CMCE $2322$

Lab $2$: Horizontal Curve Stakeout

Calculations

Given the following, calculate the deflection angles and chord lengths required to stake out the curve with $10\text{'}$ stations. Also solve for T $($you will need this to find the location of the PC$),$ stations of PC and PT$,$ and the long chord $($we can use this as a check for the accuracy of the stakeout$).$

$R=21ft$

$L={32}^{\text{'}}$

PI at $4+83$

Field Procedure

Pre$-$Survey Setup

The location of the PI and a direction for the back tangent $($toward the PC$)$ will be given.

Using your calculated distance for $T,$ use a tape to measure back along the back tangent and mark the location of the PC$.$

Instrument Operator:

Set up the total station and level it over the point at the PC$.$ It is important that the total station be both level and over the point.

Sight the point at the PI and set zero $($ANG button$).$ Remember to focus the crosshairs and then focus the zoom on the scope to see the mark at the PI clearly.

Turn the first deflection angle and direct the person with the rod until they are on line. When they are on line with the angle you turned you will see the center of the prism behind the crosshairs. Look over the top of the instrument to give them general directions on which way to move to get on line. An estimation of how far they need to go $($and in what direction, from their point of view$)$ is more helpful than just saying generally left or right.

Once the point for the first station has been marked, turn the next deflection angle $($keeping the same zero, set at the PI$)$ and repeat the process until you have marked out the PT$.$

Rod$/$Chain Crew:

Have one person hold the length of the first chord at the PC and hook the end of the tape over the tip of the rod. Once the instrument operator has turned the first angle, they will direct the person with the rod until they are on line. Keep the tape tight and the rod level. Once the rod is on line and the tape is tight, mark the point under the rod. Mark it carefully as you will be holding the tape at this point to measure the next chord.

After the instrument operator turns the second deflection angle, repeat the process holding the length of the second chord at the station you just marked $($not the PC$).$ Repeat the process until the rod is on line with the second deflection angle and the tape is tight. Mark the point under the rod.

Repeat step $2$ until you have marked the PT$.$

Post$-$Survey Check

Check your work using either method:

Check the distance between PC and PT using a tape. How does this compare to your calculated value for LC$?$

Set up the total station at the PI and measure the angle between PC and PT$.$ This angle should be the supplementary angle to the $$ angle. How do they compare?