After reading this article you will learn about the construction and classification of scale of a map. Construction of Scales of a Map: In plotting a survey, often an object to be represented on paper is so large that it would be inconvenient to make a full sized drawing of it. The drawing or map is then made to a [...]
The three main obstacles in chaining of a line are of the following types: 1. Chaining Free, Vision Obstructed 2. Chaining Obstructed, Vision Free 3. Chaining and Vision Both Obstructed. It sometimes happens that a survey line passes through some object such as a pond, a building, a river, a hedge etc. which prevents the direct measurement of that part [...]
The setting up of the plane table includes three operations viz: 1. Levelling 2. Orientation 3. Centering. Operation # 1. Levelling: Place the table over the station-point and spread out legs to make it level and at a convenient height, preferably not above the elbow. Then oriented and centre the table approximately as explained in the following two operations and [...]
There are two main types of the field-book: 1. Single Line Field-Book 2. Double line Field-Book. The field measurements, sketches and relevant notes are recorded for future reference in a note book, known as field-book. The field-book in general use is about 20cm * 12cm and opens length wise. Type # 1. Single Line Field-Book (Fig. 3.18, b): Every page [...]
After reading this article you will learn about: 1. Meaning of Plane Table Surveying 2. Advantages of Plane Table Surveying 3. Disadvantages 4. Equipment Needed 5. General Instructions 6. Errors 7. Testing and Adjusting. Contents: Meaning of Plane Table Surveying Advantages of Plane Table Surveying Disadvantages of Plane Table Surveying Equipment Needed in Plane Table Surveying General Instructions while Plane [...]
Plotting means to represent on paper, to a suitable scale, the previously surveyed objects in accordance with their shape and size. Plotting is commenced after the field-work is over. The plotting of a chain survey is done in the following steps: (i) A suitable scale is chosen before starting the plotting work. The scale depends upon the importance of the [...]
This article throws light upon the top five instruments that are used for setting out right angles and finding the foot of perpendicular from the object on the lines. The instruments are: 1. Cross Staff 2. Optical Square 3. Prism Square 4. Offset Rod 5. Measuring Tape. Instrument # 1. Cross-Staff: It is generally found in two patterns: (i) Open [...]
The following are the points of differences between prismatic and surveyor’s types of compasses. Difference # Prismatic Compass: 1. The graduated ring being attached to the magnetic needle remains stationary when the compass-box and the sight vane is rotated. 2. The graduations are marked on the ring in a clock-wise direction with 0° or 360" at South end of the [...]
There are two forms of the compass in common use: 1. The Prismatic Compass 2. The Surveyor's Compass. A compass is a small instrument which consists essentially of a magnetic needle, a graduated circle and a line of sight. When the line of sight is directed towards a line, the magnetic needle points towards magnetic meridian and the angle which [...]
After reading this article you will learn about eight main precautions that should be taken while using a compass. Also learn about the sources of error in compass work. 1. The glass cover of the compass box gets charged with electricity when dusted off with a handkerchief or by the influence of electric charge in the atmosphere. Consequently, the needle [...]