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LEVELING

LEVELING. (a most elevating passtime). I need to know the elevation of the ground here (so I can choose the right club). The problem:. I’m here standing on ground that’s 123.467 metres above mean sea level. The solution?. to the green. Simply extend a. from my feet. level line.

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LEVELING

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  1. LEVELING (a most elevating passtime)

  2. I need to know the elevation of the ground here (so I can choose the right club) The problem: I’m here standing on ground that’s 123.467 metres above mean sea level

  3. The solution? to the green Simply extend a from my feet level line Then measure the vertical distance down to the green.

  4. There’s only one catch… I don’t have a carpenter’s level that long!

  5. WhyBack Sight ? and this point B Any suggestions? Call this point A Sally sets up a level here Manny holds the rod on Point A Sally’s level projects a level line of sight But the reading was taken while looking Backwards The rod reading is the vertical distance between the level’s line of sight and Point A This is called a Back Sight (a rod reading taken on a point of known elevation) This is the direction of the survey, right?

  6. ? 125.448 m 1.981 m 123.467 m The Height of Instrument (HI) is The Back Sight (BS) was 1.981 m If the elevation of Point A is 123.467 m then what’s the elevation of the instrument’s line of sight? 123.467 + 1.981 = 125.448 m

  7. Only one problem… Manny’s rod, fully extended is too short to reach the line of sight TP 1 Whenever the sight is too low, too long or blocked by obstacles (trees, buildings, etc) Sally aims the scope at TP 1 and takes a rod reading of 2.216 m What now? This reading is called a Fore Sight because it was taken in the same direction as the survey (forwards) If Sally aims the level scope at Point B she could find the elevation of Point B by subtracting it from the HI then takes a rod reading In surveying we call it a Turning Point an intermediate point is required to transfer the elevation. this is a temporary point (a rock, a pipe,… a hard place)

  8. What Next? 125.448 123.590 2.216 0.358 123.232 To find the elevation of TP 1, subtract the fore sight from the HI: Sally’s got to get down! Sally takes another rod reading on TP 1 (she may as well get closer to Point B too) The BS on TP 1 is 0.358 m Elevation of TP 1 = 125.448 – 2.216 = 123.232 What type? That’s right, a back sight And the new HI is… 123.232 + 0.358 = 123.590 m

  9. Finally… 1.725 -1.602 121.865 123.590 Sally aims at Point B and takes another rod reading 123.467 The change in elevation in a leveling survey is always calculated as: DElev = Elevfinal – Elevstart Furthermore, every leveling survey starts with a back sight on a known elevation and ends with a fore sight on an unknown elevation And the elevation of Point B is… The FS on Point B is 1.725 m So what was the change in elevation from A to B? 123.590 - 1.725 = 121.865 m 121.865 – 123.467 = -1.602 m (Negative means losing elevation)

  10. Let’s look at this survey in profile view: FS BS 125.448 1.981 2.216 BS 123.590 FS 0.358 123.467 1.725 123.232 Point A First Setup TP 1 Find the elevation of Point B Given the elevation of Point A Second Setup ? HI = 123.467 + 1.981 Elev TP 1 = 125.448 – 2.216 HI = 123.232 + 0.358 Elev Pt B = 123.590 – 1.725 121.865 Point B

  11. As leveling surveys go that was pretty basic Usually several turning points are needed and the survey must end with a fore sight on a known elevation to check the accuracy Survey notes are required to document measurements and calculations Lets look at how this information is documented in field notes

  12. First of all, the field books have pages that are lined in the following format: Even numbered pages are for recording measurements and doing calculations:

  13. Odd numbered pages are for descriptive information (labels, diagrams) to explain measured data and also for project titles

  14. For the survey shown in this presentation the notes should be logged like this… Until you become experts (who don’t make mistakes) triple space! 3. Then record numbers as they’re measured or calculated There’s a way to check the math…its called the Math Check and it goes like this: 1. Identify the project and date 2. Fill out column headings as shown What club should I use? 05-09-08 FS BS HI ELEV STA Point A 125.448 1.981 123.467 1. Find the sum of the back sights (SBS) 123.232 2.216 123.590 5. Then you must confess: the notes were reduced by Sally Surveyor and the math check was performed by Manny Rodman TP 1 0.358 1.725 Point B 121.865 2. Find the sum of the fore sights (SFS) Math Check DElev = SBS = 2.339 SFS = -1.602 3.941 3. Find the change in elevation (DElev) SBS – SFS = 2.339 - 3.941 = -1.602 Since SBS – SFS = DElev 4. If SBS – SFS = DElev, then the elevations and HI’s calculated are correct \Math is Correct Reduced by: S.S. √ by: M.R.

  15. The description page should indicate who did what… Then a description of our starting point… And finally a description of our ending point… ¬ instrument rod in hand S.S.: M.R.: [123.467] Point A: 175 yd mark, centre fairway, 12th hole, South Course, Angus Glen G. & C. C., Markham, Ont. Note that description begins on same line that this point is referenced in the notes Note that there is no description for the turning point Note that the description for Point B does not include an elevation because we don’t know its TRUE elevation True elevation (known from previous surveys) Point B: 15 yd before cup, green, 12th hole, South Course, Angus Glen G. & C. C., Markham, Ont.

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