create your contour map

Creating Contour Maps with ArcGIS

Notes:

This tutorial was written for ArcGIS 9.3.  The layout in ArcGIS 10 is completely different so this tutorial will not help you.  This tutorial uses the “Horizontal” sheet in the “GIS_EM_Data.xls” file as an example.

Get the data at:  http://infohost.nmt.edu/~dbutler/ERTH325/

Opening ArcGIS:

We must first take care of some basic things.

1. Create a directory somewhere on your TCC account, the “U:” drive, to keep your GIS files in.  You will want to create a separate folder, in this main GIS folder, for each project (i.e. u/yourusername/Documents/GIS/ERTH325/EMLab).


2. Start > All > ArcGIS > ArcCatalog


3. Click File > Connect Folder


4. Select the GIS directory you just created and click “OK”.  Now you will be able to access this folder in ArcGIS.



5. Start > All > ArcGIS > ArcMap 

Enabling the “Spatial Analyst”:

To create contour maps in ArcGIS we need to use the “Spatial Analyst”, if you have not used ArcGIS on the TCC before it is not enabled.

1. Select “A new empty map” in the dialog box and click “OK”.


2. Tools > Extensions


3. In the main field, check the box next to “Spatial Analyst”, click “Close”.


4. Right-click somewhere on the top-menu bar.  This will open a large menu.  Scroll down to “Spatial Analyst” and click.  You have just opened the “Spatial Analyst” toolbar.  Go you.  You can dock the toolbar or leave it where it is, whatever you prefer.

Creating the Map:

We are now ready to create the map.

Setting Your Coordinate System:

(For this map this is not necessary but it is good to get into the habit of doing this.)

1.  Right-click on “Layers” in the box to the left.  Go to “Properties”, then the “Coordinate System” tab.


2. In the bottom box click Predefined > Projected Coordinate Systems > UTM > NAD 1927 > NAD 1927 UTM Zone 13N   Click “OK”.


Adding the Data:
3.  Tools > Add XY Data


4. Click the folder icon next to the top drop-down box; navigate to where your “GIS_EM_Data.xls” file is located.  Double click the excel file, select the “Horizontal” sheet, and click “Add”.


5. Click the “Edit” button in the bottom right-handish corner.  Click the “Select” button under the big blank box.


6. Navigate through the file system as follows:
Projected Coordinate Systems > UTM > NAD 1927 > NAD 1927 UTM Zone 13N.prj (This step adds a coordinate system to your data and is not strictly necessary, but it is good to get in the habit of doing this in case you ever take an actual GIS class.)


7. Click “Add”, then “OK”, then “OK”, then “OK”.  You have just added your data; you’re a regular GIS master.


8. Now in the left hand box you will see your data under “Layers”, it should say “Horizontal$ Events”, right-click it, then go to Data > Export Data.


9. Click the radio button next to “the data frame”, and then click the file icon next to the file path.  Navigate to your folder; re-name the file something that you’ll remember, click “Save”, click “OK”, click “Yes”.


10. Right-click on “Horizontal$ Events” under “Layers”.  Select “Remove”.


11. Time to save!  File > Save As…  Then navigate to your folder, name it something useful, click “Save.


Performing the Interpolation:
12. Go to your “Spatial Analyst” toolbar, click the “Spatial Analyst” drop-down, and click “Options”.


13. Under the “General” tab, in the “Analysis Coordinate System” box select the second option.


14. Under the “Extent” tab, in the “Analysis Extent:” drop-down select “Same as Layer “whatever you named it””.  Click “OK”.


15. Click on “Spatial Analyst” again.  Mouse over “Interpolate to Raster”, click “Inverse Distance Weighted”.  (It can sometimes be useful to play around with the different interpolations; however, for the sake of time this guide will only explain IDW.)


16. In the new dialog box, under “Input Points” select your layer if it is not already selected.  Under “Z Value Field” select “mS/m”.  Change the value in power to 4.  Click the folder icon in the bottom right-hand corner.  Navigate to your folder, save it as something useful, click “Save”, and click “OK”.  Oooooo pretty colors, you’ve completed your first ArcGIS interpolation, congratulations.


Adding the Contours:
17. Go to the “Spatial Analyst” tool bar.  Spatial Analyst > Surface Analysis > Contour


18. Under “Input surface:” select the raster you just created if it is not already selected.


19. Change the “Contour Interval:” to 10.


20. Click the bottom right-hand folder.  Navigate, useful name, “Save”, “OK”.  Yay, contour lines!


Make it pretty:
(This whole section is relative, this is just what I like, but it should be done or else your map won’t end up looking very good.)


21. Right-click on your interpolated raster.  Select “Properties” at the very bottom.


22. Select the “Symbology” tab, look for the button “Classify” (right-toppish), and click it.


23. Under the “Method” drop down in this new window, select “Defined Interval”, then change the “Interval Size:” to 10 (our contour interval), click “OK”, click “OK”.


24. As you can see, the colors now match up with the contours.  In theory you could use any multiple of your contour interval (within reason) and get a good result, but I like it when each contour has its own color.


25. Now we will change the color scheme, mostly because I don’t like the default.  Right-click on the interpolation layer, click “Properties”, go to the “Symbology” tab.  You change the color scheme by selecting a “Color Ramp:” (the big rectangle of color in the middle of the window).  You can pick one you think will look good by clicking it in the drop-down and then clicking “Apply”, drag the window out of the way and see what you have.  You can also right-click on the color ramp box and uncheck “Graphic View” to get all of the ramp names.  It just takes trial and error to find one you like.  You can always go back to the original which is called “Surface”.


Setting up the Map Layout:
(This whole section is relative, this is just what I like, but it needs to be done, the layout can be tweaked to suit your own preferences, experiment.)


26. Now we will set up the map layout.  First click the little icon that looks like two windows with an arrow above them, if you mouse over it, it will say “Change Layout”.


27. Under the “General” tab, select “LetterLandscape.mxt” and click “Finish”.


28. You are now in “Layout View”.  Drag the legend, the compass rose, the scale bar, and the smaller text box out of the way.  Move the map title (larger) text box to the top of the map.  Take this time to name your map something informative and to the point. (Double click the text box, type, click “OK”).


29. Get rid of any excess white space in the map box, by shrinking the window.  Move it to once side of the map, to leave room for your legend.


30. Now move your legend into the open space, also place your compass rose somewhere on the map at this time, and move the smaller text box back onto the map.  Take this time to put useful information into this smaller text box.  Let’s put the contour interval in it.  Double click the text box, type something along the lines of “Contour Interval 10 mS/m”.


31. Double click on your legend.  Under the “Legend Items:” box click on your contour layer and then click on the single arrow pointing to the other box.  Now double click on your interpolation layer and select the option third down in the first column, click “OK”, click “OK”.


32. Your legend is looking better almost done with it.  We need to rename the layers to make them useful on a legend.  Click on the point data layer once, wait, then click once again.  Name your point data something legendy like “Measurement Location”.  Do the same with your interpolation layer, you may want to also include units.


33. Now we need to either format your scale bar or add grid lines.  Step 34 details formatting the scale bar.  Step 35 details adding grid lines.


34. Double click the scale bar.  Under the “Format” tab, click the “Style” drop-down; select “Double Alternating Scale Bar 1” (I like this one so we’re using it).  Under the “Scale and Units” tab change the “Number of divisions” to 2, the “Number of subdivisions” to 2, and change the “Division Units” to meters.  Under the “Numbers and Marks” tab change the “Position” to “Below bar”.  Click “OK”.  Move the scale bar somewhere useful.


35. View > Data Frame Properties…  Under the “Grids” tab click “New Grid”.  Select “Measured Grid”, click “Next”.  Select “Labels only”, change the X and Y interval to 10, click “Next”.  Click “Next”, click “Finish”.  Now click “Properties” in the first dialog, under “Intervals” select “Define your own origin:” enter 0 and 0.  Click “OK”, click “OK”.


Exporting your Map:
36. File > Export Map


37. Navigate to your folder.  Change the save type to whatever you like, I prefer using PNG images for maps.  Make sure you save it as a decent size and quality.  Click “Save”.


38. Save your overall map.


39. You’re done, GIS contour map accomplished, give yourself a pat on the back.