Trival pursuit:  One member of this class asked about the person whose image was used as background for last week's instructions.  Who can answer his question?  I can, of course, but that's no fun.

Objective: introduce students to basic Surfer operations so that students can generate contour maps and surface plots from text file containing spatially variable numerical data from field project.

Before starting Surfer, you need a registration number.  Write down your number (click here for Table) so you can enter it when asked by Surfer.

About your data: today you are working with digital topography. The ASCII file can be accessed via  this  link.  Right click the link and save this file (as .txt!) to your "H", "C" or Flash drive.

I recommend you set up a folder on your Flash drive to keep all Surfer-related files, and begin by saving these data to that location.  This will become the default location for all further Surfer files.

Data organization: there are 3 columns of numbers. They are: "X" coordinate and "Y" coordinates (in kilometers, east and north respectively), and elevation in meters.  The instructor has organized this file with Surfer in mind, something you should now be able to do with your own data with the help of Excel.

Getting started: before making a contour map, you must generate a grid of values. GRID then DATA opens a dialog window. Browse your "H" (or wherever you saved the data) drive until you see the graben.txt file among your choices. Click that file and OK.

For the first run, we will accept defaults. Simply click "OK" and a grid will be generated. After the grid is calculated, click MAP then CONTOUR. The default input should be graben.grd - click OK and the map should appear. Commands VIEW then FIT TO WINDOW allows you to see the map up close.

Dr. D. will demonstrate a few contour map options.

Do you want to see a surface plot? Click Map then Surface - OK - and you now have a surface plot in addition to a contour map. To view them separately, click and drag them apart. To rotate the surface plot, select it, the select View in the dialog box - you can now rotate the perspective with respect to vertical and horizontal position.

Post maps: where are the data points? Click Map - Post - select graben.txt - OK - and you get a map with "+" marks at each location where a measurement was made. Symbols too large? Double click the post map and look for the Size box - use the down arrow to shrink the symbols. 

Post maps are very important.  They show the reader where observations upon which a contour map was constructed are located.  The wise person does not interpret contours that are poorly constrained by observations.  The wise person learns to recognize bad data and never shows maps containing likely errors to the client, thesis advisor or editor.  More on this next week.

Overlaying maps: click the post map, hold down the Shift key as you click the contour map. Black squares should surround both maps - they are both 'selected' - then click Map - Overlay Maps. Can't see the data point symbols? Click Map - Edit Overlays -Post -Move to Front.

Format and label axes by double clicking - the dialog box appears similar to some seen in Excel. Change contour intervals by double clicking the center of the contour map. If you like colors, double click a box under "Fill" - after you have placed an "X" in the "Fill Contours" box (by clicking it).  There are a number of pallets saved in the Golden Software folder

To get rid of a map, click on the map and then hit the "Delete" key. Edit - Undo can sometimes recover a map you have just messed up, if you 'undo' immediately.

The toolbar on the left includes and arrow (select item), T (for text - titles and labels), various "draw" items (polygon, line, symbol, rectangle, oval, ellipse, - and magnifying/inverse magnify icons. --------------------------------------------------------------------------------------------------------------------

Now that you have seen the basic commands, let's go back to "Grid - Data", use the edited data file, and take control from the defaults.

Set limits of the grid at even values slightly beyond the measurement limits.

Set the grid interval such that the grid is spaced with "X" intervals equal to "Y" intervals. Set a grid with points more frequent than the average data spacing but, in general, do not place more than 2 grid points between observation points. When I have data at a 1 kilometer spacing, I usually set the grid at 0.5 kilometer.

Note: when you save a map that includes a post map, the file from which the post map was drawn must be available when you "open" that map in the future. I save all data dealing with a project on the same disk, in the same folder, so that all information needed to open and revise maps is available when needed. 

If you see something you think should be prettier, double click it and see what you get in the way of a dialog box.  Get rid of unneeded zeros (Format numbers - axis labels and contour line labels).  Select a font that makes numbers easy to read.

Due by noon on Monday, February 7: contour map with data points posted, and, a surface plot. Each map must include your name and date due as labels, plus a label that briefly states a title (this is the Comayagua Valley, Honduras) and labeled axes. What you see is what you get - make certain that the map is pretty before printing a copy - and remember that the printer is black & white only.

Exporting color images: I doubt many of you have a copy of Surfer 8 on your home computers. You can "Export" a colored map as an image and insert it into a Word document - or just print it out with your home computer.  Make certain that the exported map has aspect ration (vertical and horizontal relative dimensions) preserved.

Also, Surfer does not export nice .jpg files of complex, detailed maps (the software company was too cheap to include a decent .jpg conversion) but the .gif images have always looked good to me.  I recommend you export as a .gif, then use image processing software (future topic) if you really need a .jpg image.  You are free to select your own image format if you are experienced in digital images and prefer another format, so long as the results are good.

NEXT TIME: We will learn to deal with multiple "z" values; blanking files for eliminating contours from those parts of a map where observations are lacking; blanking files for having Surfer write a file from which you can have a profile drawn and values saved in a file for plotting.

For extra credit, fill contours with appropriate colors and export an image of your final map, attach the result to e-mail and send it to me.  Color convention: very dark blue for lowest value, bright red for highest value, with spectrum going blue - green - yellow - orange - red.  

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