LEVELING (a most elevating passtime)

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

The solution? Then measure the vertical distance down to the green. Simply extend alevel linefrom my feet to the green

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

Any suggestions? Call this point A and this point B Sally sets up a level here Manny holds the rod on Point A Sally’s level projects a level line of sight 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) Why Back Sight ? This is the direction of the survey, right? But the reading was taken while looking Backwards

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

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

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

Finally… So what was the change in elevation from A to B? Sally aims at Point B and takes another rod reading And the elevation of Point B is… (Negative means losing elevation) The FS on Point B is m = m – = m The change in elevation in a leveling survey is always calculated as:  Elev = Elev final – Elev start Furthermore, every leveling survey starts with a back sight on a known elevation and ends with a fore sight on an unknown elevation

Let’s look at this survey in profile view: Point A Point B TP 1 Given the elevation of Point AFind the elevation of Point B ? First Setup BS HI = FS Elev TP 1 = – Second Setup BS HI = FS Elev Pt B = – 1.725

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

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:

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

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

The description page should indicate who did what… S.S.: M.R.: [ ] Point A: 175 yd mark, centre fairway, 12 th hole, South Course, Angus Glen G. & C. C., Markham, Ont. Then a description of our starting point… True elevation (known from previous surveys) Note that description begins on same line that this point is referenced in the notes Point B: 15 yd before cup, green, 12 th hole, South Course, Angus Glen G. & C. C., Markham, Ont. 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 And finally a description of our ending point…  instrument rod in hand