Download - Horizontal Positioning Methods
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HORIZONTALPOSITIONING
METHODS#4th week#
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he Geometry of Making Surveys
A survey network isa group of surveypoints all inter-connected such that
they are all in acommon coordinatesystem.
Triangulation
Triangulation is a type of surveying that uses the
principles of trigonometry to determine positions on thesurface of the Earth (i.e., latitude and longitude). If the
three angles of a triangle and the length of one side of
the triangle are known, the lengths of the other two
sides of the triangle can be computed.
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he Geometry of Making Surveys
Trilateration
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he Geometry of Making Surveys
Traverse A traverse is a series
of survey points, often
laid out in
approximately a
straight line.
A traverse starts from two known points to provide
position and aimuth (direction) for the survey and
ends on two known points to check the position andaimuth at the end of the survey. !he angles at each
point are measured and the distances between
ad"acent points are measured. !he observations can
then be used to compute the positions (latitude and
longitude) of each of the survey points along the line.
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he Geometry of Making Surveys
Intersection re#uires
the measurement of
angles by setting up
the theodolite at
control stations andtaking angle
readings by sighting
to the unknown
point(s).
A
B
P = Unknown Point
α
β
Intersection
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he Geometry of Making Surveys
Resection
In this method, the
theodolite is set up
over the unknown
point and angle
readings taken to atleast three control
points. $ecause the
theodolite is only set
up once, it is
considered to give a
less secure fix fromthe point of view of
checks and accuracy.
A B
!
P = "nknownoint
α β
$% $&
'
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TRAVERSE
Open Traverse Closed Traverse
!raverse networks have many advantages of
other systems,
including% &ess reconnaissance and organiation
needed
'hile in other systems, which may re#uire
the survey to be performed along a
rigid polygon shape, the traverse can change
to any shape and thus can
accommodate a great deal of different terrains
nly a few observations need to be taken
at each station, whereas in other surveynetworks a great deal of angular and linear
observations need to be made and
considered
!raverse networks are free of the strength
of figure considerations that happen in
triangular systems
cale error does not add up as the traverse
as performed. Aimuth swing errors
can also be reduced by increasing thedistance between stations
!raverse is a method in the field of surveying to establish control networks. It is also used in geodetic work.
!raverse networks involved placing the survey stations along a line or path of travel, and then using thepreviously surveyed points as a base for observing the next point.
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OPEN TRAVERSE
An open traverse starts at
a point of known or
assumed horiontal
position with respect to a
horiontal datum, and
terminates at an unknownhoriontal position. !hus,
open traverses end
without closure. pen
traverses are used on
route surveys, but should
be avoided whenever
possible since they
cannot be properly
checked. *easurements
in open traverses should
be repeated to minimize
mistakes.
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Closed Traverse
A closed traverse is
called starts at a
known or assumed
horiontal position
and terminates at that
point (i.e., loop
traverse), or it starts
at a known horiontal
position and
terminates at another
known horizontal position (i.e.,
connecting
traverses). $oth the
measured
angles and lengths in
a closed traverse maybe checked.
Loop Traverse
LinkTraverse
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Traverse Puroses
!raverse surveys are made for many
purposes to include%
+. !o determine the positions of exiting
boundary markers.
. !o establish the positions of boundary
lines.-. !o determine the area encompassed
within a boundary.
. !o determine the positions of arbitrary
points from which data may be obtained
for preparing various types of maps (i.e.,
establish control for map making).
/. !o establish ground control for
photographic mapping.
0. !o establish control for gathering data
regarding earthwork #uantities in railroad
highway, utility, and other construction
work.
1. !o establish control for locating railroads,highways, and other construction work.
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Traverse Prin!ile
*ust be considered%
+) !he data must be known before (minimum
re#uirements) control points or
+ control point and initial aimuth) !he data must be measured
2istance 3oriontal angle Initial aimuth if it isn4t known before
-) !he data must be computed
Initial aimuth (from control points) 5ext point aimuth 6oordinate point which should be sought7$ 8 7 A 9 d A$sin(: A$)
;$ 8 ; A 9 d A$cos(: A$)
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The data must "e kno#n "efore
6ontrol points can be obtained by
+. !he computation result from previous
measurements eg. >?, traverse,
triangulation, trilateration, resection,
intersection, etc. Assumed yourself locally eg. (@,@), (+@@,+@@)
but only + initial control point
Initial aimuth can be obtained by previous
measurement (data before)
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The data must "e measured
Initial aimuth can be measured by compass 2istance (length of traverse sides) can be
measured by roll meter, theodolite, !, E2* Angle between traverse sides can be
measured by theodolite, !, sextan, compass
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The data must "e !omuted
7$ 8 7 A 9 d A$sin(: A$)
;$ 8 ; A 9 d A$cos(: A$)
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Transitional Page
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