Types of Compasses:
- Prismatic Compass
- Surveyor’s Compass
Differences Between Prismatic and Surveyor’s Compass
|
Feature |
Prismatic Compass |
Surveyor’s Compass |
|
Magnetic Needle |
Broad Type, does not act as an index |
Edge bar type, acts as an index |
|
Needle Attachment |
Attached to the needle, does not rotate with the line of sight |
Attached to the box, rotates with the line of sight |
|
Graduated Card |
Graduations in W.C.B system with 0° at South, 90° at West, 180° at North |
Graduations in Q.B system with 0° at North and South, 90° at East and West |
|
Sighting Vanes |
Eye vane with slit, reading via prism |
Metal vane with fine slit, reading directly through the glass |
|
Reading |
Sighting and reading cannot be done simultaneously |
Sighting and reading cannot be done simultaneously |
|
Tripod |
May or may not be used |
Cannot be used without a tripod |
Calculation of Angles from Bearings:
In the Whole Circle Bearing (WCB) system, to find the angle between two lines based on their bearings, use the following example: Given the bearings of lines OA, OB, OC, and OD as 30°30’, 140°15’, 220°45’, and 310°30’, respectively, the angles <AOB, <BOC, and <COD can be calculated.