difference between prismatic compass and surveyor compass
Prismatic compass and surveyor’s compass are both instruments used in surveying and navigation, but they have some key differences in their design, features, and applications. Here are the main differences between them:
Design and Construction:
Prismatic Compass: A prismatic compass consists of a magnetic needle mounted on a pivot, which aligns itself with the Earth’s magnetic field. It has a prism attached to the sighting system, which allows the user to simultaneously see both the magnetic needle and the target through the prism.
Surveyor’s Compass: The surveyor’s compass has a magnetic needle mounted on a pivot like the prismatic compass. However, it does not have a prism or a sighting system. Instead, it has a sighting vanes and a compass box to indicate the magnetic direction.
Sighting and Accuracy:
Prismatic Compass: The prismatic compass offers more precise sighting because of its sighting system with a prism. The user can align the target and the magnetic needle accurately, resulting in better readings.
Surveyor’s Compass: The surveyor’s compass relies on sighting vanes, and the user’s eye estimation for aligning the compass with the target. This method might be less accurate compared to the prismatic compass.
Use in Surveying:
Prismatic Compass: Prismatic compasses are commonly used in preliminary surveying work, reconnaissance, and rough surveying tasks. They provide quick and straightforward measurements of angles and bearings.
Surveyor’s Compass: The surveyor’s compass is more commonly used for basic surveying tasks, traverse surveys, and compass surveys, where moderate accuracy is required. It is often used in geodetic surveys and engineering projects.
Graduations and Readings:
Prismatic Compass: Prismatic compasses often have graduations in degrees and sometimes in mils. Readings can be taken directly from the compass dial through the prism sighting system.
Surveyor’s Compass: The compass box of the surveyor’s compass has a graduated circle, and the user reads the magnetic bearing directly from the compass box without the need for a prism.
Prismatic Compass: Prismatic compasses are relatively more compact and lightweight due to their design with a prism and sighting system, making them more portable and suitable for fieldwork.
urveyor’s Compass: Surveyor’s compasses are generally bulkier and heavier compared to prismatic compasses, which may make them less suitable for extended fieldwork.
In summary, the prismatic compass offers more precise sighting and is suitable for rough surveying tasks, while the surveyor’s compass is commonly used in basic surveying work where moderate accuracy is sufficient. The choice between these instruments depends on the specific requirements and the level of accuracy needed for the surveying project.