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.

What we do today:

1. I will demonstrate basic Surfer procedures to turn a data set into digital elevation models.  You are free to follow along and see if you get the same results.
2. You will download a different data set and turn those into a contour map and a surface model.

Before starting Surfer, you might 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" drive or (preferably!) your Flash (thumb) drive.

I will demonstrate Surfer functions using a data set different from that which you will be using for your assignment this week.  If you want to download and follow along using an assignment file, scroll down to Data Links.

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. I have organized them in their default positions for today, but not all data sets you encounter will be so organized.  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.  Caveat:  Surfer can use files too large to organize in 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.

There are several ways to interpolate values.  When data are less than or comparable in density to your calculated grid density, use kringing.  This is a statistical methods developed for sparse data.  Where data are much denser than your calculated grid, use nearest neighbor.  Kginging large, densely sampled data sets - like those you will use for today's assignment - takes a lot of time and will not yield better results than nearest neighbor. 

Dr. D. will demonstrate a few contour map options.  If you see something you thing should be changed add improved, double click it and look for a dialog window.

Note: for a color pallet you need to navigate to the Golden Software folder on your desktop's "C" drive.  You are not authorized to save to the "C" drive but can read files stored there.  This company name is an expression of its software prices.

Once you get a nice map started, Save your project.  If you do, and if later on you somehow ruin all of your work, you can 'open' the project and get what you had the last time you saved.  As before, never "save" after messing up, as you cannot recover once you overwrite your saved file with a new file consisting of garbage.  I would keep all files in a single folder on the thumb drive. 

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.  Scale allows you to change the vertical scale.  We usually do not change horizontal scales because that can distort a map.

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 can be 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.  This week's data are pretty robust, but that is not always the case.  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 (maximum and minimum of both X and Y) of the grid at even values slightly beyond the measurement limits, and set the node spacing to a nice even value.  As usual for maps, horizontal = X = positive east, vertical = Y = positive north.

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.

If you attach a Surfer map to an email message, the person on the other end might not be able to open it if the project includes a post map.  If that person does not have Surfer, Windows might try to reorganize the Surfer map, perhaps with disastrous results.  Always export your Surfer product as an image and attach that image to email.  Save your Surfer project on your Flash drive so that you can edit it if the need arises at a later dare.

Assignment: Data links for your projects:  Please download one of the following data sets.  Generate a contour map and a surface map.  Please flip a coin to select your file: flip once to decide between the first and second pair, than again to select from the pair that wins the first flip.  I hope to have some variety in the maps I will assess.  These are very large files, covering a large area, with densely spaced data points (about every 90 meters).  As before, these are .txt files so, in Explorer, I right click the link and 'Save Target' to my thumb drive.

Data Set 1
Data Set 2
Data Set 3
Data Set 4

Due by noon on Friday: a contour map, and, a surface plot. Each map must include your name and date due as labels, plus a label that briefly states a title and labeled axes.  Export each image and import them to a Word document. What you see is what you get.  Please attach to a Message (NOT email!) addressed to me in Blackboard.

Briefly tell me what you think you are looking at, and why you arrived at that conclusion.

Contour maps should (almost) always be viewed with north at the top.  I rotate surface maps until the screen shows the feature's most important attribute or clearest manifestation.  You must label axes to indicate east and north directions.

NEVER send a Surfer project file to another computer.  If the person on the other end does not have Surfer, his or her computer might do something interesting with the file and your friend will have to clear up the debris.  Even if the recipient has Surfer, the files used to make your map are on your flash drive, and without these files, the project usually fails to perform as you intend.  SEND EXPORTED IMAGES, NEVER SURFER PROJECT FILES.

Please note: these are very dense data sets, considering the area covered.  The elevation survey samples the Earth's surface on a roughly 90-meter grid.  Where my Surfer grid is less dense than the data, I use Nearest Neighbor rather than kriging.  If you construct and overlay a post map, you will see just how densely even if you use the smallest possible symbol.  There are, however, sometimes gaps  in    the       coverage  where terrain is rugged.  "Nearest neighbor" can yield some odd results where data gaps exist.  Use a post map to check for data gaps and point those areas out as part of your analysis.  Draw polygons to cover any areas lacking data.

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.  This is the chromadepth pallet in the samples folder, Golden Software folder.  Stop by my office and I'll lend you a pair of the magic Chromadepth^TM glasses so you can see your contour map in 3-D.

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.  Past versions of Surfer did not export high-quality .jpg images but .gif format images were quite acceptable.  Check your image before closing your project in case you need to make changes.  If your image looks fuzzy, not sharp, export your image again, using higher resolution settings.

Extra credit: Tell me what you see after making your maps.  What is the feature whose image you just constructed?  Import your images (contour map and surface map) to a Word document and write a paragraph describing the main feature or features of your particular landscape.  If you use Google Earth, check out the following locations to see if something there resembles the outcome of your product.  These are not necessarily in the same order as the data sets.

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.

Return to Syllabus

About your data: the 4 digital elevation data sets posted for your project (you are required to use only one) were obtained from http://srtm.usgs.gov/data/obtainingdata.html - Shuttle Radar Topography Mission.  Global terrain data are available for free download covering virtually all land areas on our favorite planet.  For most of the earth, data points are 3 arc-seconds (about 90 meters) apart.  Sample density is greater in much of the USA.  Data for Ohio and Michigan are spaced at 1 arc-second intervals, and data for selected areas are even denser than that.  Of course, greater data density means large files per unit area.  The 'graben' data set used for the demonstration are older and less detailed (larger distance between data points).