JE WorksRefersher 16 2 Adjustment and repairs of

Adjustments of Surveying Instruments. • Field Adjustments • The crew leader should develop a

• Major Adjustments • When an instrument has been damaged or otherwise requires

TEMPORARY ADJUSTMENTS: • SETTING UP – • FIXING OF INSTRUMENT • APPROXIMATE LEVELLING OF

PERMANENT ADJUSTMENTS OF A DUMPY LEVEL • THE VERTICAL AXIS OF THE LEVEL SHOULD

FUNDAMENTAL PLANES AND LINES OF A THEODOLITE FUNDAMENTAL LINES LINE OF COLLIMATION OR LINE

RELATION BETWEEN FUNDAMENTAL PLANES AND LINES OF A THEODOLITE THE LINE OF SIGHT IS

RELATION BETWEEN FUNDAMENTAL PLANES AND LINES OF A THEODOLITE • THE VERTICAL AXIS IS

RELATION BETWEEN FUNDAMENTAL PLANES AND LINES OF A THEODOLITE • THE AXES OF THE

ADJUSTMENT OF A THEODOLITE The adjustments of a theodolite are of two kinds :

ADJUSTMENT OF A THEODOLITE Permanent adjustments: The permanent adjustments in case of a transit

iv) Adjustment of Telescope Level or the Altitude Level Plate Levels. The axis of

Temporary Adjustment The temporary adjustments are made at each set up of the instrument

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JE Works-Refersher 16. 2 Adjustment and repairs of Surveying instrument

Adjustments of Surveying Instruments. • Field Adjustments • The crew leader should develop a set of test procedure to be used frequently for elimination of gross errors. Such tests should include a check of items such as the level, optical plummet, and tripod. In the field, adjustments should only be made when the instrument results are poor or require excessive manipulation. • Normally, each instrument should be periodically checked at a facility where the best conditions for testing are possible. Only the adjustments described in the manual for the instrument should be made in the field or shop. Do not “field strip” (dismantle) instruments.

• Major Adjustments • When an instrument has been damaged or otherwise requires major adjustments, it will need to be sent to an authorized repair shop. The instrument should be accompanied by a written statement indicating the types of repairs needed. In the case of electronic devices, the request should describe conditions under which the instrument does not function properly, i. e. coldness, dampness, etc. if a “loaner” is needed, this should also be indicated.

TEMPORARY ADJUSTMENTS: • SETTING UP – • FIXING OF INSTRUMENT • APPROXIMATE LEVELLING OF THE INSTRUMENT BY LEG ADJUSTMENT. • LEVELLING UP – • LEVELLING WITH 3 -SCREW HEAD • LEVELLING WITH 4 -SCREW HEAD • ELIMINATION OF PARALLAX – • FOCUSSING THE EYEPIECE • FOCUSSING THE OBJECTIVE

PERMANENT ADJUSTMENTS OF A DUMPY LEVEL • THE VERTICAL AXIS OF THE LEVEL SHOULD BE PERPENDICULAR TO THE AXIS OF THE PLATE BUBBLE TUBE. • THE LINE OF COLLIMATION SHOULD BE PERPENDICULAR TO THE VERTICAL AXIS. • THE AXIS OF THE TELESCOPE AND THE LINE OF COLLIMATION SHOULD COINCIDE.

FUNDAMENTAL PLANES AND LINES OF A THEODOLITE FUNDAMENTAL LINES LINE OF COLLIMATION OR LINE OF SIGHT TRANSVERSE OR HORIZONTAL AXIS OF TELESCOPE VERTICAL AXIS ALTITUDE LEVEL AXIS PLATE LEVEL AXIS

RELATION BETWEEN FUNDAMENTAL PLANES AND LINES OF A THEODOLITE THE LINE OF SIGHT IS NORMAL TO THE HORIZONTAL AXIS. THIS ENSURES THAT LINE OF SIGHT GENERATES A PLANE WHEN THE TELESCOPE IS ROTATED ABOUT THE HORIZONTAL AXIS IS NORMAL TO THE VERTICAL AXIS THIS ENSURES THAT THE LINE OF SIGHT WILL GENERATE A VERTICAL PLANE WHEN TELESCOPE IS PLUNGED.

RELATION BETWEEN FUNDAMENTAL PLANES AND LINES OF A THEODOLITE • THE VERTICAL AXIS IS NORMAL TO THE PLANE CONTAINING THE HORIZONTAL CIRCLE • THIS ENSURES THAT WHEN THE HORIZONTAL CIRCLE IS HORIZONTAL (AS INDICATED BY PLATE LEVEL) THE VERTICAL AXIS WILL BE TRULY VERTICAL. • THE LINE OF SIGHT IS PARALLEL TO THE AXIS OF THE TELESCOPE BUBBLE TUBE • THIS ENSURES THAT WHEN THE TELESCOPE BUBBLE IS AT THE CENTRE OF ITS RUN, THE LINE OF SIGHT IS HORIZONTAL.

RELATION BETWEEN FUNDAMENTAL PLANES AND LINES OF A THEODOLITE • THE AXES OF THE PLATE LEVELS LIE IN A PLANE PARALLEL TO THE HORIZONTAL CIRCLE. • THIS ENSURES THAT WHEN THE PLATE BUBBLE IS CENTRAL, THE HORIZONTAL CIRCLE IS TRULY HORIZONTAL.

Two peg test

ADJUSTMENT OF A THEODOLITE The adjustments of a theodolite are of two kinds : 1. Permanent Adjustments. 2. 2. Temporary Adjustments. Permanent adjustments: The permanent adjustments are made to establish the relationship between the fundamental lines of theodolite and , once made , they last for a long time. They are essential for the accuracy of observations.

ADJUSTMENT OF A THEODOLITE Permanent adjustments: The permanent adjustments in case of a transit theodolites are : - i) Adjustment of Horizontal Plate Levels. The axis of the plate levels must be perpendicular to the vertical axis. ii) Collimation Adjustment. The line of collimation should coincide with the axis of the telescope and the axis of the objective slide and should be at right angles to the horizontal axis. iii) Horizontal axis adjustment. The horizontal axis must be perpendicular to the vertical axis.

iv) Adjustment of Telescope Level or the Altitude Level Plate Levels. The axis of the telescope levels or the altitude level must be parallel to the line of collimation. v) Vertical Circle Index Adjustment. The vertical circle vernier must read zero when the line of collimation is horizontal.

Temporary Adjustment The temporary adjustments are made at each set up of the instrument before we start taking observations with the instrument. There are three temporary adjustments of a theodolite: i) Centering. ii) Levelling. iii) Focussing.

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