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Convert GPS Coordinates for Marine Navigation and Boating
Easily convert between Decimal Degrees (DD), Degrees Minutes Seconds (DMS), and Degrees Decimal Minutes (DDM) coordinate formats with our free online converter tool. Perfect for boaters, sailors, navigators, and outdoor enthusiasts who need to transfer waypoints between different navigation systems and marine GPS devices.
Why Convert Coordinate Formats?
Different navigation systems and charts use different coordinate formats:
- Modern digital maps and GPS apps typically use Decimal Degrees (DD)
- Traditional nautical charts often use Degrees Minutes Seconds (DMS)
- Marine GPS units and chartplotters commonly use Degrees Decimal Minutes (DDM)
Converting between these formats allows you to accurately transfer waypoints between different navigation systems, paper charts, and digital devices.
Coordinate Format Guide
Decimal Degrees (DD)
Format Example: 37.7749, -122.4194
- Simple decimal format used by Google Maps, digital charts, and many GPS applications
- Latitude ranges from -90° (South) to 90° (North)
- Longitude ranges from -180° (West) to 180° (East)
- Negative values indicate South latitude or West longitude
Degrees Minutes Seconds (DMS)
Format Example: 37° 46' 29.64" N, 122° 25' 9.84" W
- Traditional format found on many nautical charts and maps
- Uses degrees (°), minutes ('), and seconds (") with a direction (N/S for latitude, E/W for longitude)
- 1 degree = 60 minutes, 1 minute = 60 seconds
- Common in traditional navigation and cartography
Degrees Decimal Minutes (DDM)
Format Example: 37° 46.494' N, 122° 25.164' W
- Hybrid format used by many marine GPS units and chartplotters
- Combines whole degrees with decimal minutes
- Popular in marine navigation systems like Garmin, Raymarine, and Furuno
- Balances precision and readability for practical navigation
How to Convert Between Coordinate Formats
Converting DD to DMS (Decimal Degrees to Degrees Minutes Seconds)
- For the degrees: Take the whole number portion of the decimal degrees
- For the minutes: Multiply the decimal portion by 60 and take the whole number
- For the seconds: Take the remaining decimal from step 2, multiply by 60
- For the direction: Use N for positive latitude, S for negative latitude, E for positive longitude, W for negative longitude
Example: Converting 37.7749° to DMS
- Degrees: 37°
- Minutes: 0.7749 × 60 = 46.494 → 46'
- Seconds: 0.494 × 60 = 29.64"
- Direction: N (positive latitude)
- Result: 37° 46' 29.64" N
Converting DD to DDM (Decimal Degrees to Degrees Decimal Minutes)
- For the degrees: Take the whole number portion of the decimal degrees
- For the decimal minutes: Multiply the decimal portion by 60
- For the direction: Use N for positive latitude, S for negative latitude, E for positive longitude, W for negative longitude
Example: Converting 37.7749° to DDM
- Degrees: 37°
- Decimal Minutes: 0.7749 × 60 = 46.494'
- Direction: N (positive latitude)
- Result: 37° 46.494' N
Converting DMS to DD (Degrees Minutes Seconds to Decimal Degrees)
- Calculate decimal degrees: Degrees + (Minutes/60) + (Seconds/3600)
- Apply direction sign: If South latitude or West longitude, make the result negative
Example: Converting 37° 46' 29.64" N to DD
- Decimal calculation: 37 + (46/60) + (29.64/3600) = 37.7749°
- Direction: N (positive latitude)
- Result: 37.7749°
Converting DDM to DD (Degrees Decimal Minutes to Decimal Degrees)
- Calculate decimal degrees: Degrees + (Decimal Minutes/60)
- Apply direction sign: If South latitude or West longitude, make the result negative
Example: Converting 37° 46.494' N to DD
- Decimal calculation: 37 + (46.494/60) = 37.7749°
- Direction: N (positive latitude)
- Result: 37.7749°
Converting DMS to DDM (Degrees Minutes Seconds to Degrees Decimal Minutes)
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- Keep the degrees the same
- Calculate decimal minutes: Minutes + (Seconds/60)
- Keep the same direction
Example: Converting 37° 46' 29.64" N to DDM
- Degrees: 37°
- Decimal Minutes: 46 + (29.64/60) = 46.494'
- Direction: N
- Result: 37° 46.494' N
Converting DDM to DMS (Degrees Decimal Minutes to Degrees Minutes Seconds)
- Keep the degrees the same
- For minutes: Take the whole number portion of the decimal minutes
- For seconds: Multiply the decimal portion of the minutes by 60
- Keep the same direction
Example: Converting 37° 46.494' N to DMS
- Degrees: 37°
- Minutes: 46'
- Seconds: 0.494 × 60 = 29.64"
- Direction: N
- Result: 37° 46' 29.64" N
Common Uses for Coordinate Format Conversion
- Transferring waypoints between different navigation systems
- Plotting positions from digital maps onto paper charts
- Entering coordinates from paper charts into GPS devices
- Sharing locations between different navigation apps and devices
- Recording fishing spots, dive sites, or anchorages in a consistent format
- Converting coordinates from cruising guides to your preferred format
- Navigating to locations shared by other boaters or in online forums
Tips for Accurate Coordinate Conversion
- Always double-check your conversions, especially for critical navigation
- Pay attention to the direction (N/S/E/W) when converting
- Remember that West longitude and South latitude are negative in decimal degrees
- For navigation safety, verify converted coordinates on a chart before use
- Consider rounding to an appropriate precision for your navigation needs
- Always maintain a backup navigation method when relying on converted coordinates
Use our free coordinate converter tool to quickly and accurately transform waypoints between DD, DMS, and DDM formats for all your marine navigation and boating needs.