30 40 50 Surveying made easy Karl Zeiske presented by: Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com Introduction This booklet will tell you • What are the main The use of levels and total instruments available today about the basic principles features of these stations is illustrated by a from Leica Geosystems; of surveying. instruments? series of practical neither does it touch on examples. In addition, their individual performance The most important • What needs to be taken applications programs are features. These aspects are instruments for surveying into account when described; these are covered by the com- are levels and total stations; measuring with a level or incorporated into the prehensive brochures, by the they are intended for with a total station? modern total stations technical consultants in the routine survey tasks. manufactured by Leica Leica Geosystems agencies, Anyone wishing to know • What are the effects of Geosystems and they solve and by the home pages in how and where they are instrument errors? survey tasks even more the Internet used will find the answers easily and elegantly. (www.leica-geosystems.com). here. • How can such errors be Equipped with the recognized, determined knowledge in this booklet, and eliminated? and with the help of the appropriate user manual, • How can simple anyone can carry out surveying jobs be simple survey tasks performed? confidently and efficiently. This booklet does not describe the range of 2 Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com Contents The level 4 Measuring distances without a reflector 19 Automatic target recognition 19 The total station 5 Setting out profile boards 20 Coordinates 6 Measuring angles 7 Instrument errors 22 Inspecting the line of sight 22 Preparing to measure 8 Inspecting the EDM of the total station 23 Setting up the instrument anywhere 8 Instrument errors in the total station 24 Levelling-up the instrument 8 Setting up the total station Simple surveying tasks 26 over a ground point 9 Aligning from the mid-point 26 Measuring slopes 27 Measuring with the level 10 Measuring right-angles 28 Height difference between two points 10 Measuring distances optically with the level 11 Applications programs 29 Line levelling 12 Calculating areas 29 Staking out point heights 13 Staking out 30 Longitudinal and transverse profiles 14 Remote heights 31 The digital level 15 Tie distances 32 The rotation laser 15 Free-station surveys 33 Measuring with the total station 16 The applications programs available 34 Extrapolating a straight line 16 Polar setting-out of a point 16 Surveying with GPS 35 Plumbing down from a height point 17 Surveys (polar method) 18 Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com 3 The level A level essentially comprises a telescope rotatable about a vertical axis; it is used to create a horizontal line of sight so that height differences can be determined and stakeouts can be performed. The Leica Geosystems levels are also equipped with a horizontal circle that is very useful for setting out right angles, e.g. during the recording of transverse profiles. In addition, these levels can be used to determine distances optically with an accuracy to 0.1 – 0.3 metres. 4 Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com The level • The total station The total station A total station consists of a Leica total stations are theodolite with a built-in supplied with a software distance meter (distancer), package that enables and so it can measure most survey tasks to be angles and distances at the carried out easily, quickly same time. Today’s and elegantly. The most electronic total stations all important of these pro- have an opto-electronic grams are presented in distance meter (EDM) and the section "Applications electronic angle scanning. programs". The coded scales of the horizontal and vertical Total stations are used circles are scanned wherever the positions electronically, and then the and heights of points, or angles and distances are merely their positions, displayed digitally. The need to be determined. horizontal distance, the height difference and the coordinates are calculated automatically and all measurements and additional information can be recorded. Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com 5 Coordinates In order to describe the Direction of reference Abscissa (x) position of a point, two P coordinates are required. y P Polar coordinates need a line and an angle. Cartesian coordinates need D two lines within an x orthogonal system. α The total station measures polar coordinates; these are recalculated as Ordinate (y) Cartesian coordinates within the given Polar coordinates Cartesian coordinates orthogonal system, either within the instrument itself X or subsequently in the office. Recalculation Y P given: D, α given: x,y required: x,y required: D, α y = D sin α D = ÷ √y2 + x2 D x = D cos α sin α = y/D or X cos α = x/D α Y 6 Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com The level • The total station Measuring angles An angle represents the The vertical angle is difference between two therefore correct only if the directions. zero reading of the vertical circle lies exactly in the Zenith The horizontal angle α zenith direction, and also between the two directions this stipulation is met only leading to the points P1 under ideal conditions. and P2 is independent of the height difference Deviations from the ideal P1 between those points, case are caused by axial provided that the telescope errors in the instrument always moves in a strictly and by inadequate vertical plane when tilted, levelling-up (refer to whatever its horizontal section: "Instrument orientation. This stipulation errors"). Z1 is met only under ideal Z2 P2 conditions. Z1 = zenith angle to P1 Z2 = zenith angle to P2 α The vertical angle (also termed the zenith angle) is α = Horizontal angle the difference between a between the two prescribed direction directions leading to (namely the direction of the points P1 and P2, the zenith) and the i.e. the angle between direction to the point under two vertical planes consideration. formed by dropping perpendiculars from P1 and P2 respectively Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com 7 Setting up Levelling-up the instrument the instrument anywhere After setting up the consists basically of a instrument, level it up thread-suspended mirror approximately with the that directs the horizontal 1.Extend the legs of the bull’s-eye bubble. light beam to the centre of tripod as far as is the crosshair even if there required and tighten the Turn two of the footscrews is residual tilt in the tele- A B screws firmly. together in opposite scope (illustration, bottom). directions. The index finger 2. Set up the tripod so that of your right hand indicates If now you lightly tap a leg C the tripod plate is as the direction in which the of the tripod, then (pro- horizontal as possible bubble should move vided the bull’s-eye bubble and the legs of the (illustration, top right). is centred) you will see how tripod are firm in the Now use the third footscrew the line of sight swings ground. to centre the bubble about the staff reading and (illustration, bottom right). always steadies at the 3. Now, and only now, same point. This is the place the instrument on To check, rotate the instru- way to test whether or not the tripod and secure it ment 180°. Afterwards, the the compensator can swing with the central fixing bubble should remain freely. A B screw. within the setting circle. If it does not, then readjustment is required (refer to the user C manual). For a level, the compen- sator automatically takes care of the final levelling- up. The compensator 8 Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com Preparing to measure Setting up the total station over a ground point 1.Place the tripod approxi- 5.Centre the bull’s-eye mately over the ground bubble by adjusting the point. lengths of the tripod legs (illustration below). 2.Inspect the tripod from various sides and correct 6.After accurately levelling its position so that the up the instrument, re- tripod plate is roughly lease the central fixing horizontal and above the screw so that you can ground point (illustration, displace it on the tripod top left). plate until the laser dot is centred precisely over 3.Push the tripod legs the ground point. firmly into the ground and use the central fixing 7.Tighten the central fixing screw to secure the screw again. instrument on the tripod. 4.Switch on the laser plummet (or, for older instruments, look through the optical plummet) and turn the footscrews so that the laser dot or the optical plummet is centred on the ground point (illustration, top right). Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com 9 Height difference between two points The basic principle of The height difference is levelling involves calculated from the determining the height difference between the two difference between two staff readings for the points points. A and B respectively. To eliminate systematic R = backsight V = foresight errors related to atmospheric conditions or B to residual line-of-sight error, the instrument should be about equidistant from the two A points. ∆H = R -V = 2.521 - 1.345 = 1.176 Reading: 2.521 Reading: 1.345 27 15 26 14 25 13 24 12 23 11 10 Virtual Archive of WILD Heerbrugg www.wild-heerbrugg.com Measuring with the level Measuring distances optically with the level The reticle carries two Example: stadia lines arranged Reading on upper symmetrically to the stadia line B = 1.829 crosshair.