Prismatic compass — where is zero (0°) placed on the graduated circle?

Introduction / Context:Unlike surveyor’s compasses, the prismatic compass has a distinctive graduation system used to read bearings directly while sighting. Recognizing the position of zero and the clockwise graduation order helps avoid 90° misreads and ensures correct plotting.

Given Data / Assumptions:

• Standard prismatic compass graduation is clockwise.
• Cardinal points correspond to specific degree values.

Concept / Approach:In a prismatic compass, 0° is at the south end, 90° at the west, 180° at the north, and 270° at the east. Readings increase clockwise. This arrangement allows direct forward bearings when sighting through the prism while aligning the line of sight with the object.

Step-by-Step Solution:

Verification / Alternative check:Most instrument dials and textbooks illustrate the prismatic compass with this graduation; a quick look at a dial confirms the S-0° marking.

Why Other Options Are Wrong:

• North/east/west ends do not carry 0° on the prismatic compass; they are at 180°, 270°, and 90° respectively.

Common Pitfalls:Confusing prismatic with surveyor’s compass conventions; always check the instrument type before converting bearings.

Final Answer:At the south end