Latitude and longitude coordinates are often presented in degree minute second (DMS) format, such as 39° 45' 30" (39 degrees, 45 minutes, 30 seconds). However, Surfer can only plot lat/long data when it is decimal degrees format (39.75833°). This should not be confused with displaying lat/long data in DMS format. Surfer can create a map from raw data in decimal degrees, and then you can change the display of the labels on the map to DMS format (How can I format my lat/long labels in Surfer in degrees/minutes/seconds?). 

To convert from DMS to decimal degrees (DD):

1.  Click File | Open in Worksheet. 
2. In the Open dialog, select your data file and click Open.
3. Click Data | Coordinate System | DMS to DD.
4. In the DMS to DD dialog, 
1. In the Source Columns section, choose the appropriate longitude column from the Longitude dropdown list and choose the appropriate latitude column from the Latitude dropdown list. 
2. Choose the formatting of your lat/long columns from the DMS format dropdown list.
3. In the Target Columns section, choose the desired output columns for the decimal degrees values to be written to. By default these are set to the first two empty columns in the worksheet.
4. Click OK to create two new columns with the decimal degrees lat/long values.