Correct Answer - Option 4 : When the traverse is so short that accumulated errors in carrying the azimuth forward might be greater than orientation by compass.
Concept:
Orientation of plane table by trough compass:
The compass, though less accurate, often proves a valuable adjunct in enabling the rapid approximate orientation to be made prior to the final adjustment. The plane table can be oriented by compass under the following conditions final adjustment.
- When speed is more important than accuracy
- When there is no second point available for orientation
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When the traverse is so long that accumulated errors in carrying the azimuth forward might be greater than the orientation of the compass
- For approximate orientation prior to final adjustment.