I have a $\text{i2c}$ GPS module I got working yesterday, and here are my co-ordinates.

  • Latitude: 44.901354999999995
  • Longitude: -68.97112333333333

What I am having trouble figuring out is that position: what size is it, with 14 significant figures? Is it 1 square foot, or the head of a pin?

Granted, the polling program I wrote could be more efficient, and poll more frequently, but it seems like the co-ordinates are little blocks or areas. Perhaps if I had greater accuracy, it would seem like a point.

So my question is:

With 14 significant figures in a GPS co-ordinate, am I right on top of that point, or in proximity to that point, where greater accuracy would put me in closer proximity?

  • $\begingroup$ Question requires drastic editing. Please correct the grammar and format your question. $\endgroup$ – SchrodingersCat Oct 10 '15 at 15:20
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    $\begingroup$ GPS does not give you 14 significant figures, even if you averaged billions of points. But, given some numbers of real significant figures it is fairly straightforward to figure out the area it could represent on the surface of the Earth. Fairly, depending on just how precisely you need it... $\endgroup$ – Jon Custer Oct 10 '15 at 15:29
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    $\begingroup$ @j0h: "Also, capitalizing i seems like an ego maniac thing". It's how English is written. In German the subject of a sentence is capitalised. An 'ego maniac' thing? Dear G-d... $\endgroup$ – Gert Oct 10 '15 at 16:12
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    $\begingroup$ Would GIS be better for this? $\endgroup$ – user10851 Oct 10 '15 at 17:02
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    $\begingroup$ It's more like 5-15 m (worse in z, and in various bad conditions). Excepted with the help of DGPS or even smarter tricks. $\endgroup$ – Fabrice NEYRET Oct 10 '15 at 17:33

Latitude: 44.901354999999995

The first thing you should notice are the repeating digits at the end of the number. This makes me suspect that the last 9 digits are spurious. In which case the Latitude indicated is 44.901355

Due to the non-spherical shape of the planet, one degree of latitude varies in length from 110.567 km at the equator to 111.699 km at the poles.

what size is it

So the difference between latitude 44.901354 and latitude 44.901355 is around 0.111 meters.

The length of one degree of longitude varies from 0 at the poles to 111.321 at the equator. At a latitude of 45, one degree of longitude is about 78.8 km.

Most low-cost GPS systems are only accurate to a few tens of meters, or to no better than a meter or so when using WAAS/EGNOS etc.

With 14 significant figures in a GPS co-ordinate, am I right on top of that point

There's a good chance you are within 30 meters of that point. The precision displayed greatly exceeds the accuracy of the system. The last ten digits are spurious.

Note that much more expensive augmented / differential GPS systems used by, for example, surveyors can produce higher accuracies.

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