Double rodding is a technique used in land surveying to ensure the accuracy of measurements taken with a leveling instrument, such as a level or transit. The process involves using two rods, one placed in the location where the measurement is being taken and another at a predetermined distance away.
Here is the step-by-step process for double rodding:
Set up the leveling instrument: The leveling instrument is set up at a suitable location, such as a tripod, and adjusted to be level.
Place the first rod: A surveyor places the first rod at the point where the measurement is being taken. The rod is set vertically and the surveyor reads the measurement off the rod using the leveling instrument.
Place the second rod: The surveyor places the second rod at a distance away from the first rod. The distance is typically set based on the distance that can be accurately measured with the leveling instrument.
Take the second reading: The surveyor then reads the second rod using the leveling instrument. This measurement provides a check on the accuracy of the first measurement.
Repeat the process: The surveyor may repeat this process several times to ensure the accuracy of the measurements. This is especially important when working on long distances or in challenging terrain.
Double rodding is a useful technique for ensuring the accuracy of measurements taken with a leveling instrument. It provides a way to check the measurements and ensure that they are consistent and accurate.