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Intro to Leveling

Leveling. Intro to Leveling. Why do we level?. To determine elevation with respect to an imaginary level surface (geoid) Leveling allows you to tie the depths acquired with the sonar to the geoid. Leveling. Equipment. Level – An instrument used for measuring vertical distances.

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Intro to Leveling

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  1. Leveling Intro to Leveling

  2. Why do we level? • To determine elevation with respect to an imaginary level surface (geoid) • Leveling allows you to tie the depths acquired with the sonar to the geoid

  3. Leveling

  4. Equipment Level – An instrument used for measuring vertical distances

  5. Compensated level

  6. Level rod A long brightly painted rod, accurately calibrated in metric units (or feet and inches), used for obtaining elevations and stadia measurements of distance in mapping with a major surveying instrument.

  7. 3 3 2 2 1 1 0 0 Leveling terminology Backsight - reading on a rod that is held on a point whose elevation has been previously determined Foresight - reading on a rod that is held at a point whose elevation is to be determined BM A BM B

  8. 3 3 3 2 2 2 1 1 1 0 0 0 Leveling terminology cont. Turning point - a temporary point whose elevation is determined by additions and subtractions of backsights and foresights respectively. BM B BM A

  9. Leveling terminology cont. Bust – Error is outside of tolerance for comparison of the forward run to the backward run Blunder – Gross error caused by human mistake Thread Interval- Difference between upper thread and middle thread, lower thread and middle thread Thread error- Inaccurate reading of rod resulting in greater than 2mm difference between thread interval

  10. TOP THREAD = MIDDLE THREAD = BOTTOM THREAD = 1048 1003 0960 0937 0892 0848 1162 1118 1072 SAMPLE ROD READING 11 10 09 Note: Tread interval from top to middle = 45 and middle to bottom = 43. Ideally, the thread intervals should be equal, however this seldom occurs in the field. Thread intervals for 3rd order levels should match within 2 therefore, this would be an acceptable reading. 08

  11. BM BM 3 3 2 2 1 1 0 0 Distance X Distance X Distance Y Importance of balancing 3 – 3 = 0

  12. Bird’s eye view of a standard level run Forward Run Backward Run -5 +5 SPUR SPUR -5 +5 +2 +2 -4 -2 -2 -3 +4 +3

  13. Bird’s eye view of a “RAINIER” level run Forward Run Backward Run -5 +5 SPUR SPUR -5 +5 +2 +2 -4 -2 -2 -3 +4 +3

  14. 3 3 3 3 2 2 2 2 1 1 1 1 0 0 0 0 Distance X2 Distance X1 Distance X1 Distance X2 Distance X3 Distance Y Distance X3 Distance X3 Sample Level Run _ 2 2 BS FS TP _ TP BS FS 3 1 The difference in elevation = 0 + (-2) + 1 = -1 m _ BS FS 1 2 What is the difference in elevation between BM A and BM B? BM B is 1 m below BM A BM A BM B Difference in Elevation = -2 m Difference in Elevation = +1 m UNBALANCED

  15. Error

  16. Parallax

  17. 3 2 1 0 Collimation Collimation – the accuracy of the alignment of the optics of the level. Poor collimation will result in gross errors and possibly a bust.

  18. 3 3 2 2 1 1 0 0 Kukkamaki setup Allow instruments to acclimate to ambient temperature for at least 10 minutes!! 10m 10m 20m 20m

  19. 3rd 1 FS1 C = ( h1 - h2 ) - 0.2 mm 20 m BS1 mm mm BS1 - FS1 = h1 BS2 - FS2 = h2 ) ) sum 3 sum 3 FS2 BS2 mm mm 2 ) ) sum 3 sum 3 KUKKAMAKI COURSE & SET UPS ROD 1 ROD 2 SET UP 1 BS 1 FS 1 10 m 10 m ROD 1 ROD 2 SET UP 2 BS 2 FS 2 20 m 20 m Paper Kukkamaki - Collimation Check Kukkamaki 1 where ) = Difference h = Height BS = Backsight FS = Foresight C = Collimation Error Instrument SN: Rod SN: Party Chief: Observer: Recorder: Rod Person:

  20. Difference < 30 Difference < 2 1653.7 70 71 72 71 1 1548.3 DE Computation 143 mm 141 mm 1) Sum all thread readings in BS column. 2) Sum all thread readings in FS column. 3) BS - FS 4) Divide by 3 5) Convert to meters 2 + 1553.7 75 73 + 1569.3 80 79 + 159 mm + 148 mm 302 mm 289 mm 3117.6 mm 3207.4 mm 3.2074 m - 3.1176 m Distance Computation 0.08980 m 1 = + 0.3 mm 2 = + 0.7 mm Top Interval > Bottom Interval, then add to Middle Hair Top Interval < Bottom Interval, then subtract from Middle Hair 1) Sum all THREAD INTERVALS. 2) Multiply by the Instruments Stadia. 3) Convert to Km. : Kahului 161 5680 1 1 No 9 196 2 1929 11/24/98 1620 1548 1477 1724 1654 1583 4645 mm 4961 mm 1628 1553 1480 1649 1569 1490 4708 mm + 4661 mm + 9353 mm FS 9622 mm BS BS - FS = 9.622 m - 9.353 m 0.289 m + 0.302 m 0.591 m x 333 196.803 m 1000 0.196 km Tip for Quick Mean 0.269 m ) 3 Stadia 0.08966 m check - (FORWARD RUN + BACKWARD RUN) 0.0897 m - 0.0907 m 0.0010 m 0.20 km Always use smallest distance

  21. 1592.7 mm 1612.0 mm 76 74 80 80 9 150 mm 160 mm + 1541.7 mm 70 71 73 72 + 1489.3 mm 10 + 141 mm + 145 mm + + + 1716.3 mm 6 5 + 1658.7 mm 5 6 11 + 11 mm 302 mm + 11 mm 316 mm + + 4850.7 mm 4760.0 mm 1668 1592 1518 4778 mm 1612 1542 1471 4625 mm 1722 1716 1711 5149 mm 1692 1612 1532 4836 mm 1562 1489 1417 4468 mm 1664 1659 1653 4976 mm 14552.0 mm 14280.0 mm 4.7600 - 4.8507 - 0.0907 m 14.280 m - 14.552 m 0.272 m 3 - 0.09067 m BS - FS = 0.316 m + 0.302 m 0.618 m x 333 205.784 m 1000 0.205 km ) Stadia ) check

  22. Newiz Paper leveling made easy!

  23. Run

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