Change units of the map scale bar in Surfer

The scale bar for a map in is map units by default. This can be changed, but how to do so depends on whether the map is in linear units (e.g. meters or feet), or spherical units (e.g. lat/lon degrees). 

Linear units

You can display the scale in other units if the map units are linear (i.e. meters, feet, etc.). To do so:

1. Select the Map Scale object in the Contents window.
2. In the Properties window, click the Labels tab.
3. In the Units section, 
   
   • The Map units field is the units of the projection of your map. This cannot be changed manually, but changes if the coordinate system of the map changes.
   • The Scale bar units field is the displayed units of your Map Scale. You can change this to whatever you like.

This option is only available for maps with a non-spherical coordinate system assigned to them. This means unprojected maps or maps with lat/long coordinates cannot show an adjusted scale bar in this way. To set or change the coordinate system of a map, see here: Surfer Coordinate Systems Training Video. 

Spherical coordinates (e.g. lat/lon)

If the map has a lat/lon coordinate system, then the scale bar is in degrees by default. The easiest way to change the scale bar units is to change the coordinate system of the map to a linear system (e.g. UTM). If you want to see lat/lon values on your map, you can then add a graticule. However, if that isn't possible or if you want or need to use with lat/lon coordinates for your map, it is still possible to change the units of your scale bar.

Method 1:

You can manually change the units of the scale bar by calculating the equivalent distance in your desired units (meters, feet, etc.). To do this, you can use the attached ScaleConversion.xlsx Excel spreadsheet as a convenient conversion calculator.

Method 2:

Alternatively, after adding a scale bar to the map in Surfer, follow the steps below.

1. Select the Map, click on the Limits page in the Properties window, and make note of the yMin and yMax. 
2. Find the center latitude of the map with this formula: [(yMax-yMin)/2] + yMin. 
3. Take the cosine(degrees) of the latitude from step 2. 
4. Multiply the value from step 3 by the conversion factor for the units you want. Some common conversion factors are:
   • kilometers = 111.3215 
   • meters = 111300
   • miles = 69.172
   • feet = 365228
5. Divide your desired increment value by the value from step 4. 
6. Select the scale bar.
7. On the Labels page in the Properties window, set the Label increment to the increment value chosen in step 5, and set the Cycle spacing to the value calculated in step 5.

See the attached ScaleCoordinates.srf file for an example file, complete with the original scale bar and scale bars in all four converted units mentioned above (m, km, ft, mi).

Updated June, 2022