7 - Azimuth by Solar Observation

Visayas Visayas State University College of Engineering DEPARTMENT DEPARTMENT OF GEODETIC ENGINEERING

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GEng 112 General Surveying II

Name: Name: ______ _________ _______ _______ ______ ______ _______ _______ ______ ___ Lab Schedu Schedule: le: ______ _________ ______ ______ _______ _______ _______ ____ Group Number: _________________________ 

Date Performe Performed: d: ______ _________ _______ ______  __  Date Submitte Submitted: d: ______ _________ ______ ______  ___ 

AZIMUTH BY SOLAR OBSERVA OBSERVATION Labra!ry Labra!ry E"er#i$e N% &

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In!r'u#!in .

Azimuth Azimuth determinations determinations are generally made by observing observing either either the sun or Polaris, although other stars may be used. The two methods for determining azimuth from the sun are the hour angle method and the altitude method. method. Accuracy Accuracy requirements requirements for the work, work, as well as accuracy of the data used in the calculations, will determine the method to be used. (Elgin, ichard !." II%

Ob(e#!ive)$*+ To determine the true direction (azimuth or bearing) of a line b a direct ob!er"ation on the !un.

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In$!ru,en!$ an an' A##e$$ e$$rie$+ Theodolite or #ngineer$! Tran!it% Peg! or &ub!% 'ange Pole!% and a piece of hite ard or Paper.

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-r#e'ure+ A% *. Prepar Preparati ation on Prior Prior to to Sighti Sighting ng the the Sun. Sun. a. Set up and and le"el le"el the the in!tr in!trume ument nt at one end end of a line line +ho! +ho!e e true true direc directio tion n i! to to be determined. b. Set the hori horizon zontal tal cir circle cle read reading ing to to zero% zero% and and ta,e ta,e a !ight !ight on a mar, mar, at at the the other  other  end of the line +ith the tele!cope in 'ire#! .$i!in. .$i!in . c. 'ele 'elea! a!e e the the uppe upperr clam clamp p then then%% rai! rai!e e and and poin pointt the the tel tele!co e!cope pe a! nearl nearl  a! po!!ible to+ard the !un +ithout loo,ing through the tele!cope. d. &old &old a +hite +hite card card from from - cm cm to * * cm behi behind nd the the eepie eepiece ce and and !lo+l !lo+l rotate rotate the the tele!cope both in azimuth and altitude. hen a circular !hado+ i! ca!t on the card clamp both motion!. e. 'ota 'otate te the the eepi eepiec ece e until until the the cro!! cro!! hair! hair! are are al!o al!o focu! focu!ed ed on the card card.. Then% Then% focu! the tele!cope and ma,e the image of the !un appear on the +hite card a! clearl and !harpl a! po!!ible. /. Sigh Sighti ting ng the the Sun Sun.. a. To ma,e ma,e the ob!e ob!er" r"at atio ion! n!%% the imag image e of the the !un ma ma be cente centere red d on the cro cro!! !! hair! or brought tangent to them. The fir!t method i! !impler to perform but the !econd method i! more accurate and +ill be u!ed in thi! particular e0erci!e. &alf  of the ob!er"ation! !hould be made +ith the !un in one 1uadrant and the other  half +ith the !un in the oppo!ite 1uadrant. b. Loo! Loo!en en the the upper upper moti motion on and and ta,e ta,e a !erie !erie! ! of !igh !ight! t! to to the !un !un fir! fir!tt +ith +ith the the tele!cope in 'ire#! .$i!in. .$i!in . c. 2oth 2oth "erti "ertical cal and and horizo horizonta ntall cro!! cro!! hair hair! ! are brou brought ght tang tangent ent to to the ea!t ea!tern ern lim limb b and the upper (for morning ob!er"ation) or lo+er (for afternoon ob!er"ation) limb

of the !un. The !e1uence! of image! ob!er"ed b thi! method are a! !ho+n in the accompaning !,etche! !ho+n belo+.

3igure *. Sighting the !un. d.

e.

f.

g.

h.

3or afternoon ob!er"ation! the horizontal cro!! hair i! !ighted a !hort di!tance abo"e the lo+er limb of the !un. Due to the !un$! apparent mo"ement in it! orbit the horizontal cro!! hair approache! tangenc. The "ertical cro!! hair !hould be ,ept continuou!l on the !un$! ea!tern limb b mean! of the upper tangent !cre+. The motion of the tele!cope i! !topped at the in!tant +hen the horizontal and "ertical cro!! hair! are !imultaneou!l tangent to the !un$! di!, a! !ho+n on the +hite card. 4l!o% the time i! ob!er"ed and the "ertical and horizontal circle! read. 5a,e a !econd ob!er"ation +ith the !un in the oppo!ite 1uadrant. The "ertical cro!! hair i! !et a !hort di!tance to the right of the !un$! +e!tern limb. The horizontal cro!! hair i! ,ept continuou!l on the !un$! upper limb b mean! o f the "ertical tangent !cre+. hen the horizontal and "ertical cro!! hair! are !imultaneou!l tangent to the !un$! di!, the "ertical and horizontal circle! are read. The abo"e ob!er"ation! are repeated +ith the tele!cope in the re"er!ed po!ition to obtain another !et of mea!urement. Since the reading! on the "ertical and horizontal circle! are ob!er"ed in oppo!ite 1uadrant! the a"erage "alue! +ill actuall repre!ent mea!urement! to the center of the !un$! di!,. hen the ob!er"ation! are completed% the tele!cope (no+ in re"er!ed po!ition) i! again !ighted along the line and the circle reading i! ob!er"ed for chec,ing purpo!e!. The horizontal circle reading !hould no+ read *6 degree!.

7. 'ecord the time% horizontal circle reading!% and "ertical circle reading! for each ob!er"ation made. 'efer to the accompaning !ample format for the tabulation of  ob!er"ed field data. P89NT9NGS 8N T&# SN T#L#S8P# P8S9T98N Direct

&8'9;8NT4L 4NGL# (loc,+i!e from mar, to the !un)