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When I overlay two maps in Surfer, they either disappear or are not overlaid correctly

If two maps are overlaid and one or both disappear, or are overlaid incorrectly, this may be a result of the maps being in different coordinate systems (i.e. one map in lat/long and the other map in UTM, or one map in inches and the other map in feet).

 

Before you overlay the maps, look at the X and Y coordinates of both maps. If the X and Y coordinates appear to be vastly different, then if you overlay them without previously specifying the coordinate systems, the points/map objects will either be on opposite ends of the map, or one or both maps may be so small that it looks like they disappear.

 

If the units of the grids are in a geographical or projected coordinate system, you can specify the coordinate system for each of the layers and then overlay them. To do this, follow these steps:

  1. In the Contents window select the first layer (i.e. Contours).
  2. In the Properties window click the Coordinate System tab. 
  3. If the coordinate system is not properly set, click Set next to Coordinate System.
    1. In the Assign Coordinate System dialog, select the appropriate coordinate system.
    2. Click OK.
  4. In the Contents window select the second layer in the second map.
  5. In the Properties window click the Coordinate System tab.
  6. If the coordinate system is not properly set, click Set next to Coordinate System.
    1. In the Assign Coordinate System dialog, select the appropriate coordinate system.
    2. Click OK.
  7. Now that the coordinate systems for both layers are assigned, you can select the maps and click Map Tools | Map Tools | Overlay Maps.
  8. To specify the coordinate system for the map to be displayed in, select Map in the Contents window.
  9. In the Properties window, click the Coordinate System tab.
  10. Click Change next to Coordinate System.
    1. In the Assign Coordinate System dialog, select the appropriate coordinate system.This is the coordinate system you want the map to be displayed in.
    2. Click OK. Both layers are converted into the coordinate system of the map, and displayed in that coordinate system.

 

If the units of the grids are not in a geographic or projected coordinate system, but the units are not equal, you must convert the units of one grid file into the units of the other grid file. If there is a linear transformation, you can use the Grids | Calculate | Transform command with the Scale option to convert the XY coordinates of one grid to match the units of the other. For example, to convert a grid from XYs in meters to XYs in feet, set the X Scale and Y Scale to 3.2808 to multiply the X and Y values by 3.2808. Click OK and the new grid in feet is created.

 

Updated February 8, 2017

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