Measurement of the horizontal control framework closed polygon method as a basis for making maps on the UNS Pabelan Campus

Mapping is a method of determining the location and position of an area on the earth’s surface, which includes measuring distances, angles, vertical directions, and horizontal directions. A situation map is the starting point for a project that aims to determine changes in the state of an area over time. The initial measurement of the scenario map takes the form of determining the points of the basic mapping framework that are evenly dispersed in the area being assessed by measuring the horizontal control frame. ents, was used in the horizontal control framework’s experimental procedure. The closed polygon approach was used to take measurements with 44 control points as a horizontal frame. The angle correction, abscissa correction, and ordinate correction satisfied the practicality to be employed, according to the data obtained from the measurement of the horizontal control frame using the closed polygon method. The implications of utilizing the closed polygon method to measure the horizontal control frame are the foundation for precise mapping of the situation for future measurements.


Introduction
Land surveying is a branch of geodesy that focuses on how to measure on the surface of the earth as well as below it in order to identify the relative or absolute position of points on the ground surface for purposes such as mapping and determining the relative position of an area [1] [2] [3].Surveying is a methodology or method for establishing one's relative position on the earth's surface in terms of distances, angles, and both vertical and horizontal directions.The general understanding of land measurement, according to its development, is a science that investigates techniques of gathering and processing measurement data about items on the earth's surface and its environs in order to determine their location or position [1] [4] [5].
One of the outcomes of land surveying is a map.Maps are essentially depictions of locations in which information is presented in the form of symbols.The map's functions include displaying an area's location on the earth's surface, explaining the form and distribution of various symptoms on the earth's surface, and defining an area's physical and social [1] [6].
A situation map is one of the large-scale results of the process of land measuring and topographic mapping of the earth's surface.For detailed mapping, a situation map measurement is a measurement used to create a map that may depict field circumstances, including both horizontal (x, y coordinates) IOP Publishing doi:10.1088/1755-1315/1314/1/012099 2 and height or elevation (z) positions.The situation map serves as the basis for activities in a particular job and to find out changes in the state of an area within a certain period of time.
Start of land surveying carried out in the situation mapping work is the creation of basic mapping points.The basic framework is a number of points whose coordinates are known in a particular system that has a function as a binder and a new size controller.Given its function, the basic frame points must be placed evenly throughout the area to be mapped with a certain density.Also considering that measurements for mapping take a long time, the base frame points must be planted strong enough and made of durable materials.In the measurement for making maps, there are two basic types of mapping (control) frameworks, namely horizontal (X, Y) and vertical (Z) as a determinant of the coordinates and control points of a building or a land for which a situation map and details will be made.In practice, the basic frame points, both horizontal and vertical, are made into one point [7] [8].
The UNS Pabelan campus is the UNS campus majoring in vocational engineering education and is the fifth branch campus of UNS located at Jalan Ahmad Yani Makamhaji, Kartasura, Sukoharjo Regency, Central Java 57161 just east of the UNS Hospital.Land Measurement UNS Pabelan Campus is included in closed land which does not yet have an accurate and detailed situation map.So it is necessary to create an accurate horizontal control framework using closed polygon method as the basis of mapping for UNS Pabelan Campus.

Methods
This research was carried out in stages in the period January 2022 -June 2022 which included the stages of preparation, benchmarking, soil surveying and data analysis as well as the description of the Horizontal Control framework.
This study uses an experimental method where the experiment used is direct land surveying on a closed land, the closed land is the UNS Pabelan Campus which does not yet have an accurate situation map.The flow of the method can be explained in the following chart.

Figure. 1. Research Method Chart
By looking at the chart above, it can be explained as follows [9], 1) Before carrying out surveying, it is better to prepare any tools and materials used in surveying so that the research runs smoothly.These preparations include: a) Borrowing measuring tools b) Preparation of tools and materials c) Making stakes d) Total Station function check e) Checking the function of other tools 2) After the preparation is complete, the next step is field orientation.Field orientation is carried out before taking measurements.This activity is carried out to determine the field conditions to be mapped so as to facilitate the determination of the position of the control points that will be used for measurement.The orientation of the field is in the form of benchmarks.
The tools used for benchmarking are roll meter, yalon and compass to facilitate sketching of the horizontal control framework used for measurement [10] [11], In addition, the installation of stakes and sketching of the distribution of control points were also carried out during field orientation.Determination of the basic point of horizontal (control) mapping has several criteria, namely: a) Between 3 adjacent points visible to each other.
b) The maximum distance between control points or stakes is 20 meters.c) The position of the point is safe and does not disturb the surrounding environment.d) Can include all locations that will be mapped by the next researcher.

Figure. 2. Bencmarking Sketch Illustration
3).After the preparation and benchmarking have been completed, a benchmarking sketch or a temporary horizontal control framework (Figure .2) is generated which will be used for the continuation of the research.The surveying technique used by the researcher is direct measurement.The direct measurement steps are as follows [12] [13] [14]: a) Install the Total Station measuring instrument above the stative established at point P1 (Fig. 2) as the station.b) Orient the Total Station with a skein or with an optical flashlight in such a way that it approaches directly above point P1 (Fig. 2).c) Set the bubble nivo box or tube to the center (leveling).d) Set up the prism above the last point or in the example sketch is point P40 (Fig. 2), then aim at the prism and set 0 degrees at a horizontal angle at point P40 (Fig. 2).Record the measured distance reading value into the measurement data form.e) Move the prism to point P2 (Fig. 2).then aim for the prism at point P2 (Fig. 2), then record the value of the horizontal angle readings and the measured distance into the measurement data form.f) To find the initial azimuth angle, set the Total Station horizontal angle to 0 to the north and aim for the P2 point (Fig. 2).record the horizontal angle which is the initial azimuth angle of measurement to calculate the next azimuth angle g) Perform steps (a) to (e) at all control points that have been pegged.

Data Analysis
The data from the survey work will then be analyzed using the closed polygon measurement method, which is described as follows [15]: 1) A closed polygon has a closed shape (kring) so that it forms a polygon or n (n is the number of points of the polygon).The geometric conditions for a closed polygon are: a) Terms of measure angle ∑ = ( − 2) .180° (1) ∑ = ( + 2).180° (2) Equation (1) for calculations using interior angles.Equation (2) for calculations using exterior angles.b) Terms of abscissa and ordinate ∑   = 0 (3) ∑   = 0 (4) 2) Geometrically, perfectly bound closed and open polygons have polygon angle closure requirements which can be explained that the sum of the measured angles is equal to the difference between the final direction angle and the initial direction angle plus a multiple of one hundred and eighty.In addition, it must meet the requirements of the abscissa (ΔX) and ordinate (ΔY).
The abscissa and ordinate requirements can be explained that the number of abscissa must be equal to the difference between the abscissa of the end point and the abscissa of the starting point of the polygon and the number of ordinates must be equal between the ordinate of the end point and the ordinate of the starting point of the polygon [3] [16].Error tolerance is the limit of the size of the error from the measurement results that can still be accepted.In polygon calculations, there are 2 (two) types of tolerances, respectively: a) Angular error tolerance (fβ), which is the limit of the amount of error that can still be accepted from the number of angle measurements with the requirements for the number of angles (see No. 1) [4] recommends corner covering tolerances as follows:  ≤  (5) With: K = the smallest scale of the angle reading on the measuring instrument n = quantity of control points The angle closure error (fβ) is divided equally among the angles.But there are times when fβ is not divisible by the number of angles.Then the angle correction that is different from the correction that has been rounded is given to the angle of the polygon which has the shortest legs of the angle, because the angle measurement with the short legs is not accurate due to the large shadow of the points of the short legs so that the aiming line is directed to the center of the image.what looks big becomes difficult and inaccurate [3] [17].
So the terms of the angle measure become: ∑ = ( − 2).180° +  (6) ∑ = ( + 2).180°+  (7) Equation ( 6) for calculations using inner angle Equation (7) for calculations using outer angle b) linear distance (fL), which is the limit of the amount of error that can still be accepted from the comparison: With : TL = linear accuracy ∑d.sinα = 0 + fx ; fx is correction of ∑d sin α ∑d.cosα = 0 + fy ; fy is correction of ∑d cos α ∑D = sum of polygon distance Then the linear distance cover error tolerance must be: 3) Polygon calculation steps: a) Calculate the angle measured by the polygon using the terms of the measure angle (eq. 1 and eq.2 ).b) Compare the result of the angle with the permissible angle error tolerance (eq.5).
• If angle errors is fβ ≤ K √n , then the calculation continues.
• If angle errors is fβ > K √n , then the calculation is stopped (then check for possible gross errors, miscalculations, wrong notes or copying, and so on, find possible gross errors during measurement, wrong targeting, wrong notes, and so on and consult with the supervisor) c) If fβ ≤ K √n : • Correct the error to all angles(fβ/n); n is quantity of control points • If fβ is positive, the correction is negative and the opposite.d) Start from the first azimuth that result of land surveying, calculate every azimuth with the formulas: Azimuth = previous Azimuth + outer angle -180° (11) or Azimuth = previous Azimuth + outer angle -180° -360° (12) or Azimuth = previous Azimuth + outer angle -180° + 360° (13) notes: the use of equation ( 11), (12) or ( 13) depending on the geometric shape of the measurement that can be known from the sketch e) Calculate : • d.sinα = distance x sinus of Azimuth every control point • d.cosα = distance x cosinnus of Azimuth every control point f).Add up all the distances (D), d sin and d cos from all sides of the polygon.The result of the sum (eq. 2 dan eq.7) • ∑d sin α = 0 + fx ; fx is correction of ∑dsin α • ∑d cos α = 0 + fy ; fy is correction of ∑d cos α. g) Calculate fL and TL, compare TL with specified linear distance cover fault tolerance: • If TL ≤ fL , then the calculation continues.
• If TL > fL, then the calculation is stopped (then check for possible gross errors, miscalculations, wrong notes or copying, and so on, find possible gross errors during measurement, wrong targeting, wrong notes, and so on and consult with the supervisor) h) Calculate the coordinates of each point (X,Y), Starting from the coordinates of the starting point, add algebraically, both for X and Y to get the coordinates of the previous point, with the formula: • X = previous X + di sin α; for the next point, X is the previous X.
• Y = previous Y + di cos α; for the next point, Y is the previous Y i) The errors of the abscissa (fx) and the ordinate (fy) are divided by the distance between the sides of the polygon on the abscissa x and the y ordinate [3].The rules for smoothing the abscissa and ordinate errors can be arranged in a mathematical equation, as follows:   (14)   (15) with : fxi = abscissa correction on the i-th polygon side fyi = ordinate correction on the i-th polygon side Di = length of side of polygon i The principle of calculating the definitive coordinates (x, y) of polygon points, in general can be formulated (Muhamadi, 2004), as follows: Xi = abscissa at point of i Xi-1 = abscissa at point of i -1 Yi = ordinate at point of i Yi-1 = ordinate at point of i -1 α'i = corrected azimuth at point -i

Results and Discussion
The Measurement of the Horizontal Control Framework at the UNS Pabelan Campus produces 44 control points P1 to P44 which are tied to the BM point of the UNS Pabelan Campus which is south of building A, UNS Pabelan Campus.The coordinates of BM X (475121,658), Y (9164403,678) were obtained from previous measurements using the GPS method with the Geodetic GPS tool RTK CHCNAV i50 in 2018.the measurements were made in collaboration with PT.ASABA.
In this measurement, the researcher uses a Total Station tool with an angle accuracy of 5 seconds, so for the angle error tolerance (fβ) in the Horizontal Control Framework measurement, it is Tolerance fβ = K √n Tolerance fβ = 5 seconds √44 Tolerance fβ = 33,1662 seconds So the angular error in this measurement should not be more than 33,1662 seconds, if it exceeds then you have to re-measure.From the measurement results of the Horizontal Control Framework, it can be seen whether the resulting angle correction meets the angle error tolerance according to the closed polygon method.The total number of outer angles measured is 8279,0194°, while the calculation of the outer angles that should be used for the measurement of 44 control points is as follows: outer Angle Calculation = (n+2)180° outer Angle Calculation = (44+2)180° outer Angle Calculation = 8280° So the angular error generated in this measurement is fβ = Outer Angle Calculation -Sum of Outer Angles fβ = 0,9805 degree fβ = 3530 seconds Since the angular error tolerance for this measurement is 33.1662 seconds, it means that the angular correction in this measurement exceeds the existing angular error tolerance fβ > K √n, so a remeasurement must be carried out.The researcher observes which points must be re-measured so that there are no more errors in measurement.After doing the re-measurement, the researcher recalculated the number of external angles which were calculated in this re-measurement resulting in 8279,9972°.
Then it is necessary to recalculate the angle correction with the re-measurement data so as to produce: fβ = Calculation of outer Angles -Sum of outer Angles fβ = 0,0028 degrees fβ = 9,9999 seconds So the angle correction for this re-measurement is 9.9999 seconds, with an angle error tolerance of 33,1662 seconds, so that fβ < K n, then proceed to the calculation of the correction to each control point, namely fβ/n where n is the number of control points.Then the angle correction of each point is 0,2273 seconds.After being corrected, proceed to the Azimuth calculation, by knowing the azimuth of point P1 which is 292,0125°, it can be seen the azimuth of each control point with the formula in the equation (11) (12) (13).After finding the azimuth of each control point, the next step is to calculate the coordinates (x,y) the results are as follows: From the results above, the coordinates at the starting point P1 and the end P1 are different, therefore there is an abscissa correction (fx) of 1,1031 meters and an ordinate correction (fy) of 0,2023 meters.With these results can be generated: TL = 0,0014 fl = 1,1215 So TL < fl, then the distance cover error is met and the definitive (X,Y) coordinates can be calculated, so that the final result of this measurement is the definitive (X,Y) coordinates as follows:

Conclusions
This research produces 44 control points as a horizontal framework using the closed polygon method.Stating that the resulting horizontal control framework meets the requirements of angle correction, abscissa correction, ordinate correction so that this horizontal control framework can be said to be accurate or can be used for further research, namely the measurement of the mapping of the UNS Pabelan Campus.

Table 1 .
Coordinate Calculation Results Before Correction

Table 2 .
Definitive Coordinate Calculation ResultsAfter obtaining the definitive (X, Y) coordinates from this measurement, the researcher continued to create a horizontal control frame drawing based on existing and accurate data using the AutoCAD application.