Astronomy Report

CIVIL ENGINEERING DEPARTMENT DIPLOMA GEOMATIK UKUR (DGU) ---------------------------------------------------------------------------------------------------------------------

DCG2063 FIELD ASTRONOMY ---------------------------------------------------------------------------------------------------------------------

REPORT: SOLAR OBSERVATION --------------------------------------------------------------------------------------------------------------------PREPARED BY : HAMIDZIE BIN OTHMAN ID NO. : 01DGU14F1022 CLASS : DGU2A

PREPARED FOR : PUAN SHARIFAH LAILATON KHADIJAH BINTI SYED ABDULLAH DATE OF SUBMISSION: 27 MARCH 2015

TABLE OF CONTENTS

Bil.

Contents

1.

Title of Practical Work

2.

Introduction

3.

Purpose / Objectives

4.

Equipment Used

5.

Procedure Works

6.

Result (Booking)

7.

Analysis / Data Computation

8.

Conclusions (Comment)

Page

SOLAR OBSERVAT ION REPORT

INTRODUCTION Azimuth determination from solar observations has been around and practiced by surveyors and navigators for centuries. While some technologies such as GPS have made azimuth determination from observing celestial bodies less common, others such as electronic theodolites with powerful onboard computers and timing devices have made solar and stellar observations more convenient and accurate. Although at this time no instrument manufacturer has an onboard solar ephemeris and reduction programs whereby the observer would point to a reference mark and the Sun/star and read the azimuth of the line instantly, the technology, however, is here now to achieve this. In the last 6 or 7 years the use of astronomical observations in surveying has seen a great come back. Once a common tool in land surveying, the growth of urban surveying over the years since the 1940's seemed to have caused a decline in the use of astronomy for azimuth determinations. In 1984, POB Magazine published an article entitled `Advantages of the Hour Angle Method for Sun Observations' by David R. Knowles. This article stirred some good feedback and debate, and has been followed up by numerous informative technical addendum. At about the same time, R. B. Buckner published his book titled A Manual on Astronomic and Grid Azimuth'. I believe that these publications and others helped revive interest and excitement about surveying astronomy. These publications provided surveyors with a thorough background, as well as instructions and techniques to determine accurate astronomic azimuth. They were also strong proponents of the hour angle method for solar observations. A side effect of some of these articles was the denigration of the value and accuracy of the traditional solar altitude method for azimuth. What I am trying to present here is a more moderate view and a defense of a place in your skills tool kit of the altitude method. Solar observation are necessary to determine datum for a Cadastral Survey. Apart

from that, it is used to determine the true bearing before starting the Cadastral Survey. It is necessary to check previous bearings in the Certified Plan. True Bearings are used when we want to re-fix the damaged or lost boundary stones.

PURPOSE / OBJECTIVE The purpose or objective of this practical activity are: a)

To expose students on how to compute an observation weather based on the star or sun in giving the bearing of the line which refers to true north.

b)

Able to apply the concept of solar observation in a true Cadastral Survey work.

c)

To understand on how to read the observations properly and accurately.

d)

To understand on how to book and compute the booking based on the step of the solar observation calculation given.

e)

To prepare student to get use to the situation on the real work.

f)

To understand on how read the “Almanac”.

EQUIPMENT

Tripod (1 units) EDM or Total Station (1unit) -to find the angle and measured the distance

-used as a platform for supporting the weight and maintaining the stability of the total station or the prism

Sun Filter (1 units)

-to protect the eyes from ultraviolet radiation (UV) and blue light which can cause several serious eye problem when observing the sun

FIELD WORK PROCEDURE

Figure 1a

Figure 1b

Figure 1c

Figure 1d

The field work involved in the determination of azimuth of a line from sun observation consists of following steps: 1. Carry out temporary adjustment of a theodolite at the observation station with face left condition. 2. Open the lower plate main screw and swing the telescope to bisect the reference object. Fix the lower plate main screw and bisect accurately using the lower plate tangent screw. Note down the horizontal circle reading. 3. Swing the telescope by opening the upper plate main screw. Bring the image of the sun into the upper left quadrant of the diaphragm (Figure 1a). Close the upper plate main screw and then bring the vertical hair tangent to right limb of the sun using the upper plate tangent screw. As soon as the lower limb of the sun makes contact with the horizontal hair, the chronometer time is recorded. Note down the horizontal (as well as vertical, if altitude of the sun is required to be observed) circle readings.

4. Next, bring the image of the sun into lower right quadrant using the upper and vertical plate tangent screws. The vertical hair is kept in tangent to left limb of the sun using by the upper plate tangent screw. As soon as the upper limb of the sun makes contact with the horizontal hair, the chronometer time is recorded (Figure 1b). Note down the horizontal (as well as vertical, if altitude of the sun is required to be observed) circle readings. 5. Open the upper plate main screw and swing back the telescope to the reference object. Close the upper plate main screw and bisect the reference object. Note down the horizontal circle reading. 6. Change the face left of the instrument into the face right condition and repeat step 2 with the instrument in face right condition. 7. Swing the telescope by opening the upper plate main screw. Bring the image of the sun into the upper right quadrant of the diaphragm (Figure 1c). Close the upper plate main screw and then bring the vertical hair tangent to left limb of the sun using the upper plate tangent screw. As soon as the lower limb of the sun makes contact with the horizontal hair, the chronometer time is recorded. Note down the horizontal (as well as vertical, if altitude of the sun is required to be observed) circle readings. 8. Next, bring the image of the sun into lower left quadrant using the upper and vertical plate tangent screws. The vertical hair is kept in tangent to right limb of the sun using the upper plate tangent screw. As soon as the upper limb of the sun makes contact with the horizontal hair, the chronometer time is recorded (Figure 1d). Note down the horizontal (as well as vertical, if altitude of the sun is required to be observed) circle readings. 9. Repeat step 5. Thus, a set of observation is to be taken. It consists of four instants of time and four horizontal circle readings (and four vertical circle readings). An azimuth of the line AZL should be computed for each pointing on the sun. For any field observation, it may consist of one or more sets, but a minimum of three sets is recommended.

RESULT (BOOKING)

ANALYSIS / DATA COMPUTATION A. COMPUTATION OF THE SOLAR OBSERVATION 1. As soon as the solar observation have been booked, a calculation of the solar observation in finding an azimuth must be compute right away. 2. Firstly, the average solar angle was calculated as below : Average horizontal solar angle =

Total horizontal angle 4

3. The result is then filled in Average horizontal solar angle row. 4. Next, step 2 was repeated the same way in finding the average altitude. Before that, for the vertical angle of the left face, 90 0 - θ and for the angle on the right face, θ - 2700. Then from there the average vertical angle can be find by using the step as below as Average vertical solar angle =

Total vertical angle

4 5. Then, from there to find the altitude, step below was used Corrected altitude = Average vertical solar angle - parallax and refraction *** The parallax and refraction (biasan dan bedalihat) are based on the reverse (back) of the solar observation Form. 6. Next, to find the RO horizontal average angle step below was used RO horizontal average angle =

Total RO horizontal angle 2

7. Then, the coordinate for the observation station was been done by using the step below. Original Coordinate N/S and E/W = given according location of the State Observation Station Coordinates N/S and E/W = obtained from the respective observation Station Latitude = Original Latitude - Difference x 0.0032 Original Latitude = given according location of the State

8. Then, to find the azimuth of the sun by using the step as below Declination = refer to the Star Almanac 57 Difference = 0h 16m x , 0h 25m x 3600

57 3600

Polar Distance, P = 900 + Declination (southern sun) or 900 - Declination (northern sun) Calculated Azimuth sun by using the formula below Cosine Azimuth =

cos P -(sin α x sin Φ) cos α x cos Φ

9. Not last but least, after the azimuth of the sun, the find the difference step below was used. Difference =Azimuth of sun - The Average to the sun 10. Next, from the difference, we can find by following the step below. Truth RO = Difference + RO horizontal average angle RO Grid bearing = Truth RO ± the misclose (tirusan) 11. Lastly, to find the average RO Grid Bearing step below was used RO Grid bearing =

deviation 1 + deviation 2 2

(Notes - please refer to the respective survey class)

B. OBSERVATION RULE 1.

Observation can be carried out either in the mornings or afternoon. The vertical angle observed must be between 15 - 30 exceptions to certain cases. Each solar observation requires 2 set observation and each sets consists 4 observations of the sun.

2.

The reference mark (RO) is taken from the back bearing. Readings are taken when the horizontal are cuts the sun through central point and the vertical axis coincides with tangent of the sun.

3.

Data of declination angle is referred to the Star Almanac for surveyor. For second class surveys the azimuth value between two sets of observations must not exceed 30 seconds and for first class survey must not exceed 10 seconds.

4.

Based on the solar observations, bearings are calculated and recorded in the solar observation form.

CONCLUSION / COMMENT First of all i would like to thank our astronomy lecturer, Pn Siti Kamisah for patiently teach us the CG206 that was astronomy. From this practical or field work activity, i have succeed in conducting this activity. It is because, i have fulfill most of the objective of this activity and there are: 1.

To expose students on how to compute an observation weather based on the star or sun in giving the bearing of the line which refers to true north.

2.

Able to apply the concept of solar observation in a true Cadastral Survey work.

3.

To understand on how to read the observations properly and accurately.

4.

To understand on how to book and compute the booking based on the step of the solar observation calculation given.

5.

To prepare student to get use to the situation on the real work.

6.

To understand on how read the “Almanac”. Throughout conducting the observation, the problems that been face during the

solar observation is that observation cannot be carried out perfectly due to bad weather such as cloudy, rainy or even haze. Beside that, the factor in finding the azimuth value between two sets of observations must not exceed the limits is due to the incorrect reading of the theodolite or EDM or even incorrect in centering the bubble of the equipment. From this activity i can say that, theres are quite a lot observation that been make throughout this semester. Between all the observed result, i managed to compute 2 closed observation with the limit does not exceed 10” and even 2 closed observations with the limit exceed 1’. As for the rest of the observations i managed to compute a second class survey.