Mechanical or Tracing Paper Method

The process of mechanical method is applied using a tracing paper or cloth. The table is stationed, levelled and set at station O and is oriented as nearly as probable in its correct position either through visual judgment or by use of compass. A tracing cloth/paper is stretched and spread over the table. A position of O is guesstimated and fixed on the tracing to approximately locate the table station O on the map as o. Along with alidade centered at o and stations A, B and C are bisected and rays oa, ob and oc are drawn on the tracing. The tracing is then un-stretched and rotated until the three new drawn rays pass by plotted positions of a, b and c on the map. This will give a new position of station O on map as o?. This is transferred to map through a pin of a fine needle point.

The alidade is then placed along o?a and station A is bisected through rotating the table and then clamping it in new position. Stations B and C are after that sighted and rays drawn as check. The new rays shall pass by o′ if new table orientation is correct. Therefore, a small triangle of error might be created as table orientation was only approximate.

The above procedure is then repeated through trial and error till the triangle of error vanishes.

                                         Figure : Mechanical or Tracing Paper Method