Module 3 - Phonetic Alphabet & Prowords
Numbers and Positions
What you will learn
Speak critical numbers as separate digits and give a position with the direction, reference and units needed to interpret it.
A single wrong digit can move a position, alter a channel or corrupt an identity. Standard number pronunciation and complete position structure make those errors easier to detect.
IMO SMCP says numbers are normally spoken as separate digits: 150 becomes one-five-zero. It also documents two decimal five and two point five for 2.5. A special published procedure can create an exception—for example, wheel orders use fifteen or twenty—so do not turn the separate-digit habit into an invented universal rule.
For latitude and longitude, give degrees and minutes, add decimals of a minute if needed, then state North or South and East or West. The directional letters are not optional: the same numbers with a different hemisphere describe another position.
A position relative to a mark must name a well-defined charted object. Quote the position's true bearing from that mark in 360-degree notation, then the distance and unit. Saying only 'near the lighthouse' leaves the receiver to guess both direction and scale.
Worked example
A learner must transmit 150 degrees and a distance of 2.5 nautical miles without merging the digits.
- 1Break 150 into three digits: one-five-zero degrees.
- 2Give the distance as two decimal five nautical miles, or the documented alternative two point five nautical miles.
- 3Repeat the value if it is critical or if the receiving station asks for it again.
Sense check: One-five-zero cannot be mistaken for fifteen, and the distance still includes its unit.
Build a position that another station can plot
Your plotted position is 50 degrees 42.5 minutes North, 001 degrees 18.2 minutes West.
1. Separate the digits
Say five-zero degrees four-two decimal five minutes, then North.
2. Give longitude completely
Continue zero-zero-one degrees one-eight decimal two minutes, then West.
3. Check the source
Read from the current plotted or electronic position and be ready to repeat the complete coordinate.
Sense check: The receiver needs both coordinates, both direction words and the degree/minute structure; a bare string of digits is not a usable position.
Common mistake or limitation
- Dropping North, South, East or West because the local area seems obvious.
- Giving a bearing from an unnamed or uncharted object that the receiver cannot identify.
- Inventing decimal places or precision that the position source does not support.
Recap
- Speak ordinary radio numbers as separate digits unless a specific procedure says otherwise.
- Both decimal and point appear in the IMO example for 2.5.
- Latitude and longitude need degrees, minutes and hemisphere directions.
- A relative position needs a charted mark, true bearing from the mark, distance and unit.
Optional quick check
Section 2 of 7
Which relative position gives the receiving station enough structure to interpret it?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying Phonetic Alphabet & Prowords
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