Swift: Coordinates not accurate when using latitude/longitude

Question

I'm using the CLLocationManager in Swift. When I display location.coordinate, it provides me with the result:

37.787358900000001, longitude: -122.408227

However, if I display. location.coordinate.latitude, the result is

37.7873589

Do you know how I can get all the decimals?

Thanks, Thomas

Actually, if I've understood correctly, this is only a matter of millimeters? — ThomasTe, Jun 21 '18 at 10:00
The extra decimals are a result of [this](https://stackoverflow.com/questions/588004/is-floating-point-math-broken). — vacawama, Jun 21 '18 at 10:06
do you use "Float" type variable for lat long, or "CLLocationDegrees"? — Muhammad Ahmed Baig, Jun 21 '18 at 10:20
Changing the last `9` to an `8` would result in a change of about 1 centimeter. The GPS system is not accurate to even that level, so worrying about decimal places beyond that is pointless. — vacawama, Jun 21 '18 at 10:26
Makes good sense. I'll just go with the 'short' version then. Thanks, guys :) — ThomasTe, Jun 21 '18 at 10:28
By the way, do you know why the altitude keeps updating/changing, even when the device is standing still on a table? — ThomasTe, Jun 21 '18 at 10:38
@ThomasTe, I added an answer that summarizes all of the comments. It includes a link to an article in IEEE about Broadcom's new chips for more accurate GPS. It is unknown when Apple will use more accurate chips in the iPhone. — vacawama, Jun 21 '18 at 11:42

vacawama · Accepted Answer · 2018-06-21T11:26:46.583

You are seeing 37.787358900000001 instead of 37.7873589 because of the nature of representing floating point numbers in a computer.

That said, it is pointless to worry about decimal places beyond the 6th position because even changing the 9 to an 8 would result in a change of about 1 centimeter. The GPS system is currently accurate to about +/- 5 meters, and with new chips being deployed by Broadcom that can be reduced to about +/- 30 centimeters in the near future.

By the way, do you know why the altitude keeps updating/changing, even when the device is standing still on a table?

Altitude calculations are done by computing the distance to the visible GPS satellites which orbit the Earth every 12 hours. Since the satellites are constantly moving, and different satellites come into view, these calculations do tend to fluctuate. This article though a bit dated is enlightening.

Swift: Coordinates not accurate when using latitude/longitude

1 Answers1