(Gm08v – LF) Page 1 of 10
NTNU
Geomatics
Exam:
TBA4230 GEOMATICS
Date: 11.12.2008 Time: 0900 – 1300
Solution, version 28.11.2010
Question no 1: GPS mm
1.1
Measuring methods using GPS
In this question it is meant from the teacher to answer shorttimestatic in (a) (ev other static
methods) to establish a local base point, to be able to use real time measurements in question (b)
where the local base station in (a) is used. Alternatively can another base station in a commercial
base station network also be used, for instance SATREF (The Norwegian Mapping Authorities)
or SPIDER (Leica), then just 1 own receiver is necessary. Using such alternative methods it is
not necessary to establish an own local base station (T on the figure). Therefore a suggestion of
using SATREF both in (a) and in (b) will be a bit illogical.
(a)
 Which measuring method using GPS do you recommend to
use to determine the coordinates and height of this local base
point T?
 Describe this method and explain why you recommend this
particular method.
Shorttimestatic method. Baseline measurements,
measuring time 515 min, post processing. Etc
Make your own assumptions and draw a figure showing the
GPS measurements you are planning to do to determine the new
base point.
3 known control points with good coordinates. 4 is also Ok, but with 4 it will actually be
too many measurements (find an optimal measuring plane, there also time is a factor).
Measuring baselines from these 3 points to point T. Eventually also measure between the
known control points to be able to check out the given coordinates.
(b)
Describe a method for the settingout that will be an effective way of settingout detail points in
real time with a quality (standard deviation) close to 1 cm.
Describe also the instruments that are needed to perform this settingout.
Realtimemeasurements (RTK, realtimekinematic). 1 receiver in the base station T, 1
rover receiver in the other end of the baseline(s). The rover is mounted on a steady held
rod. Transmittance of the corrections from the base via cell phone (or VHS, as there are
short distances).
1.2
Settingout
(a) Setting out plan, coordinate calculations.
Calculate the bearing from A to B.
Calculate the coordinates of the corner C, assuming an angle of 100 gons in the corner B
and the distance BC is 12.000 m.
From the coordinates:
T
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Δ
x
=
Δ
N
Δ
y
=
Δ
E
Plane bearing from
the calculator
Correction to the
correct quadrant
Plane
bearing
Distance
D
kp
AB
54.300
47.281
45.6081
200 154.3919
71.9999
The corner C, check also the figure:
Bearing AB
154.3919
Turning the bearing
+200.0000
Bearing BA
354.3919
Horizontal angle in B
100.0000
Bearing BC
54.3919
Distance in the map
projection plane
12.000
Δ
N
7.8802
N =
7056893.8762
Δ
E
9.0500
E =
499953.4220
(b)
Why must all three terms (EUREF89, UTM, zone 32) be given to get unambiguous coordinates
of a point?
Datum EUREF89 to give the datum…osv
UTM to show the map projection plane. UTM can be used in many datums, therefore a set of
UTM coordinate values has no meaning if the used datum is not given.
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 Fall '11
 Arnfinn
 Standard Deviation, Orders of magnitude, Geographic coordinate system, Coordinate system, Gm08v LF

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