|What you need to know about land preparation|
|Types of Farm Power|
All measurements should be recorded in a field book that can be easily carried in a shirt or pants pocket. There are a number of ways to record data in a field book.
The standard surveyor’s field book is set up as:
Where: B.S. = Back Sight, I.S. = Intermediate Sight, F.S.= Fore Sight, R.L. = Reduced Level
Mathematical checks must be done for each page of the survey book if using more than one page. This check will only work if each page begins with a back sight (BS) and ends with a foresight (FS). For this to occur if the page normally ends with a intermediate sight (IS) it is recorded as a foresight on that page and a BS on the first line of the next page. When many readings are taken this ensures that error location as identified by mathematical checks are restricted to searching single pages.
Sum BS -Sum FS = Sum Rises-Sum Falls = Last RL - First RL
These answers could be all positive or all negative, but they must be equal.
This is a check of the mathematics only not of the survey accuracy
To check the accuracy of the survey, the survey must be closed. A survey is closed by completing new set-ups and readings, until we return to the first point surveyed. It will be impossible for the first reading and the last reading taken during the survey to be identical. The level of variation will depend on the equipment being used and the skill of the operator. A practical limit is given for allowable error depending on the distance from the origin to the most distant point.
Allowable error over a distant measured one way:
Steep ground = (plus or minus 0.024 x square root (kilometers) meters)
Flat ground = (plus or minus 0.012 x square root (kilometers) meters)
Example of a field book and checks
The reduced level (RL) can then be plotted onto a field plan and contour lines drawn between points of the same height.