l>6. HORIZONTAL LINES, SLOPES, contour LINES and also DIFFERENCES IN ELEVATION

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6. HORIZONTAL LINES, SLOPES, contour LINES and also DIFFERENCES IN elevation 6.1 Boning Rods 6.2 The N-Frame Level 6.3 The functional Tube Water Level 6.4 The Hand Level

Surveying or survey levelling is practised to recognize the distinctions in key (= upright distances) between various point out in the field, come measure ranges (horizontal distances), to collection out edge lines etc. Major surveying works are done by engineers or default surveyors using sophisticated equipment such as the levelling tool (see Fig. 33). This section will only address elementary equipment. Most equipment can it is in home-made and also be supplied by the farmers themselves after tiny training. Fig. 33 an example of a levelling instrumentThe various types of equipment and their use described in the sections the follow, are:- Boning rods: horizontal lines and also slopes - N-frame level: slopes and also contour lines- flexible tube water level: countour lines and differences in elevation- Hand level: edge lines and differences in elevation.6.1 Boning Rods 6.1.1 description 6.1.2 usage of boning rods

6.1.1 Description

Boning rods space T-shaped and also made that wood. Their elevation is normally 100 cm and the cross-lath is 50 centimeter x 10 cm. The bottom part is sometimes reinforced with steel (see Fig. 34).Fig. 34 A boning rod

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It is vital that all boning rods have precisely the same elevation (100 cm) and also while working through the boning rods, the sun should be maintained in the back, together it would certainly otherwise be difficult to see them. Usually a total of 3 or 4 boning rods is required.6.1.2 use of boning rods 6.1.2.1 setting out horizontal lines 6.1.2.2 setting out slopes

Boning rods are provided to set out horizontal present or lines with a constant slope. In certain they are used for setting out canal excavation works, but additionally for roads and also dyke construction. To it is in able to collection out horizontal lines or lines through a consistent slope, the elevation (or height) of 2 points ~ above the heat (preferably the beginning and end points) need to be known.6.1.2.1 setup out horizontal linesSuppose a horizontal line has to be collection out in between the Bench marks A and B. Bench point out A and B have actually the exact same elevation. The procedure is:Step 1Set out a straight line in between A and B (see thing 2) and place intermediary pegs at regular intervals (see Fig. 35a; pegs C and also D).Fig. 35a setup out a horizontal line, action 1Step 2Place boning rods on peak of the two Bench Marks and on top of peg C. The observer, looking simply over the height of boning rod A make the efforts to lug the tops of the boning rods A, B and also C in line.As can be checked out from Fig. 35b, boning pole C and also thus peg C is also high; the top of the boning rods are not in line.

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Fig. 35b setting out a horizontal line, action 2Step 3Hammer peg C more into the soil. It may be important to dig deep into some of the soil bordering peg C in stimulate to have the ability to lower peg C sufficiently.The peak of peg C is in ~ the exactly elevation when, looking end the top of boning stick A, the top of the boning rods A, C and B room in heat (see Fig. 35c).Fig. 35c setup out a horizontal line, action 3Step 4Place a boning rod on peg D. As soon as looking end the top of the boning rods A and B the is not feasible to see the optimal of the boning stick on peg D, as peg D is also low (see Fig. 35d).Fig. 35d setting out a horizontal line, action 4Step 5Replace peg D by a much longer peg or pull the end peg D and include some floor in the prompt surroundings that D and also hammer peg D again into the soil. Repeat this process until the correct elevation that peg D is discovered (see Fig. 35e).Fig. 35e setting out a horizontal line, action 5Step 6The 2 Bench point out A and also B and the pegs C and D all have the very same elevation. Line ACDB is horizontal (Fig. 35f).Fig. 35f setting out a horizontal line, step 66.1.2.2 setup out slopesThe use of boning rods when setting out a slope is the exact same as described in 6.1.2.1 only, in this case, the Bench clues A and also B perform not have actually the same elevation. Bench note A is either greater or reduced than B. As soon as the difference in elevation and also the horizontal distance in between A and B space known, the slope can be calculation (see Volume I, thing 3 and also Volume 2 thing 3 and sections 6.3 and also 6.4).6.2 The N-Frame Level 6.2.1 description 6.2.2 testing the N-frame level 6.2.3 usage of the N-frame level

6.2.1 Description

This instrument, provided to set out edge lines or slopes, consists of a wooden framework (a key lath, 2 legs and 2 overcome poles) as displayed in number 36a. ~ above the main lath, a carpenter level is firmly fixed (e.g. With metal strips).6.2.2 trial and error the N-frame levelBefore fixing the carpenter level to the frame, the instrument need to be tested to make certain that the carpenter level is in the correct position.The structure is put on two points which have actually the exact same elevation (for example on a horizontal table or top top a floor that has been checked formerly with the carpenter level). If the bubble of the level tube is not precisely in in between the marks, the carpenter level should be adjusted by placing a spacer (e.g. Thin piece of board) under one end of the level (see Fig. 36a and b).Fig. 36a The N-frame level

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Fig. 36b testing the N-frame level6.2.3 use of the N-frame level 6.2.3.1 setup out contour lines 6.2.3.2 setup out slopes

The N-frame level is used to collection out contour lines and slopes on the field.6.2.3.1 setting out edge linesStarting native peg (A), a edge line has to be set out. The procedure to follow is:Step 1One leg of the tool is put close come peg (A). By transforming the frame roughly this leg, a place of the structure is discovered such that the 2nd leg is ~ above the ground and the bubble of the carpenter level is in between the marks. This way that the clues thus uncovered by the 2nd leg that the structure is in ~ the exact same elevation as the beginning point. Both clues belong come the same contour line. A brand-new peg (peg B) is propelled in close come the 2nd leg to note the ar (see Fig. 37 a).Fig. 37a setting out a edge line, step 1Step 2The N-frame is moved to the newly-placed peg and the procedure is repeated until the end of the ar is reached. Every the pegs, for this reason driven in the ground, type a contour heat (see Fig. 37b).Fig. 37b setup out a contour line, step 2Step 3When the an initial contour line has been pegged out it can be essential to do minor adjustments by moving some of the pegs to the left or come the ideal to find a smooth line. Most of the pegs will stay in the very same place. The smooth line thus developed by the pegs represents the first contour line.Step 4The next step is to recognize the second contour line. A an option has to it is in made top top how many centimetres reduced (or higher) the next contour line must be. This selection should be based on the forced accuracy (a little difference in height method it is more accurate), the general slope the the area and also the regularity of the general slope of the area. In practice, the height distinction will vary between 10 and 50 cm.In this example, a height difference of 20 centimeter was chosen. This way that the soil level close to peg A should be 20 cm higher than the ground level near peg A (see Fig. 38). The position of peg A. Is discovered by trial and also error, utilizing e.g. The method described in ar 3.4 to measure up the vertical distance between the floor levels near A and A1. Peg (A1) to represent the beginning point that the second contour line. Now follow the procedure described over to identify the 2nd contour line (see Fig. 38).Fig. 38 setting out the second contour line6.2.3.2 setting out slopesIn addition to the determination of edge lines the N-frame level deserve to be supplied to collection out lines through a uniform slope, which is useful, e.g. For setup out furrows or ditches.ExampleSuppose the the steep of a ditch come be collection out on the ar is 1% (one percent). In bespeak to usage the N-frame level to collection out slopes, it needs a modification; one leg needs to be shortened. In this example, one leg needs to be shortened by 2 cm, together the size of the main lath is 2 m and the compelled slope is 1%. (Note 1% the 2 m = 2 cm). SeeFig. 39 modified N-frame levelA slope of 1.5% would require one foot to be 3 cm (1.5% the 2 m) shorter; a steep of 2% would need a 4 cm (2% the 2 m) shorter leg.Step 1The shortest foot of the N-frame is inserted close come the starting peg (A). By turning the N-frame about this leg, a position is uncovered such that the second leg is ~ above the ground and also the balloon of the carpenter level is in in between the marks. The clues thus uncovered is 2 cm lower than the starting point and also is significant with a new peg (peg B)(see Fig. 40a).Fig. 40a setup out a slope, step 1Step 2The N-frame is moved and also the quick leg is placed near peg (B). The procedure is recurring until the finish of the field is reached. The sequence of pegs thus placed kind a line through a steep of 1% (see Fig. 40b). This line would be, after correction, the centre heat of a ditch with a steep of 1%.Fig. 40b setup out a slope, action 26.3 The versatile Tube Water Level 6.3.1 description 6.3.2 usage of the flexible tube water level

6.3.1 Description

The flexible tube water level, used for contour lines and measuring differences in elevation, is composed of 2 staffs through a size of around 2 m and a transparent flexible tube of about 14 m long. The ends of the tube room firmly resolved to the staffs (see Fig. 41).Sometimes, a 10 m lengthy rope is resolved to the staffs to limit the distance in between the staffs. The rope hence helps to prevent damages to the tube.6.3.2 usage of the flexible tube water level 6.3.2.1 setting out edge lines 6.3.2.2 Measuring differences in elevation

The tube is filled v muddy water so that the water level is about 1 m high in each of the pipe ends. The is crucial Chat no air bubbles room trapped in the tube. Wait bubbles have the right to be removed by tapping the tube through the finger. Where the two staffs are set, the free water surface in the tube ends have actually the very same level (see Fig. 42). This is dubbed the "communicating vessel" principle.Fig. 41 functional tube water level

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Fig. 42 The "communicating vessel" principle
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6.3.2.1 setting out contour linesTo set out a edge line v a Cube water level, the complying with procedure is used:Step 1The two staffs space placed earlier to ago at the starting point significant with peg (A). After ~ the air bubbles have been removed and also the water has involved a rest, a mark is made on both staffs, denote the water level (see Fig 43a).Step 2The lead man takes one staff and also drags the tube in what appears to it is in the direction that the edge line. As soon as the tube is virtually stretched, the lead man moves gradually up and down the slope till he obtains a place where the water level synchronizes with the mark (see Fig. 43b).Fig. 43a setup out a contour line, step 1
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Fig. 43b setup out a contour line, step 2The point where the staff is climate standing is at the same level as the starting point. A second peg (peg B) is inserted at this point.Step 3The procedure is repeated, starting from peg (B), to find the 3rd point (peg C) of the edge line.Care must be take away to prevent spilling water at any time the staffs are moved. For this purpose, the ends of the tube deserve to be closed with plugs throughout transport. It is necessary to remove the plugs during the measurements, otherwise the interacting vessels rule is no applicable anymore and also measurements will be wrong.6.3.2.2 Measuring differences in elevationFor the measure up of distinctions in elevation in between two point out in the field, the tube water level is adapted. Each employee is graduated in centimetres and used as a measure staff. The zero point usually corresponds with the foot that the employee (see Fig. 44).A. Measure the difference in elevation between two near pointsSuppose the difference in elevation between two clues A and B needs to be measured; A and also B are less than 10 m apart.The very first staff is collection on allude A and the 2nd staff on suggest B (see Fig. 45). After ~ the water level in both was standing tubes pertains to a rest, a reading is do on both staffs. The distinction in elevation between points A and also B is calculation by the formula:Difference in elevation in between A and also B = reading on employee A - analysis on employee BFig 44 Graduation that a staff
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Fig. 45 decision of difference in elevation in between two near points
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In our example (see Fig. 45):Measured analysis on employee A: 0.50 mreading on employee B: 1.50 mAnswer difference in elevation in between A and also B = analysis A - analysis B = 0.50 - 1.50 = -1.00 mIn this case, the reading on staff B is higher than the analysis on employee A; the result of the subtraction is an adverse which method that allude B is below allude A.If the reading on staff B is lower than the reading on employee A, the an outcome of the subtraction is hopeful which method that point B is over point A.B. Measure up the distinction in elevation between two remote pointsSuppose the difference in elevation between two point out A and B has to be measured, and also A and also B are more than 10 metres apart.The functional tube of the tool is too quick to take just one measurement. Several procedures are needed.Step 1In in between points A and B, pegs are placed at intervals slightly much less than 10 metres (see pegs C, D and also E in Fig. 46a).Fig. 46a determination of distinction in elevation, action 1Step 2 The ago staff is collection near peg A, and also the prior staff near peg C (see Fig. 46b).Fig. 46b determination of difference in elevation, step 2A reading is make on both staffs and the outcomes written down in a book. The ago reading in one column, the front reading in another column.Between pegsBack analysis (m)Front analysis (m)A and C0.751.25Step 3Both guys move. The back staff is set near peg C and also the front staff is set near peg D. Again, readings are made and also entered in the book (see Fig. 46c).Fig. 46c decision of distinction in elevation, step 3The procedure is repetitive until the front staff is collection near peg B and also the back staff is collection near the critical intermediate peg (E in our example). The last readings room made and also written under in the book.EXAMPLE:Between pegsBack reading (m)Front reading (m)A and also C0.751.25C and also D0.521.48D and E1.230.77E and B0.411.59Total2.915.09Step 4 The distinction in elevation between point A and suggest B is provided by the formula:Difference in elevation = sum of the ago readings - amount of the front readingsIn ours example:Measured sum back readings = 2.91 m sum front readings = 5.09 mAnswer difference in elevation between A and also B = 2.91 m - 5.09 m = - 2.18 mThe an adverse result way that point B is below allude A. A positive result would suggest that point B is over point A.6.4 The Hand Level 6.4.1 description 6.4.2 usage of the hand level

6.4.1 Description

The hand level is composed of a 10-12 cm long tube through an eye piece at one end and two hair present (one horizontal and the other vertical) at the other end. Attached come the pipe is a little carpenter level (see Fig. 47).Fig. 47 A hand level

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When the operator looks with the eye-piece, the mirror inside the tube, mirrors (on the right hand side) the place of the bubble of the carpenter level. The tool is made in such a way that when the balloon is in vision on the horizontal hair line, the instrument is horizontal and the heat of vision is horizontal (see Fig. 48).Fig. 48 use of the hand level
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For higher stability the instrument deserve to be sustained by a forked bush pole, v a steel plate attached come the bottom. This assures that the tool is always at the very same height above the ground surface.6.4.2 usage of the hand level 6.4.2.1 setup out edge lines 6.4.2.2 Measuring distinctions in key

The hand level have the right to be offered to set out edge lines and also to measure the difference in elevation in between two points.6.4.2.1 setting out contour linesStep 1The forked pole is set on the starting point. The hand level is put on the crotch that the forked pole and also tilted slowly until the bubble is viewed at the horizontal hair heat (see Fig. 49a).Fig. 49a setup out a edge line, action 1

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Step 2A varying pole is carried close to the hand level, and also placed on the ground at the exact same elevation together the starting point (see Fig. 49b).Fig. 49b setting out a edge line, step 2
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Step 3Looking through the hand level, the key of the horizontal hairline is significant on the ranging pole. This have the right to be done by tying a piece of coloured cloth about the pole, or v some coloured tape. The height side of the fabric or tape must coincide through the horizontal hairline that the tool (see Fig. 49c).Fig. 49c setting out a contour line, step 3
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Step 4The ranging pole is placed around 10 to 15 metres away from the tool in the basic direction that the edge line. The assistant moves through the ranging pole slowly up and also down the slope. The observer sights the pole and follows that by rotating the instrument, hold the bubble on the horizontal hairline. Once the height of the ranging note on the pole synchronizes with the horizontal hairline, the varying pole is set on a suggest (B) which is precisely at the very same elevation as the beginning point (A) (see Fig. 49d). This allude is marked with a peg.Fig. 49d setting out a edge line, action 4Step 5The same procedure is repeated, this time beginning from peg (B), to discover the next suggest (C) the the edge line.REMARK: The hand level deserve to only be provided with accuracy approximately a distance of about 15 m. Vision will become negative beyond this distance and also accuracy cannot be maintained.6.4.2.2 Measuring differences in elevationA. Measuring the distinction in elevation in between two close pointsThe difference in elevation between two near points (A and also B) have the right to be measured with a hand level and also a i graduated staff. The procedure to monitor is:Step 1The observer takes a place about fifty percent way between the two points A and B, that are much less than 25 m apart, over this street the hand level can be supplied with reasonable accuracy (see Fig. 50a).Step 2The assistant locations the staff at suggest A. The observer sights the staff at allude A and also moves the instrument to the horizontal position. The value indicated by the horizontal hairline is read and written under by the observer (see Fig. 50b). This reading is referred to as a back reading.Fig. 50a measure the difference in elevation, action 1Fig. 50b measuring the difference in elevation, action 2Step 3The assistant to walk to suggest B and places the employee on allude B. The observer turns around, the bush pole staying in the very same spot, and also sights the staff at allude B. After moving the tool to the horizontal position, the value shown by the horizontal hairline on the employee is read and also written under (see Fig. 50c). This analysis is called a front reading. Forward analysis 1.38 mFig. 50c measuring the distinction in elevation, step 3Step 4The difference in elevation between suggest A and allude B deserve to be calculated v the formula:Difference in elevation in between A and also B = reading on A - reading on B = back reading - front readingIn our example:Measured analysis on A (back reading): 1.62 m reading on B (front reading): 1.38 mAnswer distinction in key = 1.62 - 1.38 = + 0.24 mThe result is positive, suggest B is above point A. A negative result would median that allude B is below point A.B. Measuring the distinction in elevation in between two remote points as soon as points A and also B are more apart 보다 25 m, the procedure to monitor is:Step 1Place pegs in ~ points A and B and at intervals of 25 m or much less in in between points A and also B. See instance Fig. 51.

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Fig. 51 measure the difference in elevation between two remote points A and also BStep 2The observer takes increase a position between A and also C and measures the distinction in elevation between suggest A (near peg A) and point C (near suggest C) as described in the ahead section.Step 3The observer takes up a place between allude C and suggest D. The assistant turns the staff at allude C in the direction of suggest D. The staff must stay in the very same position and also not be lifted.Step 4Measure the distinction in elevation in between points C and also D as defined in the vault section. Continue until the distinction in elevation between the last intermediate allude and B has actually been determined.Step 5The difference in key between suggest A and point B is the sum of the differences in key between suggest A, all intermediate points and suggest B.Note: The difference in elevation between suggest A and suggest B have the right to be uncovered with the formula:Difference in elevation between A and B = sum of ago readings - amount of prior readingsEXAMPLE (see Fig. 51):Between points:Back analysis (m)Front analysis (m)Difference in key (m)A and also C0.651.40- 0.75C and also D0.201.25- 1.05D and also E1.800.50+ 1.30E and also F1.750.95+ 0.80F and also B1.371.24+ 0.13Total5.775.34+ 0.43Difference in elevation between A and B = sum of back readings - sum of prior readings = 5.77 - 5.34 = + 0.43 mThe distinction in elevation is positive, which means that allude B is over point A.
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