FIELD WORK PROCEDURE
Field work procedure in chain surveying shall be carried out as per the following steps.
1.first Reconnaissance:
Earlier to the starting of survey work, the surveyor should walk around the whole area to be surveyed, and check the possibility of arrangement of frame work. During his investigation, he should also fixes the best positions, of survey stations and survey lines. He should ensure that the whole area is enclosed by main survey lines and satisfied the principle of working from whole to part, while conducting reconnaissance.
2.second Index Sketch:
While reconnaissance of the area, the surveyor should prepare a neat hand sketch showing the arrangement of the frame work and approximate positions of the objects . In the Index sketch, the base line, names of the stations should be marked. Names of the stations should be carefully given, as the entire field works is carried out according to the sequence given in the Index sketch.
3. Third Marking the Stations on The Ground:
After reconnaissance the survey stations are marked on the ground by wooden peg They are driven into the ground firmly, projecting 25 mm above the ground. The station point is marked with a cross so that, the location can be traced, even the peg is removed by somebody
4. Fourth Reference Sketches for Stations:
To take precautions against station pegs being removed or missed, a reference sketch should be made for all main stations. For this, measurements are taken from at least two objects to the station and a sketch is prepared showing the location of station with reference to the objects.
5.final Taking measurements of survey lines and offsets and entering them in the field book:
They are following steps
(1) Ranging and changing is started from the base line, and should be measured carefully.
(ii) The magnetic bearings of the base line are measured with prismatic compass and noted in the field book.
(iii) The offsets are measured with a tape and they are noted in the field book according to their position i.e., left or right of base line.
(iv) Then the other survey lines are ranged and chained, according to the sequence of the traverse, and the offsets are taken simultaneously.
EQUIPMENT REQUIRED FOR PLOTTING
There are following types
1. Drawing board
2 Mini drafter
3. Set squares (45°, 30° and 60°)
4. Protractor
5. Scale set
6. Instrument box.
7. French curves.
8. Drawing paper
9. Pencils of good quality HB, H, 2H,
10. Eraser of good quality.
11. Drawing board clips
12. Ink and inking pen (Hi-tech pen)
13. Colours and brushes
14. Handkerchief, knife etc.
PLOTTING A CHAIN SURVEY FIELD WORK
Drawing details to scale on a drawing paper from field measurements is known as plotting. The following procedure can be adopted for plotting a chain survey field work.
1. A suitable scale is selected so that the entire area can be plotted with in the space available on the map.
2. A 15 mm margin is provided on all sides, but on left hand side a 30 mm margin may be provided for filing purpose.
3. A title block is prepared on the right-hand bottom corner and convensional symbols used in the map should be shown on the right hand side over title block
4. The north line is marked on the right hand top corner, as per the bearings observed in the field and preferably it may be vertical
5. First of all the base line is drawn on the sheet, so that the whole area along with all the objects can be drawn within the space available in the map.
6. Now, the entire frame work is completed with all survey lines, check lines and tie lines. If the error is not much, it can be suitably adjusted, but when it is large, a resurvey has to be done in respect of those lines.
7. After the network of chain triangles are plotted and checked as above, the other details are plotted by means of the offsets.
8. The main stations, subsidiary stations, chain lines, objects etc. should be shown as per the standard symbols.
9. The heading may be written on top or bottom of the map and the scale of the map is drawn below the heading
10. Unnecessary lines, objects etc. should be erased.
11. The inking of the map should be started only after completion of the pencil work in all respects.
12. Proper color conventions may be used while plotting. The inking should be begun from the left-hand-side towards the right hand side, and from the top towards the bottom.