PLANE TABLE SURVEYING AND ITS ADVANTAGES AND DISADVANTAGES
Plane Tabling
Plane Table is called the father of “Mapping”. It is used to prepare various maps in the field. It is a graphical method, where observations, mapping and contouring, proceed simultaneously. It is a time-consuming and laborious process to create a map, but is a more accurate approach. The plane table consists of a wooden drawing board with arrangement of fixing it on a tripod. With the availability of Total Station, GPS, satellite images and LiDAR data, Plane tabling methods of surveying are almost obsolete now-a-days.
Plane table Surveying also called plane tabling, is a method of surveying in which field-work and office work are done simultaneously on a plane table. The field observations are taken and recorded side by side on the sheet fixed upon the plane table and a map of the area is obtained. The use of field-book is altogether eliminated.It is most suitable for the survey of details between stations which have already been fixed by theodolite or any other accurate method of surveying. It is commonly employed for small and medium scale mapping of comparatively large areas where great accuracy is not the main consideration such as for topographical surveys.
The equipment essentially needed for plane tabling is a plane table or drawing board which carries a drawing sheet and is mounted on a tripod stand and an alidade which provides line of sight and a straight graduated edge.
Advantages and disadvantages of plane table surveying
Advantages
(a) The map is prepared in the field; therefore, the office work is minimal.
(b) The observations and plotting are done simultaneously, and the surveyor can see the terrain before him/her, so chances of losing the details are rare.
(c) Errors in plotting the details on plane table can be checked by drawing the check lines using several methods.
(d) The angles and distance measurements can be obtained graphically, and hence there is no need to carry out measurements in the field.
(e) Many far-off objects/details can be plotted accurately using intersection method to prepare the map in shortest time.
(f) It is advantageous in magnetic areas where compass survey is not reliable.
(g) Plane Table Survey is a very swift method of surveying.
Disadvantages
(a) Plane tabling work is dependent on weather conditions (e.g., rains, high winds).
(b) The plane table is not very much suitable in a dense forest area or urban area.
(c) If survey map is to be replotted at some different scale, entire work has to be redone.
(d) Its accessories are heavy to carry in the field from one location to another.
(e) The paper maps are subject to shrinkage or expansion while working in the field for long time.
(f) It is laborious and time-consuming to prepare map of a large area
(g) It requires large manpower for doing various activities from observations to plotting.
(h) If the survey is to be re‐plotted to a different scale or quantities are to be computed, it is a great inconvenience in absence of the field notes
