Friday, January 6, 2017

Curves - Degree (Chord and Arc Definition) - L,T,E,M,Lc,PT,, PC

If you are given with the degree, angle of intersection and Station of PI, how to find the L(length of curve), T(Tangent length), E(External ordinate), M, Lc(Length of chord), PT(Point of tangency) station, PC(Point of Curvature) station. The formulae and example is given in the following images.

Example has three parts, each part is a different question in itself.


Thursday, December 22, 2016

How to Draw Contours using Judgement and Free Hand Method


There are other method of contouring like the arithmetic estimation, but for less accurate but quick draw, one can use their fine judgement and free hand technique to draw the contours for the given elevation points. 
In the following example, the control points are already drawn. The square patterned control points' elevations are shown, one has to use the fine judgement to draw the contour lines. See how it is done, all you have to do is to judge the contour line's placement from the given elevations. 

Look at the nearest control point elevations. If the nearby elevation is higher, then the terrain is rising towards it, if it is lower, terrain must have a downward gradient. 
Definitely the higher contour must lie towards the rising terrain and a contour with the lower elevation must lie towards the downward gradient. 

Drawing Contour Lines free hand with fine judgement
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Elevation of Intermediate Stations in Leveling - Height of Instrument Method


In a profile leveling process, in between two turning points(TPs), there are many intermediate stations that we take readings to find out the elevations of the those stations. These readings can be taken using a level, a theodolite or a total stations. Problem is that how to find out the elevation of those stations. Using a bench mark and its given elevation it can be learned from the following example. The method used is generally known as the Height of the Instrument method. If you have any doubt please let me know in the comment box.

Height of the Instrument Method - Profile leveling - Elevation of intermediate stations.

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Closed Traverse - How to find out the Bearings of Traverse Lines

Let us learn to find out the bearings of the lines of a closed traverse with the help of the following example.  such problems occur in the Compass traverse or Theodolite Traversing.

you are given a closed traverse with four sides, three of its interior angles A, B and D are given. Find out the bearings of the four lines if the bearing of the line AB is given.

closed traverse- Compass survey - finding out Bearings of lines.
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Friday, October 7, 2016

Error and Correction in a Closed Traverse by Compass Surveying.


A closed traverse constructed after doing a compass survey can be checked for error by a simple formula.
As per the geometry, in a closed traverse with 'n' number of sides the total sum of the interior angles = (2n-4) * 90 degrees.

Example: Consider a pentagon with five sides and five number of interior angles A, B, C, D and E.

Sum of the interior angles = (2*n - 4) *90
= (2*5 - 4) *90
= 540 degrees.

If it was a hexagon, then n= 6
and sum of interior angles would be
= (2*6 - 4)* 90 =720 degrees

Apply this check to the closed traverse at hand and see the error.

Error =
Sum of the given interior angles - (2n- 4)*90

Correction = - Error.

Generally the error is equally divided among the interior angles of the traverse. So correction for each angle  = - (Error) / n

If the exterior angles are given, then the total sum of the exterior angles = (2n+4)*90
remember an exterior angle = 360- interior angle.
For example exterior angle at A = 360- Int. angle A.

Calculate the Error, E = Total Sum of exterior angle - (2n+4)*90
Correction = -E
Divide the correction equally for each angle = -E/n.

Thank You!

Saturday, January 2, 2016

Happy New Year to Surveyors- Why no new posts?

Its been a long time since I came here to write a blog post. I feel that if I stay away a little longer I will get kind of disconnected. Its a new year, and like everyone else, I have new hopes and aspirations. 

To keep the connection with my lovely readers is one of my resolution, and it feels really awesome while I write this post. This blog has reached more than 1,50,000 views and is among the top viewed blogs that I write here. As you can see in the side links, there are around fifteen other blogs that I write, and only few of them are competitors of this blog.

One reason that I am not able to write here new posts, is that I am no more a Surveying teacher, and I am out of ideas and topics to write anything about. However I want to write here new posts, and as soon as I get the new ideas I will post here. If you can suggest me anything, please leave a comment, and I will see what I can do. 

Thanks! and once again a very happy new year to you.

Thursday, July 9, 2015

Survey camp is not just a technical training.


This was long time ago when I posted here my last post, and if you have subscribed to my blog then you might be angry with me. Well, I am sorry, and hey! this is a technical blog, so better I come to the business at hand. I have nothing much technical to write here today, I want to ask a simple question from my readers, do you think that survey camp is more than just a technical training?

If yes, then please do comment about the experiences that you had in your weeks of togetherness with you batch-mates. Generally the camps are held at some wild terrain, having numbers of small or big hills and valleys. This is necessary because one has to learn to find out the contours and thereby draw them on the sheets.

Various streams or roads are to be accurately located and thereby drawn on the sheet. Theodolite and plane tables are the two most necessary instruments that are to be employed, right? But, there is something more important than all these things.

What is that? Its the team work and mutual understanding. The co-operation is highly required, and if its not there, it has to be built here. You might love or hate someone in your team, but at the best you have to do your work, and make up to each other for any differences. This is the reason that Survey camp is not merely a technical training but a personality building training as well.

If you are to take a reading with Theodolite, there has to be someone standing with the graduation staff at the target. Similarly, if you have to draw a line on your sheet in the plane table, one of your team member has to be there at the target. Same goes with the chaining or even in compass survey,

What do you say?

Please share your views!

Thank you!