Face left observation(In theodolite survey):If the face of the vertical circle is to the left of the observer, the observation of the angle is known as Face left observationFace Right observation(In theodolite survey):If the face of the vertical circle is to te right of the observer, the observation of the angle is known as Face right observation
The 2 diagonals bi-sect each other at right angles which is 90 degrees
A face is the flat surface of an object (2 or 3 dimensional). An edge is when two sides (faces) meet on an object. A vertex is the corner of an object, where an angle exists between two or more lines.
This method is used if there are more than one angles to be measure from a certain station point. Consider the following fiqure, we will measure angles AOB and BOC using this method.ProcedureSetup the theodolite at station O, bisect the point A with a certain circle reading with face left.Rotate the instrument in clockwise direction and bisect B, note the circle reading.Then rotate and the telescope till it bisect the point C, note this circle reading also. All these reading will book into face left position.Transit the telescope and rotate the instrument through 180°, this time bisect the point C firstly and then rotate telescope in anti clockwise direction towards B and then ultimately towards A. Put these readings in face right position.You can do more than one sets of measurements for the accurate results, i have done one set and booking method is as follows,Inst. StationStn. SightedFaceCircle reading(° ′ ″)Mean of faces(′ ″)Angle value(° ′ ″)OAL10 20 5020 60AOB37 10 05 R190 20 07BL47 30 1030 11R227 30 12BOC41 10 14CL88 40 2040 25R268 40 30
In 60 minutes, the minute hand completely circumnavigates the face of the clock,and returns to where it was 60 minutes earlier. That's a travel of 360 degrees.
Face left observation(In theodolite survey):If the face of the vertical circle is to the left of the observer, the observation of the angle is known as Face left observationFace Right observation(In theodolite survey):If the face of the vertical circle is to te right of the observer, the observation of the angle is known as Face right observation
Face left observation(In theodolite survey):If the face of the vertical circle is to the left of the observer, the observation of the angle is known as Face left observationFace Right observation(In theodolite survey):If the face of the vertical circle is to te right of the observer, the observation of the angle is known as Face right observation
Face left observation(In theodolite survey):If the face of the vertical circle is to the left of the observer, the observation of the angle is known as Face left observationFace Right observation(In theodolite survey):If the face of the vertical circle is to te right of the observer, the observation of the angle is known as Face right observation
Face left and face right are taken to reset the posoition of the theodolite so additional measurements can be raken
taking readings using theodolite keeping the vertical circle of the instrument on left side of the observer is called a face left observation and to measure horizontal angle the instrument is rotated(swing) in horizontal plane with respect to the vertical axis in a clockwise direction called rigt swing.
When the vertical circle of the theodolite is to the left of observer, it is in face left position. Similarly when the vertical circle is to the right of observer it is in face right position.
measurments are a tipe of tape that measures=
Procedure:- 1) Let LOM is the horizontal angle to be measured as shown in fig. O is the station point fixed on the ground by a peg. Set up the theodolite over the peg 'o' and level it accurately. 2) Set the horizontal graduated circle vernier A to read zero or 360° by upper clamp screw and slow motion screw. Clamp the telescope to bisect the bottom shoe of the flag fixed at point 'L' and tighten the lower clamp. Exactly intersect the centre of the bottom shoe by means of lower slow motion screw. Check that the face of the theodolite should be left and the telescope in normal position. 3) Check the reading of the vernier A to see that no slip has occurred .Also see that the plate levels are in the centre of their run. Read the vernier B also. 4) Release the upper clamp screw and turn the theodolite clockwise. Biset the flag bottom shoe fixed at point M by a telescope. Tighten the upper clamp screw and bisect the shoe exactly by means of upper slow motion screw. 5) Note the reading on both the vernier to get the approximate value of the angle LOM. 6) Release the lower clamp screw and rotate the theodolite anticlockwise ai azimuth. Bisect again the bottom shoe of the flag at 'L' and tighten the lower clamp screw. By means of slow motion screw bisect exactly the centre of the shoe. 7) Release now the upper clamp screw and rotate the theodolite clockwise. Bisect the bottom shoe of the flag fixed at M and tighten the upper clamp screw. By means of slow motion screw bisect exactly the centre of the shoe. The vernier readings will bw now twice the of the angles. 8) Repeat the process until the angle is repeated the required number of times (usually 3). Add 360° for every complete revaluation to the final reading and divided the total angle by number of repetitions to get the value of angle LOM. 9) Change the face of the theodolite the telescope will now be inverted. Rrpeat the whole process exactly in the above manner and obtain value of angle LOM. 10)The average horizontal angle is then obtained by taking the average of the two angles obtained with face left and face right. 11)Usually three repetitions face left and three with face right should be taken and the mean angle should be calculated. by M.laxminarayaan
because if you change the angle, you don't see the face anymore.
*find a theodolite or total station *check for collimation *check theodolite vertical axis *set up the theodolite a distance away from the foot of the tower, or closer but using a diagonal eye piece *use left face to bisect bottom point and clamp the horizontal plate *check the tower zenith transit and use the right face to bisect the bottom point and do as explained above *dont forget to record readings of every stage.
There are two angles between 5 and 8 on a clock face. The smaller (right) angle is 90 degrees. The larger (reflex) angle is 270 degrees.
rake angle