In one of my previous videos we went around
Its house and took a number of readings, and we recorded them on to a rise and fall
Level book now what I wanted to do in this
video
will show you the other method which is
Referred to as Height of Collimation
So here is a height of collimation level book and the process of filling out the readings is
exactly the same as it was the rise and fall
The only thing that changes on this sheet is
instead of having a rise and a full column down here. We just have the height of collimation column, so
Process for height of collimation as far as filling it out it's exactly the same as the rise and fall
Level book, it's only when we start calculating it that it becomes different
So in order to look at our rls. We knew that our datum had an RL of 10.000m
So what we need to do is work out what the height of collimation is
for the Datum and all we do is we add our
First reading our back sight to our known RL
to give us the height of collimation for this
set of reading so hot acclamation it's just like saying what height the extra actual instrument is
so if we take 10.000m as the height of our datum
Plus our 2.395 add that together we get a height of collimation of
12.395 so for the rest of the process all we have to do is take the figure
That's in this column
Away from 12.395that will give us our RL
so 12.395 minus 2.050
It's going to give us
10.345
Now unlike the Rise and fall sheet we don't use the consecutive numbers we now go back to here
12.395 minus
1.970
Will give us 10.425
So then 12.395 minus 1.888
will give us
10.507
right 12.395 minus 1.808
will give us
T10.587
12.395 minus 1.722
will give us
10.673
Okay
12.395
minus 1.664
10.731
12.395 minus 1.609 will give us
10.786 and 12.395 minus
1.534 will give us
10.861
now
you're down to here
now we keep going, so
12.395 minus 1.493
10.980
Okay, so we're down to our first lot of readings so now the changeover. So what we do we know that
that height so
we need only to look at the height of collimation for this side, so we take our known height here and
add our backsite
So 10.902
plus 1.732
will give us a height of collimation of
12.634
we then start the process again, so 12.634 minus
1.795 will give us
10.839
12.634 - 1.859
Will give us
10.775, we keep going down
10.698
this one will be
10.622
this one will be
10.582
10.501
10.418
10.345
of course
12.634 to 2.634 minus is going to give us ten
Okay, so again we can do a couple of checks if we add up our
backsights
add up our foresites and
work out the difference
then in this case because It's a closed survey the difference should be zero
and
Same here. We can add up
will take our first RL away from our last RL and
again because this is a closed survey our answer should be zero and if
If you've done an open survey, so you haven't finished at the same point. You started then the difference between
this first check and the second check it should be the same and just
the case you don't believe me here is the rise and fall level book and
You would notice that these figures or the RLs for each point are
exactly the same so have all to the one they're right in the middle of the change point 10.902
and we go back to our height of collimation and
there at the change Point 10.902
so you go there's another method of
Calculating the RLs for the points that you've taken
Instead of using rise and fall you can always use the height of collimation method