View source for Diveatlas:Coordinates

Dive Atlas documents regions and locations. One of the most important pieces of information about a place is where it is. That's documented using GPS coordinates.

== Format ==

The tooling that Dive Atlas uses to generate maps and other location-related features accepts most common formats of coordinates. The preferred system is decimal degrees.

== Precision ==

<big>TLDR</big>

On Dive Atlas when you're referring to the location of a place using coordinates, be mindful of the number of decimal places you include. Use the table below as a guide. It's fine to copy the exact coordinates of a location from a digital map and simply trim the decimals until it matches the required precision.

=== Discussion ===

When using decimal degrees, the number of decimal places used has significance. Basically, more decimal places indicates to the reader or software that the location is known more precisely and/or that the exactness of the location is more important. It can also communicate the size of a place.

For example, London covers 1,738 km^2. Drop a pin anywhere in that area and you are still referencing London; not much precision is required here, so specifying the location of London with centimeter precision doesn't communicate anything.

However, if you're trying to state the location of a specific tree in a forest, you need to be quite accurate! A difference of a meter or two likely pinpoints a completely different tree than the one you wanted. In this case, more precision is necessary to accurately note the location.

Note that in both cases, the number of decimals gives some indication as to the size of the thing being located; more decimal places suggests an individual thing, less decimals a larger area.

{| class="wikitable"
|+ Degree precision versus length
! decimal<br>places !! decimal<br>degrees !! DMS !! Object that can be ''unambiguously'' recognized at this scale !! N/S or E/W<br /> at equator !! E/W at<br>23N/S !! E/W at<br>45N/S !! E/W at<br>67N/S
|-
! 0
| 1.0 || 1° 00′ 0″ || country or large region || 111&nbsp;km || 102&nbsp;km || 78.7&nbsp;km || 43.5&nbsp;km 
|-
! 1
| 0.1 || 0° 06′ 0″ || large city or district ||  11.1&nbsp;km || 10.2&nbsp;km || 7.87&nbsp;km || 4.35&nbsp;km 
|-
! 2
| 0.01 || 0° 00′ 36″ || town or village || 1.11&nbsp;km || 1.02&nbsp;km || 0.787&nbsp;km || 0.435&nbsp;km 
|-
! 3
| 0.001 || 0° 00′ 3.6″ || neighborhood, street || 111&nbsp;m || 102&nbsp;m || 78.7&nbsp;m || 43.5&nbsp;m
|-
!4
| 0.0001 || 0° 00′ 0.36″ || individual street, large buildings || 11.1&nbsp;m || 10.2&nbsp;m || 7.87&nbsp;m || 4.35&nbsp;m
|-
! 5
| 0.00001 || 0° 00′ 0.036″ || individual trees, houses || 1.11&nbsp;m || 1.02&nbsp;m || 0.787&nbsp;m || 0.435&nbsp;m 
|-
! 6
| 0.000001 || 0° 00′ 0.0036″ || individual humans || 111&nbsp;mm || 102&nbsp;mm || 78.7&nbsp;mm || 43.5&nbsp;mm 
|-
! 7
| 0.0000001 || 0° 00′ 0.00036″ || practical limit of commercial surveying || 11.1&nbsp;mm || 10.2&nbsp;mm || 7.87&nbsp;mm || 4.35&nbsp;mm 
|-
! 8
|style=white-space:nowrap | 0.00000001
|style=white-space:nowrap | 0° 00′ 0.000036″
| specialized surveying || 1.11&nbsp;mm || 1.02&nbsp;mm || 0.787&nbsp;mm || 0.435&nbsp;mm 
|}

See [[wikipedia:Decimal degrees#Precision]] for more information.