Modern Height Determination Techniques and Comparison of Accuracies

Abstract

In academic studies and engineering works, it is required to determine height differences between points or the height of points itself in those applications such as measurements of national or local networks, vertical applications of bridge, dam and infrastructures, maintenance and control measurements, determination of vertical crustal movements, motorway, railway, sewerage and pipe line measurements. Height determination can be classified as geometric levelling, trigonometric levelling and GPS/Levelling depending on used instruments or the methods applied. They have advantages and disadvantages. The purpose of this study is to analyze the trigonometric levelling with using total station, which are capable of high accuracy observing vertical angles and distances, geometric levelling with using digital level and GPS/Levelling with using GPS observations. To fulfill this aim, a levelling line with 11 points was established in Alaeddin Keykubat Campus area of Selçuk University. During the study done on this levelling line, three separate geometric levelling with different three equipments (Wild N3 precise level, invar rods, Sokkia B2 automatic level and wooden rods, Sokkia SDL 30M digital level and bar coded aluminum rods), trigonometric levelling by using different two equipments (Wild T2 theodolite for vertical angle measurements and Topcon GTS 701 electronic total station for distance measurements, only Topcon GTS 701 electronic total station for vertical angle and distance measurements) and GPS/levelling (with Leica 9500 receiver) were used. The height differences of precise levelling were assumed as true values, and these differences were then compared with these from other techniques and mean square errors were computed using these measurement differences. Consequently, it was seen that the results from digital level showed the best approach to those from precise geometric levelling.

Full text

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
1
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Modern Height Determination Techniques and Comparison of Accuracies
Ayhan CEYLAN, Cevat INAL and Ismail SANLIOGLU, Turkey
Key words: Levelling, GPS, Orthometric height, Accuracy
SUMMARY
In academic studies and engineering works, it is required to determine height differences
between points or the height of points itself in those applications such as measurements of
national or local networks, vertical applications of bridge, dam and infrastructures,
maintenance and control measurements, determination of vertical crustal movements,
motorway, railway, sewerage and pipe line measurements.
Height determination can be classified as geometric levelling, trigonometric levelling and
GPS/Levelling depending on used instruments or the methods applied. They have advantages
and disadvantages.
The purpose of this study is to analyze the trigonometric levelling with using total station,
which are capable of high accuracy observing vertical angles and distances, geometric
levelling with using digital level and GPS/Levelling with using GPS observations. To fulfill
this aim, a levelling line with 11 points was established in Alaeddin Keykubat Campus area
of Selçuk University. During the study done on this levelling line, three separate geometric
levelling with different three equipments (Wild N3 precise level, invar rods, Sokkia B2
automatic level and wooden rods, Sokkia SDL 30M digital level and bar coded aluminum
rods), trigonometric levelling by using different two equipments (Wild T2 theodolite for
vertical angle measurements and Topcon GTS 701 electronic total station for distance
measurements, only Topcon GTS 701 electronic total station for vertical angle and distance
measurements) and GPS/levelling (with Leica 9500 receiver) were used. The height
differences of precise levelling were assumed as true values, and these differences were then
compared with these from other techniques and mean square errors were computed using
these measurement differences. Consequently, it was seen that the results from digital level
showed the best approach to those from precise geometric levelling.

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
2
/
14
Modern Height Determination Techniques and Comparison of Accuracies
Ayhan CEYLAN, Cevat INAL and Ismail SANLIOGLU, Turkey
1. INTRODUCTION
Nowadays, not only in academic studies but also in engineering works it is run into problems
of determination of height differences between points or the height of points. For these
studies, it may be showed some examples, such as:
- Surveying of levelling networks
- Vertical applications, maintenance and control measurements of big structures like
bridge, dam, very tall buildings, and tower.
- Determination of vertical crustal movements
- Motorway, railway, sewer and pipeline measurements.
Instruments used in surveying and measurement method are determined in relation to
topography of land, target precision, and aim. In this study, accuracies of height
determination techniques have been compared with each other according to used instrument,
and measurement method.
2. DEFINITION AND ANALYSIS HEIGHT DETERMINATION TECHNIQUES
There are a lot of geodetic methods for determining of heights or height differences. These
methods are classified as geometric levelling, trigonometric levelling, and GPS/Levelling
according to used surveying instruments and applied measurement method. The historical
development of heights determination techniques is given in Figure 1.
2.1. Geometric Levelling
Geometric levelling is the determination of the height differences by using level and hold
vertical rods (Figure 2). Geometric levelling may firstly appear a method as a very simple and
yielding the best result method. However, the practical applications have shown that carrying
out of this method is very difficult on the rough ground and sensitive to regular or irregular
model errors. The preventative measures must be taken to eliminate or reduce model errors
stemmed from instrumental and outer surroundings. If it is not, these situations decrease the
survey velocity, thus the cost of surveying rises (Banger, 1981; Niemeier, 1986; Ceylan,
1988; Baykal, 1989).
The effects of such errors can be reduced by using Schwartz or Red pants methods or,
applying appropriate measurement methods, taking equal backward and forward observation
range, the round trip surveying, following BFFB (backward forward forward backward) or
FBBF (forward backward backward forward) observation order or surveying calibration in
lab and surveying additional parameters such as pressure, temperature and time at the survey
moment (Baykal, 1989).

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
3
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Figure 1. The historical development of heights determination techniques
Figure 2. The fundamental principal of geometric levelling (Pelzer, 1983)
Nowadays, also motorized geometric levelling applications have been done by establishing
survey hardware on the land vehicle, thus successful results have been obtained. According to
geometric levelling, the advantages of the motorized levelling may be summarized as below;
- Improve 40-60% in production velocity
- Decrease errors connected to time
- More observation ray, thus decreasing asymmetric refraction error
- More accuracy
Only disadvantage of this technique is that the cost of instrument and vehicles is very high
and level points must be on the edge of the road (Niemeier, 1986; Becker, 1986).

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
4
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2.2. Trigonometric Levelling
Height differences are computed by using vertical angle and distance in trigonometric
levelling. According to the land, time and observing vertical angle, trigonometric levelling
can be classified as follows:
- Unidirectional trigonometric levelling
- Leap-Frog (jumped) trigonometric levelling
- Reciprocal trigonometric levelling
With development of the electronic total stations which are able to observe vertical angle and
distance by high accuracy the trigonometric levelling has just updated again together, then
various studies have been made about this subject (Rueger and Brunner, 1982; Kuntz and
Schimitt, 1986; Aksoy, 1993; Erkaya, 1993; Ceylan, 1993; Ceylan, 1997; Kasser, 2002).
Applications of the motorized trigonometric levelling have been made by placing survey
hardware of the trigonometric levelling on the land vehicle. The motorized trigonometric
levelling is equal accuracy ( km/mm2
m
≤) and equal cost with the motorized geometric
levelling when the motorized trigonometric levelling is done according to following rules;
- The reciprocal and simultaneously vertical angle observations
- The reciprocal distance measurements
- The short observation ranges (∼250-300 m)
- Using calibrated instruments
- Carried out by the experienced person
More than 27% speed of production has been reached with motorized trigonometric levelling.
Therefore, the studies have shown that the motorized levelling may be alternative method to
geometric levelling (Whalen, 1985; Chrzanowski v.d., 1985; Chrzanowski, 1989; Becker,
1986; Uzel, 1991).
2.2.1. Survey and Computation Model in the Unidirectional Trigonometric Levelling
The observations of the unidirectional trigonometric levelling have been made by using total
station that is set up in a station point to vertically established target tablet as unidirectional
(Figure 3). ij
Z vertical angle and ij
S slope distance are measured. It is assumed that level
surfaces are same centered sphere surfaces in the survey model.
In figure 3,
'
ij
Z : vertical angle that must be measured
ij
Z: vertical angle that is observed
r
dZ : model error that is caused by refraction
ij
ε: model error that is caused by plumb line deviation
ij
S: slope distance
m
R : radius of the Earth spheroid

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
5
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Height difference between i
P and j
P points )h( ij
∆,
() ()()
ijrijijij
2
m
2
ij
ijijij Zsin.dZ.SZsin.
R2
S
Zcos.Sh +ε−








+=∆ (1)
is computed by equation (1). In this equation, first term is nominal height difference and
second term shows that radius of the Earth spheroid affects the height difference, third term
shows that vertical refraction and plumb line deviation affect the height difference. Because
ij
ε and r
dZ are not known in the application, third term has been neglected, thus the height
difference is computed by first two terms (Co
ş
kun, 1996).
Figure 3. Survey model of the unidirectional trigonometric levelling
2.2.2. Survey and Computation Model in the Reciprocal Trigonometric Levelling
The observations have been made reciprocally for each other in this trigonometric levelling
by using total station that is set up in the two stations point (Figure 4). ij
Z and ji
Z vertical
angles and ij
S slope distance are measured.
If equation (1) is used in observations that are made in every two points and if arithmetic
mean of height difference is computed,

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
6
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()
()
()
()
Zsin.dZ.SZsin.dZ.S
ZsinZsin
R2
S
ZcosZcos.S
2
1
h
ji
j
rjiijij
i
rijij
ji
2
ij
2
m
2
ij
jiijij
ij












+ε++ε
−−+−
=∆ (2)
equation (2) is obtained.
Figure 4. Survey model of the reciprocal trigonometric levelling
In equation (2), first term is nominal height difference and second term shows that radius of
the Earth spheroid affects the height difference, third term and fourth term show that vertical
refraction and plumb line deviation affect the height difference respectively. Because ij
ε and
r
dZ are not known in the application, third term and fourth term have been neglected, thus the
height difference is computed by equation (3) (Co
ş
kun, 2002).
()
()








−+−=∆ ji
2
ij
2
m
2
ij
jiijijij ZsinZsin
R2
S
ZcosZcos.S
2
1
h (3)

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
7
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14
2.2.3. Survey and Compute Model in the Leap-Frog (Jumped) Trigonometric Levelling
The observations have been made to target tablets of station points in this trigonometric
levelling by using total station that is set up in a point among the station points (Figure 5).
ki
Z and kj
Z vertical angles, ki
S and kj
S slope distances are measured.
Figure 5. Survey model of the Leap-Frog (jumped) trigonometric levelling
If equation (1) is used in observations in back-sight and fore-sight,
()
()
()
()
()
()
ki
i
rkikikj
j
rkjkj
ki
22
kikj
22
kj
m
kikikjkjij
Zsin.dZSZsin.dZS
Zsin.SZsin.S
R2
1
Zcos.SZcos.Sh
+ε++ε−
−+−=∆ (4)
equation (4) is obtained.
In equation (4), first term is nominal height difference and second term shows that radius of
the Earth spheroid affects the height difference, third term and fourth term show that vertical
refraction and plumb line deviation affect the height difference respectively. Because kj
ε,

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
8
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14
ki
εand i
r
dZ , j
r
dZ are not known in the application, third term and fourth term have been
neglected, thus the height difference is computed by equation (5) (Co
ş
kun, 1996).
()
()
ki
22
kikj
22
kj
m
kikikjkjij Zsin.SZsin.S
R2
1
Zcos.SZcos.Sh −+−=∆ (5)
2.3. GPS/ Levelling
GPS/Levelling is the most recent and advanced method that is used in the determination of
heights. Three-dimensional coordinates or coordinate differences can be obtained by GPS in
the geocentric Cartesian coordinate system. The Cartesian coordinates are transformed to
geodetic latitude, geodetic longitude, and ellipsoidal heights according to selected reference
ellipsoid, i.e. WGS84. The ellipsoidal heights obtained by GPS are not directly used for
practical surveying. The ellipsoidal height has to be transformed to orthometric height, which
is distance measured along the plumb line between the geoid and a point on the Earth’s
surface and taken positive upward from the geoid (National Geodetic Survey, 1986).
Relationship between ellipsoidal height and orthometric height is shown in figure 6.
Figure 6. Relationship between ellipsoidal height and orthometric height
Difference between ellipsoidal height and orthometric height is defined as geoid height or
geoid undulation. The fundamental equation among these concepts is written as follows
NHh += (6)
Here;
h: ellipsoidal height
H: orthometric height
N: geoid height (
İ
nal, 1996)

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
9
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Geoid heights of all points have to be computed before computing orthometric heights. The
geometric approach is carried out more common for computing geoid heights in the regional
studies. The mathematical surface is fitted by using the geoid heights of points whose
ellipsoidal heights and orthometric heights are known enough density in the geometric
approach. Then geoid heights of points whose ellipsoidal heights are known can be computed
by the assistance of this surface.
3. NUMERICAL APPLICATION
3.1. Definition of the Study Area and Area Surveys
A levelling line with 11 points that are 50m spaced on the same line, was established
throughout east-west direction in Alaeddin Keykubat Campus area of Selcuk University with
the aim of searching accuracies which are obtained by geometric levelling, trigonometric
levelling, GPS/levelling using the most recent and advanced technological equipments
(Figure 7). The measurements were performed independently from each other as
combinations with different equipments all the way through line. The fifty-five height
differences among points were computed (Table 1).
The different three equipments were used in geometric levelling. First equipment has one
Wild N3 precision level and two invar rods that are divided to two-party and three meter in
length. Second equipment has one Sokkia B2 automatic level and two wooden rods that are
three meters in length. Third equipment has one Sokkia SDL30 digital level and two bar
coded aluminum rod that is five meter in length. All rules that must be taken into
consideration were carried out carefully in the geometric levelling surveys.
The two different equipments were used in the trigonometric levelling. First equipment has
one Topcon GTS 701 electronic total station, Wild T2 theodolite, five prisms, and target
table. Second equipment has one Topcon GTS701 total station, five prisms, and target table.
In the trigonometric levelling with first equipment, the distances among the points were
measured by using Topcon GTS701 total station and the vertical angles were reciprocally
measured by using Wild T2 theodolite as four series. The heights of instrument, prisms, and
target tables were measured in mm level. Both distances and vertical angles were measured
by using Topcon GTS701 total station in the trigonometric levelling with the second
equipment.

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
10
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14
Figure 7. Levelling line
Five Leica GPS receiver and set were used in GPS surveys. The GPS surveys were realized
by using static method with 30 minutes sessions. GPS data were processed by SKI 2.3 GPS
software after downloading to computer. The ellipsoidal heights were obtained in conclusion
of the processing. Geoid heights were taken from study made beforehand at the same area
(Çorumluo
ğ
lu et al, 2002)
Table 1.The height differences (m)
Line
No Geometric Levelling Trigonometric Levelling GPS/
Levelling
I.Equipment II.Equipment III.Equipment I.Equipment II.Equipment
1-2 -2.2776 -2.2779 -2.2740 -2.2814 -2.2826 -2.2636
1-3 -3.9875 -3.9874 -3.9890 -3.9938 -4.0031 -3.9922
1-4 -5.6586 -5.6565 -5.6600 -5.6677 -5.6684 -5.6519
1-5 -7.3062 -7.3062 -7.3060 -7.3155 -7.3240 -7.3168
1-6 -9.0392 -9.0364 -9.0370 -9.0496 -9.0635 -9.0482
1-7 -10.7386 -10.7358 -10.7300 -10.7380 -10.7585 -10.7349
1-8 -12.5076 -12.5059 -12.5050 -12.5021 -12.5326 -12.5286
1-9 -14.1844 -14.1814 -14.1870 -14.1938 -14.1830 -14.2011
1-10 -15.7315 -15.7337 -15.7300 -15.7608 -15.7655 -15.7572
1-11 -17.0885 -17.0854 -17.0880 -17.1283 -17.0973 -17.1136
2-3 -1.7099 -1.7093 -1.7140 -1.7106 -1.7223 -1.7286
2-4 -3.3810 -3.3815 -3.3820 -3.3829 -3.3899 -3.3880
2-5 -5.0285 -5.0277 -5.0330 -5.0419 -5.0430 -5.0532
2-6 -6.7616 -6.7598 -6.7580 -6.7653 -6.7680 -6.7846

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
11
/
14
Line
No Geometric Levelling Trigonometric Levelling GPS/
Levelling
I.Equipment II.Equipment III.Equipment I.Equipment II.Equipment
2-7 -8.4610 -8.4567 -8.4600 -8.4670 -8.4735 -8.4713
2-8 -10.2299 -10.2270 -10.2320 -10.2251 -10.2510 -10.2650
2-9 -11.9068 -11.9044 -11.8990 -11.9102 -11.9305 -11.9375
2-10 -13.4539 -13.4515 -13.4520 -13.4790 -13.4960 -13.4936
2-11 -14.8109 -14.8089 -14.8100 -14.8450 -14.8185 -14.8500
3-4 -1.6712 -1.6689 -1.6690 -1.6757 -1.6704 -1.6597
3-5 -3.3187 -3.3188 -3.3210 -3.3217 -3.3127 -3.3246
3-6 -5.0517 -5.0501 -5.0450 -5.0535 -5.0579 -5.0560
3-7 -6.7511 -6.7463 -6.7510 -6.7547 -6.7568 -6.7427
3-8 -8.5201 -8.5159 -8.5210 -8.5182 -8.5405 -8.5364
3-9 -10.1969 -10.1955 -10.2000 -10.2008 -10.2010 -10.2089
3-10 -11.7440 -11.7416 -11.7400 -11.7696 -11.7740 -11.7650
3-11 -13.1010 -13.1019 -13.1050 -13.1364 -13.1109 -13.1214
4-5 -1.6475 -1.6474 -1.6480 -1.6527 -1.6553 -1.6649
4-6 -3.3806 -3.3782 -3.3790 -3.3798 -3.3854 -3.3960
4-7 -5.0800 -5.0792 -5.0780 -5.0748 -5.0819 -5.0830
4-8 -6.8489 -6.8475 -6.8520 -6.8478 -6.8660 -6.8767
4-9 -8.5258 -8.5265 -8.5300 -8.5277 -8.5340 -8.5492
4-10 -10.0728 -10.0722 -10.0720 -10.0856 -10.0957 -10.1053
4-11 -11.4299 -11.4311 -11.4200 -11.4565 -11.4285 -11.4617
5-6 -1.7330 -1.7322 -1.7330 -1.7235 -1.7395 -1.7314
5-7 -3.4324 -3.4304 -3.4280 -3.4184 -3.4360 -3.4181
5-8 -5.2014 -5.1999 -5.2020 -5.1971 -5.2133 -5.2118
5-9 -6.8783 -6.8764 -6.8800 -6.8701 -6.8852 -6.8843
5-10 -8.4253 -8.4216 -8.4200 -8.4405 -8.4378 -8.4404
5-11 -9.7823 -9.7776 -9.7730 -9.8055 -9.7909 -9.7968
6-7 -1.6994 -1.6979 -1.7000 -1.6951 -1.7042 -1.6867
6-8 -3.4683 -3.4688 -3.4680 -3.4712 -3.4855 -3.4804
6-9 -5.1452 -5.1434 -5.1430 -5.1485 -5.1584 -5.1529
6-10 -6.6923 -6.6921 -6.7020 -6.7213 -6.7085 -6.7090
6-11 -8.0493 -8.0489 -8.0500 -8.0753 -8.0548 -8.0654
7-8 -1.7690 -1.7690 -1.7680 -1.7738 -1.7791 -1.7937
7-9 -3.4458 -3.4456 -3.4440 -3.4502 -3.4513 -3.4662
7-10 -4.9929 -4.9936 -4.9940 -5.0177 -5.0079 -5.0223
7-11 -6.3499 -6.3512 -6.3470 -6.3789 -6.3468 -6.3787
8-9 -1.6766 -1.6766 -1.6770 -1.6820 -1.6865 -1.6725
8-10 -3.2239 -3.2231 -3.2190 -3.2473 -3.2335 -3.2286
8-11 -4.5809 -4.5799 -4.5790 -4.6120 -4.5710 -4.5850
9-10 -1.5470 -1.5471 -1.5450 -1.5674 -1.5535 -1.5561
9-11 -2.9041 -2.9045 -2.9030 -2.9305 -2.8958 -2.9125
10-11 -1.3570 -1.3576 -1.3580 -1.3606 -1.3375 -1.3564

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
12
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3.2. Processing of Surveys
The height differences of precise levelling were assumed as true values in computation of the
accuracies of measurements that were made by every one of the equipment. By means of ε
true errors, root mean square errors (RMSE) of height differences were computed as follows
(Table 2);
[]
n
mεε
=
m
(8)
Here, n is the number of measurements.
Table 2. The root mean square errors computed according to different measurement methods,
different equipments, and their measurement times.
Levelling
method Equipment RMSE (mm)
Total Time
(Hour)
SOKKIA B2 Automatic Level and Wooden Rods ±3.7 31
Geometric
Levelling SOKKIA SDL 30M Digital Level and Bar coded Rods ±2.0 18
WILD T2 Theodolite TOPCON GTS 701 Total Station
±16.4 25
Trigonometric
Levelling TOPCON GTS 701 Total Station ±14.7 17
GPS/ Levelling LEICA 9500 GPS receiver and set ±18.8 5
4. CONCLUSIONS
Not only horizontal positioning has to be determined but also heights of points have to be
determined in geodetic studies. The situation of the present instrument or equipment, cost,
production velocity, topographical structure of study area must be considered before
initialling survey procedures.
When table 3 and the results of the present written sources are investigated, questions of
which levelling method must be carried out and in which occupation may be answered as
follows:
- If there is a geoid information at levelling in rural area in which density of point is so low
and in which shadow area is not formed because of tree, etc., the GPS/levelling method
must be chosen. In the opposite situations, the geometric levelling method with digital
level or the trigonometric levelling method with total station may be chosen.
- It is appropriate to choose the geometric levelling with digital level or the trigonometric
levelling with total station at levelling in urban area or semi-urban area in which density
of point is so high
- If the deformation surveys are carried out in big structures as bridge, dam, GPS receivers
may be used for observations on condition that they are not far from the reference points.
In addition, the precision levelling method should be chosen by using digital level with
invar rods or optic-mechanic level in type of these deformation surveys.

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
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- In construction projects as highway, railway, smoothing area, the GPS/levelling, the
trigonometric levelling with total station, the geometric levelling with digital level, and
laser level may be chosen respectively.
REFERENCES
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Çorumluo
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Kasser, M., 2002. New Modern Height Determination Techniques, FIG XXII. International
Congress, Washington, D.C.USA, April 19-26

TS 33 – Vertical Reference Frame
Ayhan Ceylan, Cevat Inal and Ismail Sanlioglu
TS33.5 Modern Height Determination Techniques and Comparison of Accuracies
From Pharaohs to Geoinformatics
FIG Working Week 2005 and GSDI-8
Cairo, Egypt April 16-21, 2005
14
/
14
Kuntz, E., and Schmitt, G., 1986. Precise Height Determination by Simultaneous Zenith
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BIOGRAPHICAL NOTES
Dr. Ayhan CEYLAN is an assistant Professor at Selcuk University in Turkey. He has been
academic staff at the university since 1987. His research interests focus on high precision
surveying techniques, surveying applications, high precision levelling, mine surveying
applications, and height determining techniques.
Dr. Cevat
İ
NAL is a Professor at Selcuk University in Turkey. He has been academic staff at
the university since 1983. His research interests focus on high precision surveying
techniques, surveying applications, engineering surveying applications, geodetic networks
adjustment, high precision surveying instruments, and deformation studies.
Dr. Ismail SANLIOGLU is a research assistant at Selcuk University in Turkey. He has been
academic staff at the university since 1995. His research interests focus on GPS applications,
GPS data processing, commercial GPS processing softwares, using IGS products, geodetic
networks, and local geoid determining studies.
CONTACTS
Assist. Prof. Dr. Ayhan CEYLAN, Prof. Dr. Cevat INAL, Dr. Ismail SANLIOGLU
Selcuk University, Engineering and Architecture Faculty
Department of Geodesy and Photogrammetry Engineering
Alaaddin Keykubad Campus, Selcuklu
Konya
TURKEY
Tel. +90 332 2231923
Fax + 90 332 2410635
Email: aceylan@selcuk.edu.tr , cevat@selcuk.edu.tr , sanlioglu@selcuk.edu.tr
Web site: http://www.harita.selcuk.edu.tr/