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How do I create a vector map in Surfer with magnitude and direction arrows at the data points?

You can create a map showing vectors either by:
  1. Creating a post map with a vector at each particular XY location using magnitude and direction data. The process will depend on if you already have the magnitude and direction data for the data points.
    1. You can have Surfer calculate the magnitude and direction data (requires you have Z data for each XY point).
    2. You already have the magnitude and direction data in a worksheet.
  2. Gridding the data and creating a vector map.

 

1.1. Post Map from XYZ data file, with Surfer calculating the magnitude and direction:

Calculate the direction and magnitude at each data point:

  1. If you do not already have a grid of the XYZ data for your points, click Home | Grid Data| Grid Data, select the data file and click Open.  Select the gridding parameters (or accept the defaults) and click OK in the Grid Data dialog to create the grid.
  2. Click Grids | Calculate | Calculus.
  3. In the Grid Calculus dialog, select the original grid from the Input Grid drop down list, or click Browse to select the original grid.
  4. Select Terrain Modeling | Terrain Slope. This will be the slope value or slope amount.
  5. If Add grid as a layer to is checked, uncheck the box.
  6. Click OK. This will create a grid file of the slope.
  7. Click Grids | Calculate | Calculus again.
  8. Select the original grid from the Input Grid drop down list, or click Browse to select the original grid.
  9. Select Terrain Modeling | Terrain Aspect. This will be the slope direction.
  10. If Add grid as a layer to is checked, uncheck the box.
  11. Click OK. This will create a grid file of the angle of the steepest slope.
  12. Click Grids Calculate | Point Sample.
  13. In the Point Sample dialog, set the Terrain Slope grid file as the Input Grid.
  14. Set the data file used to create the original grid as XY Data. This data file should have XY coordinates for each point where you want a vector. 
  15. In the Data Columns section, assign the X and Y columns from the data file to X and Y.
  16. Choose a column to store the Z values in. By default, Surfer chooses the first empty column.
  17. Click OK. A worksheet opens with the XY Data values and Z values for each XY point.
  18. Change the Grid Value column header to Slope Amount.
  19. Click File | Save and save the file.
  20. Click File | Close and close the file.
  21. Click Grids Calculate | Point Sample again.
  22. In the Point Sample dialog, set the Terrain Aspect grid file as the Input Grid.
  23. Set the data file saved in step 18 (with X, Y, and Slope Amount) as XY Data
  24. In the Data Columns section, assign the X and Y columns from the data file to X and Y.
  25. Choose a column to store the Z values in. By default, Surfer chooses the first empty column.
  26. Click OK
  27. Change the Grid Value column header to Slope Direction.
  28. Click File | Save and save the file.

 

Now you can create a post map to display the data:

  1. Click a plot tab, or click File | New | Plot Document
  2. Click Home | New Map | Post  (or Home | Add to Map | Layer | Post to add this to another map layer).
  3. Select the DAT file saved above and click Open.
  4. In the Contents window, click the Post layer.
  5. On the General page of the Properties window, specify the X coordinates and Y coordinates columns.
  6. Click the Symbol tab, and set the Angle column to be the column with the Slope Direction.
  7. Expand the Marker Properties section and change the Symbol to an arrow. You can keep the Symbol Set set to GSI Default Symbols and choose an arrow symbol (like symbol Number 62).
  8. In the Symbol Size section, set the Sizing method to be Proportional.
  9. Click the Scaling button.
  10. Set the Worksheeet Column Containing Height to the Slope Amount column. Change the Symbol Height values if you want, and click OK. The gradient vectors are shown at each data point location.

vector map

 

1.2. Post Map from XY data file with known magnitude and direction:

  1. Combine the magnitude and direction information into a single file with your XY point location coordinates.
  2. Create a post map with the Home | New Map | Post menu command, select your data file and click Open.
  3. Select the Post layer in the Contents window.
  4. In the Properties window, click on the Symbol tab.
  5. In the Symbol section, expand Marker Properties and select a Symbol Set and Symbol. Some recommended symbols include:
    1. GSI Default Symbols 60 and 61 plot the center of the arrow at that location. 
    2. GSI Default Symbols 62 and 63 plot the base of the arrow at the XY coordinate.
    3. For wind arrows, select the GSI Wind Barb Symbols set.
  6. In the Symbol Angle section, change the Angle column to the column containing the direction information.
    1. Note: Surfer measures the direction in a counter-clockwise direction, and you can use the worksheet to multiply the direction column by -1 to reverse the direction.
  7. In the Symbol Size section, change the Sizing method to Proportional.
  8. Click on the Scaling button.
  9. Set the Worksheeet Column Containing Height to the column containing the magnitude data. Change the Symbol Height values if you want and click OK.

 

2. Vector Map from GRD file:

Surfer can create vector plots from a grid file, or from two grid files individually containing direction and magnitude information.

The 1-grid vector map calculates the slope or gradient direction from the Z values in the GRD file to draw vectors with magnitude and direction properties. 

  1. Click Home | New Map | Specialty | 1-Grid Vector.
  2. Select the grid file and click Open. The vector map is created.

The 2-grid vector map draws vectors based on two grid files containing the X and Y components, or the magnitude and direction components. 

  1. Click Home | New Map | Specialty | 2-Grid Vector.
  2. Select the first grid file and click Open. This is the grid with the angle or direction component.
  3. Select the second grid file and click Open. This is the grid with the magnitude or length component. The vector map is created.

vector map

 

See also: How do I grid directional data, such as wind speed and direction, in Surfer?

 

Updated February 13, 2017

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