Creating Topographic Profiles using GRAPHER and SURFER

We did a number of exercises using SURFER for contour, base, image and post maps. GRAPHER interfaces with SURFER nicely, especially if you want to plot profiles chosen from your SURFER grids. Plotting a topographic profile from one of the DEMs you worked with provided a good example. Here are the steps to produce a profile from a grid (any grid works, not just the DEMs in the example):

To create a profile line in SURFER

• Create a contour or image map on one of your DEMs; click on it.
• Select Digitize from the Map Menu
• Click the starting and end points of a desired profile across the map and the DIGIT.DAT window pops up and records the points as you click them. So, click a few points along a curve.
• Save the file using Save as Type: Boundary Files (*.bln) by providing an appropriate name, such as SLICE, and letting SURFER add the .bln file extension. Thus what gets saved is Sliced.bln.
• Close the file
• Turn off Digitize in SURFER’s Map Menu.

To plot the profile line on the map in SURFER:

• Simply load SLICE.BLN as a base map
• Right click on the base map to change the line properties (color, style).
• Hit F2 or Edit All from the Edit Menu
• Select Overlay Maps from the Map Menu
  

You could also use this technique to add outcrops of particular rocks, highlight areas, mark zones of contamination or whatever on your maps.

To create profile data for GRAPHER:

• Select Slice from SURFER’s Grid Menu
• specify the grid name you want a slice from (your DEM in this case)
• specify the blanking file (SLICE.BLN in my example)
• specify the OUTPUT DAT FILE, here, you get two choices:

  1. The first choice is: Output BLN File. This approach results in a file with three columns, X, Y, Z. The first row of the file will have the number of points in the first column and a "1" in the second column. If you want to post these data on your map you'll need to remove the first row.

  2. The second choice is: Output DAT File. This file will have five columns, X, Y, Z, Distance along the profile (sqrt(x^2 + y^2), and boundary number which SURFER uses if there is more than one boundary per file.

• click OK and SURFER writes the file (or files) you specified.

Plotting the profile in GRAPHER

Start GRAPHER

• select Line or Symbol from the Graph/New Graph Menu
• scroll through the subdirectory lists until you get to where you saved your file SLICED.DAT and double click (select) your data file. GRAPHER presents its LINE/SYMBOL PLOT parameter box as in the figure.
• select the appropriate column for the X values (A is east, B is north, C is Z, D is distance from the start for the DEM data)
• select the appropriate column for the Y values (column C to get Z values for the case at hand)
• you can modify the line and symbol parameters by double clicking on them in the LINE PLOT parameter box
• after you set the X, Y and line parameters for Curve 1 click OK and GRAPHER plots your graph.

Setting or Changing Plot Parameters in GRAPHER

Once you have your plot on the screen in GRAPHER it is easy to add additional data or change the parameters of the lines, symbols, axes and such. Basically all you need to do is double click on whatever item you wish to change. For example double clicking on the data on the graph brings the LINE PLOT Edit Box back onto the screen. From there you can add a line, change symbols, colors and the like. Double click on the X axis and you can add a title, change the scale, add/remove ticks, etc.

Fitting equations to your data

GRAPHER provides a really quick way to fit various functions to your data. When you brought up the LINE PLOT Edit Box by double clicking the data on the graph one of the tab options in that box was FITS… Fits provides eight choices for fitting functions to your data:

1. Linear
2. Log
3. Exponential
4. Power
5. Spline smoothing
6. Polynomial
7. Orthogonal polynomial
8. Linear through the origin
9. Running average.
   

All these methods are well-described in GRAPHER’s help file. Using additional options in the FITS Edit Box you can preview the fit, copy the statistics to Window’s clipboard and change the way the fit is displayed on your graph.

Exercises:

1. Plot two topographic profiles from one of the DEMs you used in a previous exercise.

• Make one profile with no vertical exaggeration, the other with enough vertical exaggeration to highlight the topography.
• Experiment with changing line and axis parameters.
• Add a title.
• Make it look good.

2. Add a Running Average fit to the graph from the previous exercise using a different color to display a smoothed representation of topography on the plot with vertical exaggeration.

3. Turn it in - one page, shades of gray.