Hi, I'm Rami Tamimi. In the last few videos,
we've talked a lot about differential leveling and how it could be used to find elevations of various
points. Today we're gonna be demonstrating profile leveling and how we can use the differential level
sidewalk by taking different elevation shots
at different distances of the sidewalk. These various distances are called stations,
and at every station, we're gonna have a different elevation that we're working with.
The different elevations will determine the slope of our sidewalk.
Now to do this we have three steps that we need to follow. First we need to mark out where all
of these stations are on the sidewalk. Second, we're then going to be foresighting our level
at all of these stations to find the elevations of these points. And third, we're going to bring
in all the data to the office and physically plot all of these points so that we can see the slope
change on a graph. All right, let's get started. [♫Music♫]
[Objects clank as he picks them up rooting through the trunk]
All right so what we're gonna need to do is measure out the length of the sidewalk. We're
gonna use this 200 foot tape to pole 150 feet. That's the length of the sidewalk. You could also
pace out the distances which I have explained in a previous video of mine, so you should go check
that out if you haven't already. But because we're looking for a little bit more accuracy,
a surveyor's tape should be just fine. We're gonna pole out 150 feet to measure the sidewalk and then
we're gonna subdivide the sidewalk into chunks of 25 feet. For every 25 feet, we're going to be
placing a wooden stake. All right. Let's do this. So what we're gonna start by doing is driving the
tape in with this chaining pin. [♫Music♫]
And now we're gonna pole 200 feet. [♫Music♫]
All right and now we're at 150 feet. I'm gonna set this, all right,
right on the ground like that. All right, we have measured out 150
feet. I'm gonna go ahead and place a wooden stake at every 25 feet to indicate our 25-foot stations.
[Wind blows] [Pounding noises]
All right. We're good. So as you can see now,
we have points at every 25 feet along this 150 foot long sidewalk. The next step is going to be
to pole out our level so that we can begin our profile leveling. To learn more about
leveling and how a level is used, check out my last video about field procedure in leveling.
[♫Music♫] [Wind blows]
Okay. Remember to step on the legs before you do any kind of
leveling. [♫Music♫]
Okay that looks good. All right, to begin the process,
we're gonna need to take a benchmark just like we did last time. For this example,
I'm gonna use this manhole right here as we have a known elevation on this manhole. Once we have
taken the backsight of this manhole we can then begin to take the readings on all of the stations.
And for the benchmark we are reading
4.95 -- 4.95 -- all right. Now we can begin to profile level our sidewalk.
And we are reading 4.55 -- 4.55 -- okay. He's gonna walk over to the next one,
so I'm gonna go ahead and position myself. 4.63 -- 4.63 -- and we're getting a 4.77.
All right let me go around here. I'll change our position.
4.89 -- 4.89.
This one is 5.01.
This one looks like it's gonna be 5.10.
And the last one looks like 4.98. Interesting. It went down.
Now, just like last time, we need to take a turn point to close out our level loop. I'm gonna be
using this manhole right here and that'll be our turn point. We'll then reset our level
and shoot back to our benchmark. Let's go. [♫Music♫]
Okay, that's -- all right. Good. Now we're gonna reset, backsight that last manhole
we shot and then foresight our benchmark [♫Music♫]
All right, now we're gonna take a backsight on the manhole.
All right, good. And now foresight on the benchmark.
Good. All right,
that's it. You now have all the data you need to calculate your profile. Let's head into the office
and plot out the profile of our sidewalk. [♫Music♫]
Hello, and welcome to my office. I am still in this space. Eventually I will get a real office.
Okay, we're gonna go ahead and take a look at the data that we collected in the field
for our profile leveling. Here you see all the data that we captured. Just like before,
we have our elevation on our benchmark. The backsight of our benchmark. And these are all
the rod shots that we took along the profile of the sidewalk. This is the foresight on the
turn point. The backsight on the turn point and the final foresight on the benchmark. If
you missed the last video I made talking about how to calculate HI elevation and adjusted elevation,
go ahead and click on the link below or on the "I" in the right hand corner and watch
that video first. I feel like it will give you more clarity about what you're looking to do
before you do the calculations here. All right, let's get started. So the first thing we want
to do is calculate our height of instrument and our elevations on all of these shots.
So we're gonna start with the elevation of 766.50 and we're going to add the foresight,
4.95 from our benchmark -- 766.5 plus 4.95 gives us an HI of 771.45. Now the rod shots are treated
exactly the same as foresights. These are going to be subtracted from the height of the instrument
and they're going to give us elevations on all of the stations. So for station zero plus zero-zero,
we're going to take 771.45 and we're going to subtract 4.55 and the elevation at station zero
plus zero-zero is 766.90. Now this HI remains the same all the way down until you get to here. So
we don't have to recalculate this HI over and over again. So using the same HI, 771.45 we're
going to then add 4.63 and we get 766.82, 771.45 minus 4.77 equals 766.68 minus 4.89 -- 766.56
minus 5.01 -- 766.44 minus 5.10 -- is 766.35 and lastly, 771.45 minus 4.98 --- 766.47. And
now this last foresight continues to have the same HI because again, we didn't lift the instrument.
It was at the same setup. So we can continue to assume that the HI is 771.45 and the only thing
we need to do is now subtract the foresight from it, 771.45 minus 4.76 gives us an elevation of
766.69. Okay, now we need to calculate the new HI. Since we picked up the instrument.
And we backsighted the turn point so 766.69 -- we're going to add 5.03 gives us a new HI of
771.72 and now the foresight to the benchmark, so now we're going to subtract
5.22 from this new HI -- minus 5.22 -- gives us 766.50. And as you can see here, the elevation
here and here are the same, which means we have no error. If you have error, refer back to my last
video to learn how to adjust your elevations. All right, now we have our elevations figured
out. We know exactly where every station lies on this profile. So now we're going to graph
out what our sidewalk looks like in terms of a profile elevation. You can do this on Excel. You
can do this by hand. It's really easy to do on Excel. All you have to do is select the columns.
One side for the stations, another side for the elevations. You go into the insert tab and select
a scatter plot with smooth lines and points. And it'll generate a graph for you. You can then edit
the axis and the title and make it look nice and presentable. I actually did this and here is the
result that I got. At the first station, we were at this elevation. We slowly started to go down an
elevation as we moved further in our stationing. Once we got to a certain point, though,
I noticed that the elevations started to go up. If you notice in my video in the background,
you can see where the elevation actually starts to go up on the grass. My only assumption is that
there must be some kind of ditch in that area. And whoever designed that sidewalk mimicked the
ground as much as they could while trying to keep it flat as possible. And you can see here with our
calculations from our level. So those are the calculations for profile leveling. Very simple,