Gridsquares
Related wiki pages: Propagation, Calculators
What is it?
Gridsquares - otherwise known as "Maidenhead QTH Locator System" is the system recognised by the International Amateur Radio Union (IARU) for QTH location.
How accurate is it?
Compared to the conventional degrees/minutes/seconds system, most gridsquare calculations are relatively inaccurate. each gridsquare is usually 5 minutes of longitude deep and 2.5 minutes of latitude wide. In terms of distance, one minute is equivalent to one Nautical Mile on the surface of the earth (approximately 1.6km). Hence each gridsquare had an area of approximately 12.5square nautical miles (32 square kilometres).
How are gridsquares calculated?
Gridsquares are usually expressed as a six character reference, eg QG62ll. This is sometimes extended to 8 characters giving increased accuracy of location.
Using the example of QG62ll:
- The first two characters QG represent an area <math>20^0</math> wide and <math>10^0</math> high (about 720 000 square mi or 1 843 000 square km)
- The second pair of characters 62represents a rectangle <math>2^0</math> wide and <math>1^0,</math> deep (approximately 120 square mi or18400 square km)
- The final pair (often written in lower case) ll represents a square approximately <math> 3.5^0 </math> by <math>3.2^0 </math> (approximately 10.8 square mi or 27.5 square km)
How do I convert from qridsquares to degrees/minutes/seconds?
A number of very good online conversion programs ara available including: