As a rule, if the forward azimuth is greater than 180o, you should subtract 180 from the forward azimuth to get the back azimuth but if the forward azimuth is less than 180o you should add 180 to it to get the back azimuth. Is a process to get general view (picture) of the site. Local Attraction: From Point A take a compass bearing on Point B, then measure the distance between Point A and Point B. The magnetic needle of surveyor compass remains stationary at North-South direction. The local presence of magnetic rocks, iron ore deposits, steel structures, railway lines, iron electric poles etc. These reference lines are called the axes of the co-ordinates, and the point of their intersection O, called the origin.
The following are the five main methods of plotting a traverse survey: 1. But still the error may accumulate from incorrect drawing of parallel lines. A magnetic needle is provided which freely rotates over a brass circle. GIS handling | 2. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. Thanks to and with permission of Nick Hopton (UK).The product of an open compass traverse is always a polyline. The compass has to be levelled so that the measurement taken is accurate.
Databases | Annexes | Site Map, 5.4 Communication with other GIS programs, A2. If it does not, discrepancy is said to be the closing error. The sight of the line is fixed and the reading is directly taken from the top of the glass cover. By Central Meridian or Paper Protractor 4. To determine the bearing of the surveying line of sight. Measure the segment of the boundary between station 1 and station 2 and record your answer beside the azimuth reading for this segment. Join A and B2, which represents the direction of AB.
The bearings measured by prismatic compass are magnetic bearings measured with reference to magnetic north of the earth. Improper levelling and centring of the tripod.
Various mathematical tables give the lengths of chords of angles corresponding to unit radius. prismatic compass and surveyor compass are most commonly used.
3 To begin, pick the prismatic compass and locate the Starting Point (station 1). 180°. 4 To verify whether the forward azimuth reading you made is correct, exchange positions with your partner (or preferably let your partner take a back azimuth onto the sighting pole now located at station 1). By Chords. Carried out to determine and selection of suitable station points. A magnetic needle is provided which freely rotates over a brass circle. It essentially consists of a graduated horizontal circle, a pivoted magnetic needle, and a sighting device. Uploader Agreement. Walk along the boundary segment between station 1 and station 2 and make any other required readings such as resection or intersection then record such measurements on the page you have already opened. A16.2 Surveying by open-compass traverse (polyline) Prohibited Content 3. Even the chains and arrows, used in surveying, near the compass can also affect bearings.
As a rule, if the forward azimuth is greater than 180, , you should subtract 180 from the forward azimuth to get the back azimuth but. Change ), You are commenting using your Facebook account. Compass surveying is the branch of surveying in which the position of an object is located using angular measurements determined by a compass and linear measurements using a chain or tape. The method is preferred to both the above method because the direction of all the lines are plotted from a single setting of the protractor and the possible error in placing the protractor at every station is avoided. By Parallel Meridians through Each Station: Having fixed suitably, the position of the starting […] It is placed at the centre of the box to support the movement of the magnetic needle. The distance of a point from each of the axes are called its co-ordinates. To verify whether the forward azimuth reading you made is correct, exchange positions with your partner (or preferably let your partner take a back azimuth onto the sighting pole now located at station, 1). If the magnetic north is east of grid north the variation is added to the magnetic bearing). By Included Angles 3. Image Guidelines 4. The bearings shown in the table of survey data are grid bearings. By Parallel Meridians through Each Station 2. Method # 1. Stop the damp oscillations of a magnetic needle by pressing the knob containing spring brake inside to observe readings. Change ), You are commenting using your Google account. This method is the most accurate of all the methods of plotting because the use of protractor is entirely done away and each point is plotted independent of the others. A surveyor compass essentially consists of a graduated circle or disc fitted to a box. a. By Central Meridian or Paper Protractor 4. Contractor Change Order Request Excel for Project Management, Preparation of Bar Bending Schedule (BBS) and their Importance, Different Types of Estimates Calculated during the process of Construction, Indian Standard Code – IS 875 part 1, IS 875 part 2 and IS 875 part 3, Difference Between One Way Slab and Two Way Slab. The point C2 connected with B determines the direction of BC. It is basically a two-step procedure. 9 . Remember that Compass readings are made along straight segments of a boundary. Use of Surveyor Compass. You will also hand in your note book entries for grading. Make some sketches if necessary, to portray the features and positions you find in the field.