1. Perpendicularity of an offset may be judged by eye, if length of offset is ............

2. If x is smallest division on main scale and n are number of divisions on vernier, n least count of vernier is ............

3. Reduced bearing of a line is an angle between ............

4. The best method of interpolation of contours, is by ............

5. If whole circle bearing of a line is 120°, its quadrant bearing is ............

6. A chain is made up mild steel or galvanized iron wire of diameter ............

7. If a 30 m chain diverges through a perpendicular distance from its correct alignment, error in length is ............

8. While surveying a plot of land by plane tabling, field observations ............

9. The systematic errors which persist and have regular effects in performance of a survey operations, are due to ............

10. The angle between two plane mirrors of optical square is kept ............