Indiana LICA Contractor Certification Training Workshop 2008 Basic Surveying Concepts

► What you need to know to perform correct construction and checkout of NRCS practices  Ability to work with benchmarks that do not have elevations of  Ability to work with both rod readings and elevations  Ability to use the slope equation  Ability to establish your own benchmarks and turn points  Ability to perform a bench level circuit

Basic Surveying Concepts ► Benchmarks with elevations not  NRCS is using GPS survey grade equipment to survey more and more practices as we progress  Survey Grade GPS will not be using an elevation of for benchmarks most of the time  The concept is the same regardless of the elevation of the benchmark

Basic Surveying Concepts ► Waterway Scenario

Basic Surveying Concepts ► With surveys based on benchmarks with Elevation of  1. You set up your laser (on zero grade!) and take a shot (Back Sight- BS) on the benchmark  2. You add that rod reading to to get the height of the instrument (HI)  3. Then to obtain elevations you subtract your next rod readings (Fore Sights – FS) from the HI

Basic Surveying Concepts ► When you use a benchmark of a different elevation, it’s the same process

Basic Surveying Concepts ► Obtaining elevations from HI (HI – FS = Elevation) ► Ground shots and their elevations are rounded to tenths (0.X’) of a foot

Basic Surveying Concepts ► Normally when you set up you can not see the entire project from that one set-up  In these cases, you have to perform what is called a turn

Basic Surveying Concepts ► Performing a turn requires:  A solid Turn Point that will not move while surveying  A Fore Sight on the Turn Point to determine its elevation from HI  Move the instrument to a new location  Take a Back Sight on the Turning Point to determine the new HI  Continue surveying/ checkout

Taking a FS Shot on the Turn Point (TP) ► Shots on “hard” objects can be recorded as hundredths (0.XX’) of a foot ► All Benchmark shots and turn points should be this way

Basic Surveying Concepts Even hundredths are at the top of the black marks (0.02, 0.04, 0.06, 0.08) Odd hundredths are at the bottom of the black marks (0.01, 0.03, 0.05, 0.07, 0.09)

Basic Surveying Concepts -Taking a Back Sight (BS) on the Turn Point (TP) -Since we know the TP elevation from the previous Fore Sight (FS), we take a BS on the TP to obtain the new HI

Basic Surveying Concepts With a new HI established, you can continue taking checkout shots which are all Fore Sights (FS)

Basic Surveying Concepts If you can shoot the original TBM from your second set-up do so and make sure your TBM elevation checks out as the same elevation from when you started.

Basic Surveying Concepts ► If you can’t see the original benchmark or the instrument is too high for you to shoot it, you’ll have to make another turn back to complete your checkout notes. ► This has to be done to verify the math of all your shots. ► This is also how you can check to see if our TBM’s are correct… in case you are having trouble with them.

Basic Surveying Concepts ► When you begin with a benchmark and checkout your project and complete one or more turns and then turn back into the benchmark to check yourself, you have completed a bench level circuit. ► Your project checkout shots (waterway grade, bottom width, etc.) really aren’t part of the circuit as they don’t verify the shots taken on the benchmarks and turn points.

Basic Surveying Concepts ► The Slope Equation  Slope = Change in Elevation/ Change in Distance ► Example  The elevation at station is and the elevation at is ► The change in elevation is (565.5 – = 1.2’) ► The change in distance is (12+50 – = 150’) ► Slope = 1.2’/150’ = which is 0.8% ► This means that for every 100’ the constructed grade goes up or down 0.8’