Convert DMS and decimal degree coordinates for field use
A coordinate can be correct but interpreted in the wrong format. DMS versus decimal degrees is a common field mistake.
Field takeaways
- DMS uses degrees, minutes and seconds.
- Decimal degrees use one number for latitude and longitude.
- Comma, decimal separator and direction letters can cause errors.
- KML and map sharing commonly use WGS84 lat lon.
- MapLab Survey helps keep coordinate format context.
Two notations, one coordinate
DMS writes a coordinate as degrees, minutes and seconds; decimal degrees pack the same information into a single number. The classic mistake is reading 41°30' as 41.30 degrees: thirty minutes is half a degree, so the correct value is 41.5, and the difference on the ground is almost a kilometre. This single conversion is where field positions are lost most often.
Signs and letters
N and E are positive, S and W negative. A lost sign flips the hemisphere and puts the point on another continent. With hand-typed values, also check whether the decimal separator is a dot or a comma — when both notations meet in one table, the numbers break silently.
What to check in the field
- Is the value latitude-longitude, or a UTM/TM coordinate in metres?
- Dot or comma as the decimal separator?
- Are the N and E directions right?
- Has the latitude-longitude order been swapped?
- Is the source stated as WGS84, ED50 or TUREF?
Keep the decimals
Every decimal place you drop moves the point on the ground. Copy the full value, especially if you intend to navigate to it. Two coordinates that are "roughly the same" are two different places in the field.
Display before you commit
Note the format and source before adding the coordinate to the project, then display the point on the map and confirm it falls in the expected area. That visual check takes seconds and catches the sign and order errors a table of numbers never reveals. If a point appears far from where it should, look at the format and the coordinate order first — not at the GPS.
Try these steps on your own phone.
MapLab Survey handles RTK/GNSS point capture, drawing, area and volume calculations and coordinate conversion, then exports to DXF, KML/KMZ, GeoJSON, Shapefile, GeoPackage, NCZ or CSV. Capture, calculation and export work offline. Live NTRIP corrections and online basemaps need a connection.
Frequently asked questions
What is DMS?
Degrees, minutes and seconds coordinate format.
What are decimal degrees?
Latitude and longitude as decimal numbers.
Why does a point go to the wrong place?
Format, order, datum or decimal separator may be wrong.
What does KML use?
Commonly WGS84 latitude and longitude.
Technical references
The field guidance in this article is aligned with the technical and official references below.
Related: Lat lon to UTM · Google Maps coordinates · Coordinate conversion app · MapLab Survey