SFP CH7 Flashcards
What is a traverse? What are the basic types?
A traverse consists of an interconnected series of lines
called courses, running between a series of points on the
ground called traverse stations.
The traverse types are open and closed.
Open Traverse- An open traverse neither forms a closed geometric figure nor does it end at a point of known position.
2 types of Closed Traverse- Loop and Connecting.
Loop Traverse- A loop traverse starts and ends at the same point, forming a closed geometric
figure called a polygon.
Connecting Traverse- looks like an open traverse,
except that it begins and ends at points (or lines) of
known position (and direction) at each end of the traverse (it can be checked mathematically for the error of closure and the relative accuracy of
the survey. Connecting traverses are generally used for horizontal control in route surveys.)
What is the purpose of a control survey?
The relative positions of all the
points are accurately determined in a control survey. (serve as fixed reference positions from
which other surveying measurements are made later on
to design and build the project.)
What is the purpose of witnessing a point? What are
the two basic methods?
This serves as an aid to
finding the point when it is covered with snow, leaves,
or soil, or as a means to replace it if the point is accidentally disturbed (as of activities)
2 basic methods:
wooden stakes and tied in
wooden stakes: (sometimes called straddle
hubs) may be set near the point, so that the intersection of two strings stretched between opposite pairs of hubs will mark the position of the station.
Tied in- a control station may be tied in,
by distance measurement, to nearby existing points that
can serve as witnesses.
List six factors regarding proper witnessing of a
point,
1.At least three witnesses should be used.
2.Witnesses should be permanent and readily visible
points, situated somewhat above the ground surface.
3.Witnesses should not be more than 100 ft (or 30 m)
from the control station.
4.The ties should be roughly at right angles to each
other,
5.Ties to trees (or poles) should be made to tacks or
nails marked with colored ribbon.
6.Distances of ties should be measured with an appropriate degree of accuracy, depending on the purpose
of the survey.
What is meant by adjusting a traverse?
This process of adjusting or
closing the traverse ensures that the station coordinates
will be as accurate as possible. Traverse adjustment is
also important for land or boundary surveys because
legal descriptions of property must have no geometric
inconsistencies.
List the basic steps for closing a traverse.
1.Compute the angular error and adjust the angles.
2.Compute course bearings or azimuths.
3 .Compute course latitudes and departures.
4.Determine the error of closure and accuracy; if unacceptable, then redo traverse or parts of traverse. If
acceptable, move to step 5
5.Adjust course latitudes and departures.
6.Compute station coordinates.
For geometric consistency, what should the sum of
the adjusted interior angles in a traverse with n sides
equal?
‘The sum of the interior angles in any loop traverse
must equal (n-2)(180°) for geometric consistency; n is
the number of angles (of sides) in the traverse.
Briefly define the terms latitude and departure as
they pertain to traverse computations.
Latitude : The latitude of a traverse course is simply the Y
component of the line in a rectangular XY coordinate
system (north-south)
Latitude = delta y = Lcosine Beta
Departure: The departure of a traverse course is simply the X component of the line in a rectangular XYcoordinate
system (east-west)
Departure: delta x =Lsin (Beta)
What is the sign convention for latitude and
departure?
Latitude: f the traverse course has a northerly (N) bearing, its latitude will have a positive sign
(+); a positive latitude is sometimes called the northing
of the line (see Figure 7-9). If the course has a southerly
(S) bearing, its latitude will carry a negative (—) sign; it
may also be called the southing of the line.
Departure: If a line has an easterly (E) bearing, its departure will
have a positive sign; a positive departure may be called.
the easting of the line. If the line has a
westerly (W) bearing, its departure will be negative; it
may be called the westing of the line.
In an adjusted traverse, what should the sum of latitudes or departures equal? Why?
The simplest are “approximate” procedures called the compass (or Bowditch) rule and the transit rule.
Because a loop traverse begins and ends at the
same point, the sum of the latitudes and the sum of
the departures should both be equal to zero.
What are the compass and transit rules used for?
Compass Rule: Corrections are applied to the latitudes and departures in proportion to
the lengths of each of the courses.
Transit Rule:
This rule is best used for traverse surveys in which the angles have been measured with greater
precision than the distances. It changes the latitudes and
departures in such a way that the lengths of the courses are
changed slightly, but the bearings remain almost the same.
A formula for the transit rule can be written as follows:
What is meant by the term inversing?
It is generally necessary to compute the new directions
and lengths of the traverse courses that result from the
adjustment of the traverse. The process is called inversing.
What is the trapezoidal rule used for?
method called the trapezoidal rule may then be used to
approximate the area between the traverse line and the
irregular boundary. The sum of the two areas represents
the total enclosed area of the property.
What is meant by the term side shot?
side
shot is simply an extra measurement of both distance
and direction to the point in question, from the traverse
station. The coordinates of the point can be computed
by adding the latitude and departure of the side shot to
the coordinates of the traverse station.
A distance-distance type of intersection problem
involves the measurement of an angle and/or distance from each of two stations of known position.
In this type of problem it is necessary fixed points, to know the distances from the two
Measurements A and B, to the new point, C; no angle are required
