Hi, I'm RamI Tamimi. Today we're going to be using the surveying total station to calculate
differential level. We were able to figure out the elevations of all of our control points. So this
is technically just a different method to find the elevations of these control points. All right,
so in order to calculate the elevations, what we're going to do is set up the total station
in an arbitrary location. This is not over a point, this is just somewhere random. If you
don't know how to set up a total station, watch the video that I made describing all the details
and setting up the total station to ensure that you're getting accurate measurements. Um, after
you've watched that come back to this video. While we're set up at an arbitrary location, we're going
to be referencing a single point, this is going to be our benchmark. In today's video we're going to
be using orange as our benchmark. I like to change it up, I don't like to keep using the same things.
Orange's elevation will be given to us and based off of this elevation, the total station will
help us find the difference between the points so that we can calculate the elevations of all the
other points. Okay so with our total station all leveled, we're gonna go and sight point orange.
Now once we set up our prism it's important that we set the rod height to something that
is going to be consistent. I always like to set it to something that's going to be
over my head -- six feet looks appropriate. Okay now we will sight to this prism, okay
measure. Okay here's what we've got since we're only concerned with elevation,
the only number we're going to read is this one VD or vertical distance, that's the change
in distance in the vertical direction from this point to that back side, and it looks like it's
a -0.550. Using this number, we're going to be able to calculate the height of our instrument.
Remember location doesn't matter because all we're concerned with is the change in elevation.
All right, for the next part all we have to do is pick up this rod and set it up on all the
other points and take a foresight on every single point and record the change in vertical distance.
Okay, I'm going to go ahead and measure pink
cord cool and the vertical distance to pink is a -0.195. Next we'll head to green.
Can we shoot -- all right, here's what we got vertical distance of 0.340. Notice how this one is
positive and not negative. It'll make sense later on. Next we're going to do red, bring this into
focus and shoot. All right vertical distance 1.420. Finally, we're going to shoot blue,
okay and with blue we get a vertical distance of 1.850. That's it, that's the field procedure
of taking backsights and foresights to find the difference in vertical distance
using a total station. Let's head into the office so we can calculate our elevations.
Hello and welcome back to my office. Alright so we've completed the fuel procedure
and being able to find the vertical distances between all of these points. Let's take a look
at my computer so we can begin the calculations for elevation. So here is a sketch of where
we were at and what elevations we were taking our initial setup was right here,
we backsided orange and we had a known elevation of orange we then foresighted these four points.
And based off of our calculated instrument height, we should be able to calculate
these elevations in the first column. We have rod height, we know that when we were at orange
our rod height was at six feet, so let's go ahead and put that in.
6.00 -- now to calculate the instrument height, the formula is the elevation of the previous point
plus the rod height minus the back sight. Now don't be confused because in traditional
differential leveling. The backside is usually added to the elevation to get the instrument
height however, when you're using a total station you're actually going to do the opposite. You're
going to subtract the backsight after adding your rod height. So if we go ahead and pull out our
calculator -- so to get our hI we're going to take the elevation 602.662 plus our rod height 6 minus
our backsight which is a -0.55 ,so it'll be minus -- - 0.55 and our height of instrument is 609.212.
Now this height of instrument is going to stay the same because we didn't move the instrument
at all. If you ended up moving the instrument to cite different points that were out of your range,
you'll have to repeat this backside and elevation calculation to figure out the hI.
Okay given this new height of instrument our next column says rod height. Now it's very
possible at different shots, you had to lower the rod height you had to raise the rod height
because there was some kind of obstruction. In our case we kept the rod at six feet,
so for all of these we're going to write 6.00, 6.00, 6.00, 6.00, 6.00. Now to calculate elevation
here's the formula elevation is equal to the hI minus the rod height plus the foresight.
Again this is opposite of what we did with differential leveling. Remember that the elevation
of pink it will be hI of 609.212 minus six plus a negative 0.195. So we're going to be subtracting
0.195, and we get 603.017. Now for green 609.212 minus six plus 0.34 is 603.5. Now for red 609.212
minus 6 plus 1.420 is 604.632. And last blue 609.212 minus six plus 1. gives us 605.062
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