There are times when you may need to change the coordinate system of the grid file itself, instead of just a map, for use in Surfer. This may be the case when performing grid operations such as Grid Volume or Grid Calculus or when working with 3D surface maps.
Grid Volume and Calculus commands require linear X, Y, and Z units in order to provide meaningful results. For example, a grid file with Z values in feet and XY coordinates in Lat/Lon will result in a very small volume with the units lat degrees * long degrees * feet. Similarly, slope analysis of Lat/Lon can result in all slopes being near 90°.
3D surface maps do not support coordinate systems and therefore require the same coordinate system for all grids and files used to create each map layer.
To convert a grid to a new coordinate system in Surfer, follow the steps below.
- Click Grids | Edit | Project.
- In the Grid Project dialog, click Browse, select your grid file, and click Open.
- Click Set in the Input Grid section.
- In the Assign Coordinate System dialog, select the coordinate system of the original data and click OK.
- Click Set in the Output Grid section.
- In the Assign Coordinate System dialog, select the coordinate system you want the grid converted to and click OK.
- Click OK in the Grid Project dialog to create the new grid file.
In Surfer 13 and earlier versions, there is not a direct way to convert the grid file from latitude and longitude coordinates to a system whose native unit is feet or meters; however you can use the Surfer worksheet for this task:
- First identify the Z data unit. If the Z units are meters, then the lat/long coordinates can be converted to meters also (e.g. UTM). If feet, you can convert to a system where the units are in feet (e.g. State Plane in the US).
- Click Grid | Convert, select the grid file and click Open.
- Choose to save the grid in an DAT XYZ (*dat) file format and click Save.
- Click File | Open, select the DAT file and click Open. It will open in the Surfer worksheet.
- Click Data | New Projected Coordinates.
- Set the source data columns, X: Column A and Y: Column B.
- Click the (...) button under Source Coordinate Systems.
- In the Assign Coordinate System dialog expand Predefined | Geographic (lat/lon), and select the appropriate datum for the data. The most common datum for lat/long coordinates is World Geodetic System 1984.
- Click OK.
- Click the (...) button under Target Coordinate Systems.
- In the Assign Coordinate System dialog change the coordinate system to either UTM or State Plane 1983 under Projected Systems. Here you will need to either know the UTM zone or the State Plane zone.
- Click OK.
- Click OK and the coordinates are converted into the target columns.
- Click File | Save and File | Close.
- Click Grid | Data, select the data file and click Open. In the Grid Data dialog:
- Make sure the X and Y column are set to the new columns of meters or feet.
- Select the Nearest Neighbor gridding method.
- Use the same grid resolution (same # of Nodes) as the original grid file.
- Click OK and the new grid is created. Use this grid for volume calculations or for whatever other purpose you wish.
Updated October 31, 2018
Comments
2 comments
Grids | Edit | Project.
Is this feature built into automation?
I want to convert coordinates without changing the grid.
This command is not yet built into automation, but I have added your vote to our suggestion file for this feature to be added. Should we add it to future versions we will let you know!
Thank you for your feedback, we greatly appreciate it!
Thanks,
Brittany
Golden Software
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