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 Labra!ry Labra!ry E"er#i$e N% &
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In!r'u#!in .
Azimuth Azimuth determinations determinations are generally made by observing observing either either the sun or Polaris, although other stars may be used. The two methods for determining azimuth from the sun are the hour angle method and the altitude method. method. Accuracy Accuracy requirements requirements for the work, work, as well as accuracy of the data used in the calculations, will determine the method to be used. (Elgin, ichard !." II%
Ob(e#!ive)$*+ To determine the true direction (azimuth or bearing) of a line b a direct ob!er"ation on the !un.
III%
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#! .$i!in. .$i!in . 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 eepie eepiece 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 eepi eepiec 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#! .$i!in. .$i!in . 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 accompaning !,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$! di!,. hen the ob!er"ation! are completed% the tele!cope (no+ in re"er!ed po!ition) i! again !ighted along the line and the circle reading i! ob!er"ed for chec,ing purpo!e!. The horizontal circle reading !hould no+ read *6 degree!.
7. 'ecord the time% horizontal circle reading!% and "ertical circle reading! for each ob!er"ation made. 'efer to the accompaning !ample format for the tabulation of ob!er"ed field data. P89NT9NGS 8N T&# SN T#L#S8P# P8S9T98N Direct
&8'9;8NT4L 4NGL# (loc,+i!e from mar, to the !un)
<#'T94L 4NGL#
T95# (Start)
'e"er!ed
Direct
(#nd)
B% /OM-UTATIONS+ *. Prior to the !tart of the ob!er"ation the follo+ing data mu!t be ,no+n in order to determine the true direction of the line: a. 5agnetic azimuth from !tation to mar, b. Latitude of the place of ob!er"ation c. Temperature during the ob!er"ation d. #le"ation of the place of ob!er"ation e. 5eridian of the place of ob!er"ation f. Date of the ob!er"ation
/.
Different "alue! needed for further computation! +ill ha"e to be referred to from the follo+ing table! and publication!: a. 'efraction and Sun$! Paralla0 b. 5ultiplier! for 8b!er"ed 2arometric Pre!!ure or ele"ation c. 5ultiplier! for Temperature d. urrent Solar #phemeri!
7.
The follo+ing "alue! +ill ha"e to be determined: a. 5ean horizontal angle from the mar, to !un b. 5ean "ertical angle to !un c. 5ean time at place of ob!er"ation d. GT +hen ob!er"ation +a! made e. Sun$! apparent declination on date and time of ob!er"ation f. True altitude of !un corrected for refraction and paralla0 g. 4zimuth of the !un h. True bearing of the line i. 5agnetic declination at the place of ob!er"ation
=.
The azimuth of the !un ma be computed from the follo+ing e1uation: o! ; > Sin d ? Sin h Sin 9 o! h o! 9
here ; i! the true azimuth of the !un% mea!ured from north cloc,+i!e in the morning and countercloc,+i!e on the afternoon. 4ngle ; ma be greater than @A. 4 minu! "alue of o! ; indicate! a "alue of ; greater than @A. The latitude of the ob!er"er$! po!ition i! *% h i! the true altitude of the !un% and d i! the !un$! apparent declination during the in!tant of ob!er"ation. The horizontal angle bet+een the bac,!ight and the po!ition of the !un (repre!ented b the mean of the horizontal angle!) i! u!ed +ith the azimuth of the !un to obtain the true bearing or azimuth of the line. -. 4n illu!trati"e !olar ob!er"ation problem i! gi"en a! an e0ample for the !tudent to under!tand and learn the mechanic! behind the re1uired computation!. SOLAR OBSERVATION% Gi"en the follo+ing data for !ighting! made on the !un: latitude of place ob!er"ation% N*BA7.*$C temperature during ob!er"ation% /*.*AC ele"ation of place of ob!er"ation% *-6.B/ mC meridian of the place of ob!er"ation% */A# longitudeC date of ob!er"ation% *6 4pril *@.
TELES/O-E -OSITION Tele$#.e 4ire#! Tele$#.e Rever$e'
-OINTINGS ON THE SUN HORIZONTAL ANGLE VERTI/AL ANGLE )#l#0i$e r, ,ar0 ! !3e )Mea$ure' Al!i!u'e $un* $un* 1&56 77%89 786 55%89 1&56 5:%59 786 <8%59 1&;6 1<%89 786 18%59 1&;6 2=%59 <=6 5=%59 1&;6 71%89 <=6 7;%89 1&;6 58%59 <=6 1:%59
TIME 2+<8 -M )S!ar! b$erva!in* 2+78 -M )En' b$erva!in*
9f the tran!it i! !et up at point 4 and a mar, i! p laced on 2% determine the follo+ing: a. b. c. d. e. f. g.
5ean horizontal angle form the mar, to the !un 5ean "ertical angle to !un 5ean time at place of ob!er"ation Green+ich ci"il time +hen ob!er"ation +a! made Sun$! apparent declination on date and time of ob!er"ation True altitude of !un corrected for refraction and paralla0 The "alue of angle ;% !un$! true bearing% and the true bearing of line 42.
SOLUTION.
a.
(mean horizontal angle) b. (mean "ertical angle)
c. (mean time at */A# longitude) d.
> 5ean Time at */A# E Time ;one orrection
(#1ui"alent Green+ich i"il Time) e. 3rom the *@ Solar #phemeri!: 3or 8 h% GT% 4pril *6 and *@% *@% the !un$! apparent declination are N *A =/.=$ and N **A 7.7$% re!pecti"el% and the difference in declination for one hour bet+een the t+o gi"en period! i! .6$. Therefore: (change in declination !ince midnight or 8h) (Declination of the !un at B.-6 h% *6 4pril *@) f.
Determining True altitude of !un: 3or a "ertical angle of =AB.$ ta,en at an ele"ation of *-6.B/m +hen the temperature i! /*.*A% the follo+ing "alue! are ta,en from table! 5e > .6= (ele"ation multiplier) 5t > .@B (temperature multiplier) P > .**$ (paralla0 correction) '" > *.*-$ (refraction "alue) (Note: When obtaining values from tables there may be a need to reform some interpolation) ' > '" (5e) (5t) > *.*-$ (.6=) (.@B) > .@7$ (refraction correction) h > h$ ? ' F P > =AB.$ ? A.@7$ F ..**$ > =A -.@$ (true altitude of !un)
g. Sol"ing for angle ; and !un$! true bearing:
$
(!un$! azimuth from north )
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Re$ul!$ an' 4i$#u$$in
Table 1:
P#$%T$%&' #% TE ')%
TELES/O-E -OSITION
HORIZONTAL ANGLE )/l#0i$e r, ,ar0 ! !3e $un*
VERTI/AL ANGLE
/=-B$
=6//$
/-/*$ /-/@$ /B==$ /B-6$ /**$ /676$
=B//$ =-//$ =-=$ =*7$ 7@-*$ 76-7$
/6-@$
7=@$
4ire#!
Rever$e'
VI%
/n#lu$in
VII%
Re#,,en'a!in)$*+ O.!inal
VIII
Reeren#e)$*+
TIME 2+<<+25 )S!ar!* /:=/:*/:==:@ /:=-:* /:-/:-7 /:-:* 7:*:<+8<+5: )En'*
Elgin, ichard !., *avid . +nowles and ose-h . 'enne, Celestial Observation Handbook and Ephemeris, !ietz o., #verland Park, +ansas. (A lot of good information in a little book."
REMAR>S? HINTS @ -RE/AUTIONS+ *.
4!tronomical ob!er"ation! a! applied to !ur"eing ba!icall in"ol"e! the determination of the po!ition of the !un or certain !tar!. 9t! purpo!e in !ur"eing i! to determine the direction of the true meridian. hen the true meridian i! determined% true bearing! or true azimuth! can ea!il be calculated. /. True direction! are needed to e!tabli!h propert line! in order that tract! of land can be correctl de!cribed. The!e direction! are al!o needed +hen retracing old propert boundarie!% in !pecifing direction! of tangent! on circular cur"e!% and for "ariou! other purpo!e!. 7. The field operation! con!i!t of mea!uring horizontal and "ertical angle! to the !un or !tar and recording the preci!e time that the hea"enl bod i! !ighted. There i! a need to ma,e !e"eral ob!er"ation! in a group. The ob!er"ed "alue! are a"eraged before being u!ed in computation!. =. To ob!er"e the !un it +ould be con"enient to ha"e four per!on!: one to hold the +hite card% one to trac, the !un +ith the upper tangent !cre+% one to tract it +ith the "ertical motion% and one to read and record the horizontal and "ertical circle! a! +ell a! the time.
-. orrection! for refraction and paralla0 ha"e to be made on all ob!er"ed "ertical angle!. The follo+ing table i! gi"en for the !tudent$! u!e.
B.
To ob!er"e the !un directl through the tele!cope eepiece ma re!ult in !eriou! inHur to the ee. 4 piece of colored or !mo,ed gla!! ma be held bet+een the ee and eepiece a! a !afet mea!ure. . The !tadia hair! !hould not be mi!ta,en for the horizontal acro!! hair. Thi! i! a"oided b rotating the tele!cope about the h orizontal a0i! until all the three hair! are !een and identified accordingl. 6. The 'oelof$! !olar pri!m i! another de"ice for ma,ing ob!er"ation! on the !un. 9t i! fitted to the obHecti"e len! of the tele!cope and allo+! the "ie+er to !ee four o"erlapping image! of the !un. The tele!cope i! !aid to be p ointed at the !un$! center +hen the cro!! hair! of the in!trument are centered on the little diamond !haped area bet+een the image! formed. @. 4 current edition of the Solar #phemeri! !hould be u!ed for obtaining po!ition! of the !un and other !elected !tar!. 9t +ill be noted that "alue! tabulated in the #phemeri! are gi"en for Green+ich ci"il time. Standard time! normall recorded for ob!er"ation! made mu!t be con"erted to Green+ich time before "alue! could be e0tracted from the #phemeri!. *. Similarl% a table +ill be needed to determine multiplier! for ob!er"ed ele"ation and temperature. The table !ho+n belo+ i! li,e+i!e pro"ided for u!e of the !tudent.
**. The mo!t !uitable time to ob!er"e the !un for azimuth! i! bet+een 6 and * 45 or / and = P5. 2et+een * 45 and / P5 the !un i! clo!e to the meridian and the !olution for angle ; of the P;S triangle become! "er +ee,. 4l!o% during the!e hour! the rate of change of altitude of the !un +ith the lap!e of time approache! zero. The effect! of refraction on ob!er"ed altitude! are !e"ere before 6 45 and after = P5. 9t i! difficult to read "ertical angle! greater than - deg !ince the ba!e of the in!trument get! in the +a of the line of !ight of the tele!cope. */. hen azimuth! are determined b ob!er"ation! on the !un% the accuracie! attained depend on man "ariable! !uch a!: +eather condition!% preci!ion of the in!trument u!ed% accurac of the time piece u!ed% abilit and e0perience of the ob!er"er!% and the cele!tial bod ob!er"ed and it! po!ition during the ob!er"ation. *7. Normall% ob!er"ation! on the !un ield a lo+ order of accurac. ith carefull e0ecuted mea!urement!% true direction! ma be determined to +ithin * to *- !econd!.
