Determination of Azimuth by Solar Observation

DETERMINATION OF AZIMUTH BY SOLAR OBSERVATIONS OBSERVATIONAL PROCEDURES & COMPUTATION CORRECTIONS TO OBSERVATIONS OF ALTITUDE & AZIMUTH

Department of Surveying Science and Geomatics, Faculty of Architecture, Planning and Surveying,

LESSON OUTCOMES...

At the end of the lesson, students should be able:

• To practice procedure of azimuth determination by solar (sun)

• To determine azimuth based on sun position.

LECTURE OUTLINE...

• Theory and Purposes • Equipments • Accuracy • Field Work Procedure – Sun Observation • Correction for Sun Observation • Calculation

THEORY...

• Generally made by observing either Sun or Star.

• Azimuth are same as a bearing.

• Term of Azimuth is used in Astronomy.

• Two method for determining Azimuth: i.

Altitude Method

ii.

Hour Angle Method

CONT...

ALTITUDE (Α) METHOD

• Observing using theodolite with accurate Vertical Angle and Approximate Time.

HOUR ANGLE (T) METHOD

• Longitude

of

the

place

should

known

accurately, • Hour angle require very accurate Time but not vertical angle.

PURPOSES OF SUN OBSERVATION...

• Azimuth determination is very important and common operation in cadastral work.

• It also widely used in determination of location of a points on earth surface. (x,y,z)

EQUIPMENT...

Sun Observation

• 10” and high accuracy of theodolite • Watch/time keeper Star Observation

• Geodetic theodolite • Chronometer

ACCURACY...

• First Class (1st order) = ±0.3” • Second Class (2nd order) = ±1.5” • Third Class (3rd Order) = ±5” • Lower Class (Lower Order) = ±20” – 30”

FIELD WORK PROCEDURE

• Sun Observation • 3 main elements: ‐ Altitude (α) ‐ Latitude (Ф) ‐ Declination (δ)

CONT... i.

Temporary Adjustment

ii. Get R.O - Using Compass, Assumed Bearing or Certifed Plan. iii. Insert the bearing into theodolite using face left.

R.O

CONT... iv. Booking (Face Left) �

Bearing for RO

CONT... v. Put sun flter on the telescope vi. Sight the sun using face left vii. Setting the cross tangent with vertical cross hair at left position

R.O

CONT... viii.Booking (Face Left) ‐

Record: •

Time

•

Horizonta l Angle

•

Vertical Angle

CONT...

ix. Still in face left, setting the cross tangent with vertical cross hair at right position.

R.O

CONT... x. Booking (Face Left) ‐

Record: •

Time

•

Horizonta l Angle

•

Vertical Angle

CONT...

xi. Transit the telescope to face right xii. Sight the sun using face Right, Setting the cross tangent with vertical cross hair at right position

R.O

CONT... xiii.Booking (Face Right) ‐

Record: •

Time

•

Horizonta l Angle

•

Vertical Angle

CONT...

xiv.Still in face right, setting the cross tangent with vertical cross hair at left position.

R.O

CONT... xv. Booking (Face Right) ‐

Record: •

Time

•

Horizonta l Angle

•

Vertical Angle

CONT... xvi.Turn the telescope to the R.O using face right. ‐ The horizontal angle should be difer ± 180o ‐ The limitation error = ± 10” R.O

CONT... xvii.Booking (Face Right) ‐

Record: •

Horizonta l Angle

CORRECTION IN SOLAR OBSERVATION...

Astronomical

• Celestial Refraction Correction • Parallax Correction • Semi Diameter Instrumental

• Bubble not perfectly center

CALCULATION FOR SUN OBSERVATION...

CONT...

CONT...

CONT...

CONT...

Table of Refraction & Parallax

CONT... 

Determination Latitude of Station Refer Origin Table Find Coord of Stn

NN : Coord of Origin – Coord of Stn. NS : Coord of Origin + Coord of Stn. 55763 x 0.03256/3600 = - 0º 30’ 16” Since the the stn is below from origin

Refer Origin Table

CONT... ď ˝

Table of Coordinate Origin by State:

CONT... 

Determination of Longitude: Refer Origin Table Find Coord of Stn : Stn GPS

EE : Coord of Origin – Coord of Stn. EW : Coord of Origin + Coord of Stn. Diff in Long = 15921.534 x 0.03246/3600 = + 11” 0º 0’ 1”

11” X Sine 3º 4’ 2” = 0º 0’ 0.61” Rounding 0º 0’ 0.61” = 0º 0’ 1”

CONT... 

Determination of G.T Observation: Apply to AM & PM Obsv Mean obsv 1 – 8 h = 9 03 – 8 00 = 1 h 03 m @ = 17 30 – 8 00 = 9h 30 m Mean obsv 2 – 8 h = 9 07 – 8 00 = 1 h 08 m @ = 18 00 – 8 00 = 10h 00 m

CONT...

Star Almanac

CONT... 

Determination of Polar Distance of Observation:

Refer Declination Table GT Obsv 1 X 0º 0’ 28” = 0º 0’ 29” GT Obsv 2 X 0º 0’ 28” = 0º 0’ 32” Determination of +/- = ???

Obsv 1 – Diff = 20º 49’ 42” – 29” Obsv 2 – Diff = 20º 49’ 42” – 32” Determination of N @ S refer Declination Table If Dec at time of obsv, N= Polar Dist = 90º - dec of time If Dec at time of obsv, S= Polar Dist = 90º + dec of time

CONT... 

Determination of Computation Azimuth: Refer Latitude of Station Refer Mean to Vertical Calculate using Formula PM Obsv = 360º - Result

Cos Asimuth = Cos 69º10’ 47” – (Sin 5º 21’ 50” . Sin 21º 58’ 12”) Obsv 1 (Cos 5º 21’ 50” . Cos 21º 58’ 12”) Cos Asimuth = Cos 69º10’ 50” – (Sin 5º 21’ 50” . Sin 23º 26’ 15”) Obsv 2 (Cos 5º 21’ 50” . Cos 23º 26’ 15”)

CONT... ď ˝

Determination of True RO: Calculated using Formula Refer Mean to Sun (Obsv 1 & 2) Diff = Comp Az. - Obsv. Az. Refer Mean to RO (Obsv 1 & 2) Mean Obs RO - Diff

CONT... ď ˝

Determination of Mean Grid Bearing R.O: Mean Obs RO - Diff

Refer Convergence Value

True RO obs. 1 -/+ Convergence True RO obs. 2 -/+ Convergence ((Grid Brg RO Obs 1 + Grid Brg RO Obs 2) / 2 )

THANK YOU

HAVE FUN IN DETERMINATION AZIMUTH BY SOLAR OBSERVATION