Wednesday, November 22, 2017

Solved Example-Distance of a Point from a Line, whose end Co-ordinates are given.


The X and Y co-ordinates(in meters) of station Shore are 246.87 and 659.46 respectively, and those for station Rock are 437.85 and 973.48, respectively. The azimuth, bearing, and length of the line connecting station Shore to station Rock are 31d,18 m, 24 s,  N31 d18 m 24s E, and 367.540 m, respectively.
What is the perpendicular distance of a point from the line if the X and Y coordinates of the point are 414.278 and 959.083, respectively?


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Let me know, if you have any doubt.

Tuesday, November 7, 2017

solved Example - Find the elevations at full and half stations along sag curve

A -2.8% grade line meets a +3.6% grade line at station 125+00.  Elevation=1631.04 ft. Determine the elevation of all full and half stations if a 650-ft curve is to be used.


Solution of vertical curve length, that passes through a fixed point elevation - solved example.

A -4% downgrade intersects a +3% upgrade at elevation 120.00 ft at station 95 + 00. it is desired to pass a vertical curve through a point of elevation 128.00 ft at station 96 + 00. determine the curve length required.


Tuesday, April 18, 2017

Solved - Vertical parabolic curve - PVI, PVC and PVT and Elevations at different stations along Curve

Here is the example which shows you how to solve for the vertical transition curve elevation.

Problem: A 3% grade intersects a -2% grade at station 4+350m with an elevation of 190.5m. Given that a 250m symmetrical parabolic curve highway is utilized, determine:
elevation in meters at station 4+240
elevation in meters at station 4+260
elevation in meters at station 4+280
elevation in meters at station 4+300
Vertical Parabolic curve - PVI, PVC and PVT

Solution: Please refer the images below.
Parabolic vertical curve - elevation at stations along curve


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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Solved Example-Distance of a Point from a Line, whose end Co-ordinates are given.

Hi, Problem: The X and Y co-ordinates(in meters) of station Shore are 246.87 and 659.46 respectively, and those for station Rock are 437...

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