How Big are Your GPS's Degrees?
Published on 2008-05-10If you are close to the ecuator one degree is around 111 kilometres, one minute around 1850 metres, and one second is around 30.8 metres. So one metre is equivalent to 0.032 seconds, or 0.00054 minutes.
If your GPS gives you minutes with three decimals, as mine does, the minimum distance between two measured latitudes or longitudes is 0.001 minutes, which is around 1.85 metres. But if you move at the same time in latitude and longitude (towards the NE, for example) the minimum distance between two consecutive measurements will be 2.6 metres.
But that, again, only works if you are close to the ecuator. When you move away from it degrees of latitude remain the same but, as meridians converge towards the poles, degrees of longitude become smaller distances: when you get up to Saint Petersburg, at 60° North, a second of longitude has become only 15.4 metres, about half what it was at the equator.
In Barcelona, laying between latitudes 41.34° and 41.44°, one degree of longitude measures 83.64 kilometres, just 75% of the length of a degree of latitude. One minute is 1394 metres, and one second 23.23 metres.
If you need to know the length of a degree at a given latitude you can compute it with the calculator at the US National Geospatial-Intelligence Agency.