METHODS (SYSTEMS) OF PLANE TABLING :
Methods of plane tabling can be divided into four
distinct heads:

 

RADIATION
• In this method, a ray is drawn from the instrument station towards the point, the distance is measured between the instrument station and that point, and the point is located by plotting to some scale the
distance so measured.
• Evidently, the method is more suitable when the distances are small (within a tape length) and one single instrument can control the points to be
detailed.

 

INTERSECTION (GRAPHIC TRIANGULATION)
• Intersection is resorted to when the distance between the point and the instrument station is either too large or cannot be measured accurately
due to some field conditions

• The location of an object is determined by sighting at the object from two plane table stations (previously plotted) and drawing the rays.
• The intersection of these rays will give the position of the object. It is therefore very essential to have at least two instrument stations to locate any point.
• The distance between the two instrument stations is measured and plotted on the sheet to some scale.

 

TRAVERSING
• Plane table traverse involves the same principles as a transit traverse.
• At each successive station the table is set, a foresight is taken to the following station and its location is plotted by measuring the distance
between the two stations.
• The method is widely used to lay down survey lines between the instrument stations of a closed or unclosed traverse.

 

RESECTION
• Resection is the process of determining the plotted position of the station occupied by the plane table, by means of sights taken towards known points,
locations of which have been plotted.
• The method consists in drawing two rays to the two points of known location on the plan after the table has been oriented. The rays drawn from the unplotted location of the station to the points of known location are called resectors .