1. Read latitude, then longitude
A standard coordinate pair is written as latitude, longitude. Latitude measures north or south of the equator and ranges from 90° S to 90° N. Longitude measures east or west of the prime meridian and ranges from 180° W to 180° E.
- First number: latitude
- 40.7128
- Positive means north of the equator.
- Second number: longitude
- -74.0060
- Negative means west of the prime meridian.
Quick check: a latitude can never exceed 90. If the first number is 120, the pair is probably written longitude first.
2. Recognize the three coordinate formats
These examples all point to the same location in New York City. Only the notation changes.
- Decimal degrees (DD)40.7128, -74.0060Commonly used for: Map apps, websites, and data files.
- Degrees and decimal minutes (DM)40° 42.768′ N, 74° 0.360′ WCommonly used for: Marine navigation and some GPS devices.
- Degrees, minutes, seconds (DMS)40° 42′ 46″ N, 74° 0′ 22″ WCommonly used for: Printed maps, surveying, and traditional notation.
3. Translate signs and compass directions
Decimal coordinates usually use positive and negative signs. DM and DMS usually use the letters N, S, E, and W. They express the same direction rules:
| Direction | Decimal sign | Example |
|---|---|---|
| North | Positive | 40.7128 |
| South | Negative | -33.8688 |
| East | Positive | 151.2093 |
| West | Negative | -74.0060 |
Do not combine a negative sign with S or W. Write either -74.0060 or 74.0060° W, not both.
How to write GPS coordinates correctly
- Put latitude first and longitude second, separated by a comma.
- Use one format consistently; do not mix decimal degrees with DMS.
- Include either signs or compass letters so the hemisphere is clear.
- Keep enough precision: five decimal places in DD is about one meter.
Common mistakes to avoid
- Reversing the orderMost tools expect latitude, longitude. Confirm the expected order before pasting into GIS software.
- Dropping a minus signChanging -74.0060 to 74.0060 moves the point from west of Greenwich to east of it.
- Treating minutes as decimals40° 30′ is 40.5°, not 40.30°, because one degree contains 60 minutes.
Before you share a pair, open it in a map and make sure the pin lands where you expect.