Objective Equipment Procedure Field Notes

The main purpose of this lab is to lay out a horizontal curve using deflection angles

A horizontal curve is generally used to connect two horizontal lines of different directions to provide a smooth transition between the lines.

To specify a simple circular curve it is necessary to know the angle of intersection of the two tangent lines and the radius of the curve

Many times radius can be expressed in terms of degree of curvature

Total Station Prism Tripod Hammer Wood stakes/hubs (12+) Flagging

- Each group will stake out the center line of a horizontal curve

- The roadway width is 40 feet wide and the curve have a radius of 297.47 feet along the centerline

- The central angle for the simple circular curve is 60º57’0”

- PI station is 635+58.36- The arc definition of degree of curve should be

used

- A sketch of the horizontal curve geometry is shown in the handouts

- Calculate the stations for the point of beginning and point of ending of the circular curve (BC-EC)

- Calculate the following:- Long chord length- Degree of curvature- Length of the curve- Curve radius- Tangent length- External distance- Middle ordinate

- Each group will be assigned a PI, assume back tangent due to west. This line will be the ZERO line

- Prism person will walk out until they are on line and out the tangent length to determine BC. Stake!!!

- Turn the scope 180 degrees, turn the central angle and determine EC. Stake!!!

- Move the Total station to BC and then start to stake out the curve

- BC Sta = PI Sta – TEC Sta = BC Sta + L

- Calculate the deflection angles with the following equationDang=(C*5729.58)/(200*R)

- Every 100 feet- Stake the middle point- Calculate the chord distance from BC to every

station with the following equationChord=2*R*sin(Dang)

- The angle of deflection from BC to EC should be the half of the central angle I