CC BY
1
УДК 528.421
Ruziev A., PhD on geographical sciences
senior lecturer Alfraganus University
TOPOGRAPHICAL SURVEYING USING SATELLITE MEASUREMENTS AND ASSESSMENT OF PLAN ACCURACY
Abstract. The purpose of the research is to study the methodology and accuracy of large-scale topographic survey based on experimental tests. For this purpose, a typical plot of land was selected for the test. Topographic survey on a scale of1:500 was carried out using satellite measurements, processed the results and created a digital terrain model. Control measurements were carried out on the plan and on the ground to assess the accuracy of the planned position of the points of the solid contours of the terrain depicted on the plans.
Keywords: GPS receiver, topographic survey, RTK, error, accuracy, DOP.
Introduction. With the continuous growth of the world population, the need for the construction of residential buildings, cultural, domestic, industrial and transport facilities is increasing. To address these issues, the United Nations 2030 Sustainable Development Agenda defines the objectives of "Ensuring openness, safety and environmental sustainability of cities and towns" [6].
The purpose of the research is to study the methodology and accuracy of large-scale topographic survey based on experimental tests. For this purpose, a typical plot of land was selected for the test, on which the following works was carried out: (i) topographic surveys at a scale of 1:500 using satellite measurements, (ii) processing the results, and (iii) creating a digital terrain model; (iv) carrying out control measurements on the plan and on the ground to assess the accuracy of the planned position of the points of solid contours of the terrain depicted on the plans, and the accuracy of the relief image.
Methods. Field measurements, probability theory, mathematical statistics methods were used in the research.
Used instruments. The engineering-topographic survey of the plot of land was carried out using the Stonex S900T GPS receiver. Detailed information about the technical characteristics of the tool can be obtained from [7]. The base GPS Stonex S900T (S902131800713) fixed on the roof of UZGASHKLITI's Tashkent branch building served as the initial reference point for GPS measurements, and GPS Stonex S900T (S902131800700) receivers served as the rover.
Measurements. Before surveying the situation and terrain, the technical feasibility of satellite measurements was studied. Part of the object is an open area where measurements can be taken. The rest of the area is occupied by tall trees and buildings and does not allow for observations. The antenna height was
"Экономика и социум" №4(119)-1 2024
www.iupr.ru
483
measured using a tape measure, its value was entered through the controller. Particular attention has been paid to the DOP value to ensure accuracy.
After the connection between the receiver and the base station was established, the mobile receiver was placed at characteristic points (pickets) of the area, similar to traditional surveying. The distance between pickets was taken within the values specified in the standard [4] depending on the scale of the survey. GPS measurements were carried out in accordance with the requirements of the relevant regulatory documents [2, 3].
At the experimental site, GPS measurements in RTK mode were completed with observations at a known point. After completing the GPS survey, the measurement results were loaded into the AutoCAD program and a digital topographic plan of the experimental site was created.
For the purpose of assessing the accuracy of engineering-topographic plans, solid contour points were marked on the topographic plan of the tacheometric survey and the length of the segments between them was determined by scale and the lengths of the same lines were measured on the ground (Table 1). The differences module ASi were calculated as follows [5]
ASi=SPii-Sgii, (1)
where Sp i and Sg i are, respectively, the horizontal distances between the contour points measured on the plan and on the ground.
Table 1.
Distances between contour points measured on the plan and on the ground
and their difference
Measured Differences ASi, cm Measured Differences ASi, cm
No. distance S, m AS? No. distance S, m AS?2
on the plan on the ground on the plan on the ground
1 7.411 7.438 -2.7 7.29 21 18.951 18.96 -0.9 0.81
2 33.052 33.085 -3.3 10.89 22 23.382 23.36 2.2 4.84
3 22.232 22.249 -1.7 2.89 23 43.747 43.783 -3.6 12.96
4 23.489 23.473 1.6 2.56 24 45.478 45.473 0.5 0.25
5 21.907 21.891 1.6 2.56 25 31.156 31.196 -4 16
6 37.352 37.441 -8.9 79.21 26 21.613 21.593 2 4
7 8.897 8.906 -0.9 0.81 27 16.407 16.393 1.4 1.96
8 50.57 50.598 -2.8 7.84 28 15.334 15.318 1.6 2.56
9 32.119 32.129 -1 1 29 30.510 30.525 -1.5 2.25
10 34.655 34.689 -3.4 11.56 30 55.204 55.219 -1.5 2.25
11 21.08 21.065 1.5 2.25 31 58.603 58.653 -5 25
12 53.053 53.125 -7.2 51.84 32 50.547 50.502 4.5 20.25
13 56.682 56.66 2.2 4.84 33 58.851 58.956 -10.5 110.25
14 51.515 51.521 -0.6 0.36 34 35.897 35.904 -0.7 0.49
15 46.079 46.042 3.7 13.69 35 36.371 36.344 2.7 7.29
16 20.11 20.07 4 16 36 29.886 29.820 6.6 43.56
17 39.076 39.122 -4.6 21.16 37 36.906 36.802 10.4 108.16
18 35.577 35.608 -3.1 9.61 38 50.977 50.896 8.1 65.61
'^KOHOMHKa h ^HyMM №4(119)-1 2024
www.iupr.ru
484
19 33.754 33.767 -1.3 1.69 39 55.007 54.935 7.2 51.84
20 33.397 33.369 2.8 7.84 40 26.058 26.104 -4.6 21.16
Z -24.1 255.89 14.9 501.49
Using the data in Table 1, the root-mean-square error of the differences (true error) and a single measurement was found from the following formula
mAS = ^[AS2]/n, (2)
where n is the number of lines measured on the plan and on the ground. The normal distribution law is characterized by the distribution density of the random variable A [1]
1 (A-a)2
<p(A)=—=e- 2o2 . (3)
The main parameters of a normally distributed random variable A in expression (3) a = M(A) and a2 = D(A) are found by the following formulas
a = M(A) = [A]/n, (4)
a(A) = ^D(A) « m = ^[A2]/n. (5)
Results. According to the table 1, mAS = ±4,35 cm were determined using formula (2). To confirm the reliability of this conclusion, the normal distribution of the series of differences found as a result of double measurements was checked using the laws of mathematical statistics.
Empirical values for constructing a normal distribution curve <p(A) were calculated using formulas (4) and (5): a = -0,23 cm; m = +4,35 cm.
The study of the distribution of a statistical series begins with the construction of a histogram. Based on the obtained data, an empirical distribution graph (histogram) was created (Fig. 1). The theoretical curve (Fig. 1) that smooths the histogram was built using the values calculated from the formula (3).
Figure 1. Histogram and theoretical curve
'^KOHOMHKa h ^HyM" №4(119)-1 2024
www.iupr.ru
485
To assess the degree of approximation of the statistical distribution (histogram) to the theoretical normal distribution law (distribution curve), K.Pearson's x2 value was used as a measure of their difference (Table 1).
According to the number of degrees of freedom r = 10 (k is the number of interval, s is the number of parameters) and x2 = 5,655 values obtained from the formula (6), the probability value p(x2) = 0,8416 was obtained from [1].
Discussions. The root-mean-square error of the image on the plan of GPS-survey in RTK mode of the contours ms = ±4,35 cm, which is two times more accurate than the standard value of ±10 cm, set for a scale of 1:500. Based on Pearson's x2 criterion, the probability of proportionality of empirical and theoretical distributions was p = 0,842. The fact that 0,842 >0,1 confirms that the series of errors obeys the law of normal distribution.
1. Большаков В.Д., Маркузе Ю.И. Практикум по теории математической обработки геодезических измерений. - М: Недра, 1984. - 352 с.
2. ГКИНП (ОНТА)-02-262-02. Инструкция по развитию съёмочного обоснования и съёмке ситуации и рельефа с применением глобальных навигационных спутниковых систем ГЛОНАСС И GPS. М., ЦНИИГАиК, 2002. - 70 с.
3. ГККИНП - 17-079-05 «Инструкция по развитию съёмочного обоснования и съёмке ситуации и рельефа с применением глобальных навигационных спутниковых систем ГЛОНАСС и GPS». Т., НЦГК, 2005. - 69 с.
4. ГККИНП 02-067-03 «Инструкция по топографической съёмке в масштабах 1:5000, 1:2000, 1:1000, 1:500». Т., НЦГК, 2003. - 199 с.
5. Неумывакин Ю.К. Практическое руководство по геодезии для архитектурной службы района. Москва: Недра, 1979. - 168 с.
6. The Sustainable Development Goals// https://www.un.org/sustainabledevelopment/cities/
7. User Manual for Stonex S900T GNSS Receiver. 2018/ https://www.top-sys.de/app/download/15331708124/S900T_User_Manual [ENG].pdf?t=1548665568
(6)
References:
"Экономика и социум" №4(119)-1 2024
www.iupr.ru
486
