scale, mistake is referred to as BLUNDER
- Not classified as error since magnitude of discrepancy from true
value is usually larger than of errors - Can be corrected only if discovered; mistakes must be avoided
MISTAKES
- Reading the wrong graduation of tape
- Incorrect recording of field notes
- Can be detected and removed from recorded measurements
MISTAKES
- Thermal expansion of Tapes
- Measurement made by using 30-m tape which is 5cm short
- Its effect can be minimized but cannot be eliminated
- Inconsistent pull of tape men on the ends of the tape
ERRORS
