Understanding Accuracy of Coordinates Shown on our Maps
The more decimal places there are in a set of coordinates, the more precise the coordinates will be. The coordinates used for Blue Mountain Peak marker on a google map, for example, is:
18.046678562528196, -76.57916942986412
That is 14 decimals, which is extremely accurate. Many coordinates are quoted with 0-6 decimals. To understand the implications of this, take a look at the table below. The table shows the level of accuracy gained, or lost, based on the number of decimal places in the coordinates:
| Decimal Places | Degrees | Distance |
|---|---|---|
| 0 | 1.0 | 68.97 miles / 111 km |
| 1 | 0.1 | 6.89 miles / 11.1 km |
| 2 | 0.01 | 3641.732 ft / 1.11 km |
| 3 | 0.001 | 364.173 ft / 111 m |
| 4 | 0.0001 | 36.417 ft/ 11.1 m |
| 5 | 0.00001 | 3.641 ft / 1.11 m |
| 6 | 0.000001 | 4.37 inches / 111 mm |
| 7 | 0.0000001 | .437 inches / 11.1 mm |
| 8 | 0.00000001 | 0.0437 inches/ 1.11 mm |
Try the tool below to visualize the difference.
There is a significant difference in a coordinate when no decimal places are given compared to a coordinate with 5 decimal places. A difference of ~68 miles or 110 kilometers.
Does that mean it is wrong to use less decimal points? It depends on the usage.
The mapping apps on this site use two decimal places. That's an accuracy of within .6 of a mile or 1 kilometer. That is acceptable when describing the location of a mountain, but it would not be as acceptable when describing the location of a building.
A coordinate of 3-5 decimal places may be more appropriate, depending on the size of the building. A building could be as large as several city blocks, an airport terminal or the Pentagon for instance, while another may be a corner store of 150 sq ft. The smaller the object being mapped, the larger the number of decimal places required to pinpoint accuracy. In the example of the pentagon, many more decimal places would required to pin point an actual entrance.
IMPORTANT Note: We tend to show 2 decimal places on our pages, but we may use more behind the scenes to map the actual location. It all depends on what is being mapped.
Latitude: One decimal place in latitude represents approximately 111 kilometers (69 miles) at any point on Earth. This distance remains constant regardless of location.
Longitude: The distance represented by one decimal place in longitude varies depending on latitude. Closer to the equator, it's closer to 111 kilometers, but increases as you move towards the poles. For example, at 45° latitude, one decimal place in longitude is about 78 kilometers (48.5 miles).
The implication of this is that the distances in the table above may be slightly different depending on how close the location is to the equator. It's not a big difference, but should be noted.
The Lat/Lng of the Halfway Tree Clock Tower is:
18.010729601450148, -76.79743708180094
Try decreasing the decimal places and enter them into the fields below to see the impact on the map. The differences should become visible around 5 decimal places. The lower you go, the further the distance. Try removing all decimal points.
Don't forget the minus sign in the longtitude