If you have Surfer 14 or 15 and you have an image you want to georeference in Surfer, but you don't have the coordinates for the bottom left and top right corners, you can use internal points to calibrate the image. Instructions for doing so can be found here.
If you have Surfer 13 or an older version, and you have an image that you want to georeference, but you don't have the coordinates for the bottom left and top right corners, you can use internal points and an Excel spreadsheet to calculate the corner coordinates and georeference the image.
With the common use of Google Earth, it is easy to download aerial image of a site or location that you are interested in. From Google Earth you can save an image in an unreferenced image format. However, these maps are of little use if you cannot add Map objects in their correct location in Surfer. In order to display Map objects in their correct locations, the image will need to be georeferenced to a real-world coordinate system.
I will describe to how to georeference the image of Washington D.C., shown below, using Surfer and Google Earth.
For this example, I have used Google Earth to find locations of two prominent monuments in Washington, D.C. I will use these locations to georeference the above image. The two buildings that I chose to use in this example are the U.S. Capitol Building and the White House.
Below is a screenshot of the Google Earth view with pins placed at four monument locations.
Once you are ready to georeference an image, you can follow these steps:
- In Google Earth, get the coordinates of two interior points on the image. Mark them with pins, take a screenshot of the image, and record the latitude and longitude (in decimal degrees) in cells B4-B5 and C4-C5 of the attached spreadsheet: CalibratingImageCorners.xlsx.
- In Surfer, go to Map | New | Base Map. Select your image and click Open. The X and Y Axis objects will display with the image pixel coordinates.
- In the Object Manager, click on the Base object and then hover your mouse over Point 1. Take a screenshot of Surfer or record the X and Y values in cells C13-C14 of CalibratingImageCorners.xlsx.
- Repeat step 3 for Point 2 and enter the X and Y values in cells C15-C16 of CalibratingImageCorners.xlsx.
- With Base selected in the Object Manager, go to the General tab in the Property Manager. Record the xMax, yMax, xMin, and yMin as cells C18-21 in the spreadsheet.
- The map coordinates listed in cells C23-C26 will automatically calculate
- From the Property Manager | General tab, update the Image Coordinates in the Base object by typing the values from cells C23-C26 into the appropriate row: xMin, yMax, xMin, and yMin.
Once you have added the updated Image Coordinates, you have successfully georeferenced your image in Surfer. You can do this without knowing the coordinates of the image corners and with only two known locations within the image itself! You can see in the image below that the X and Y Axes are now updated with appropriate latitude and longitude coordinates.
If you would like to display other objects on the map with their latitude/longitude locations, you can now do this using a Post map or other map object. Click Map | Add | Post Layer command to create a Post map. Below is an example Post map made using the georeferenced base map image and the latitude/longitude points that were used for georeferencing.
The ability to georeference imagery in Surfer is just one of its many features! If you would like to know more about the capabilities of Surfer, please visit the product website: http://www.goldensoftware.com/products/surfer.
If you would like more advanced georeferencing features, I would recommend upgrading to Surfer 14 or using another Golden Software product, Didger 5. All the advanced georeferencing, digitizing, coordinate conversion, and mapping features you need in a low-cost, unbelievably versatile program. You can find more information about Didger on the product website: http://www.goldensoftware.com/products/didger.
Updated November 3, 2017