CS 128/ES 228 - Introduction to Geographic Information Systems

Lab 2: Layers

Goals:

        By the conclusion of this lab period, you will have:

  1. Learned about simple file manipulation in the ArcMap software suite; in particular used ArcCatalog to help add data to a GIS.

  2. Explored the layering features of ArcMap.

  3. Become somewhat familiar with ShapeFiles and the data they contain.

Time Management Hint

As part of Step 6, you will be asked to gather a small amount of data using a GPS unit. There are several lab groups and only one unit. Obviously you cannot all do this simultaneously. You must have this data to complete Step 6, but there is no reason why you could not gather this data much earlier in lab. We recommend that each group take a moment when the other groups are not using the unit to read Step 6 and then go outside and gather the required.

 

Using the Table of Contents

  1. Helping ArcMap find its data.  ArcMap doesn’t store all the data used in a given GIS project within the project itself.  Instead, it stores links to the locations of the data.  These links are easily broken when the project or data files are moved from one folder or machine to another.  You can tell a data link is broken if ArcMap shows a layer in gray, with a red exclamation point, in the Table of Contents at the left side of the display, and the associated layer won’t display.
                Start ArcMap on one of the lab computers and open the supplied data set.  (It is similar, but not identical, to the one you used last week.)  If (as we intended) there are broken data links, right-click on the layer(s) and reestablish the correct source location for the data.  Note:  often once you fix one link, ArcMap will correct others in the same folder, but sometimes you have to fix each one individually.

  2. Editing the Table of Contents.   The table of contents of the Lab 2 GIS contains several layers.  What are they?  You can change the order of the layers.  How?   What happens if you put the aerial photographs in the top layer?  Use ArcMap to adjust the transparency of layers.  (Try the Effects toolbar - accessed through the View menu.)  Describe the affect of making a top-layer photograph semi-transparent.  Finally, reset the transparency of the photos and put them in the bottom layer.  Does it matter in which order the individual aerial photos are placed in the Table of Contents?  Why or why not?  

  3. Grouping layers.  The Table of Contents consists of a hierarchy with three levels.  The largest is the Data Frame which holds all the layers that are displayed on one map.  Data frames are symbolized by a stack of yellow pages.  What is the name of the data frame you are using?  Change the name to "Olean Quadrangle".  The next hierarchical level is the Group.  Add a new group called "Roads".  (Right clicking on the data frame name should help.)  Place the appropriate layers within this group.  Do the same for the streams and for the aerial photos.

  4. Editing symbols.  Each layer has a symbol associated with it.  This symbol is used to draw the features from that layer and can be chosen after double-clicking the layer in the Table of Contents.  The blue line used for the Allegheny River banks is too thin.  Thicken it.  Similarly, browse the various choices and choose an appropriate symbol for the State Highway layer.  Discuss whether or not a single symbol for all objects in a layer is a good idea.  

Adding Data

  1. Point Features. The first point features we will add to the system are fire hydrants.  The easiest ways to add point features using data that you collect is by creating a comma-delimited text file containing the data.  In the folder with the rest of the lab, you should find a file named "Campus Hydrants.txt".  Open this file using NotePad.  What are the names of the fields? How many objects do you think are stored in this file (now)?  The file contains headings for the data along with the values for the objects (in this case fire hydrants) that are to be included in the file.  In this case, the locations are given as longitude and latitude.  To add the data file as a layer, choose Add XY Data under the Tools menu in ArcMap.  Browse to, and select this file.  The values for the X and Y fields should fill in, but you will still have an Unknown Coordinate System.  Edit this, and Select the predefined coordinate system: Geographic Coordinate Systems/North America/North America 1983 HARN.prj.  OK everything and wait a moment for ArcMap to load your data.  Change the symbol to the standard fire hydrant symbol [Hint].  How about a thoughtful choice of color, while you’re at it?  Now suppose that you have just learned of another fire hydrant on campus.  This one is named New SBU Hydrant and has coordinates (-78.48460, 42.08032).  Why are the X values all negative in this file?  Using NotePad, add this to the text file and save your changes.  Perform some operation in ArcMap that requires the map to be updated.  Your new fire hydrant should appear (although not instantly; without realizing it, you’re asking ArcMap to perform a lot of complex computations).  Where is the new hydrant?

  2. Point Features, Layer Two.  Now you are to create a new layer for Information Sites on campus.  For now, your layer will have only one point, the kiosk in front of Plassmann.  You are to take the supplied GPS receiver out front and determine the appropriate coordinates for this point.  Can't measure the center of the kiosk exactly?  Here's a hint.  (If the kiosk is problematic, you may use the railing at the top of the steps for the front entrance.)  Then create an appropriate data file and add the data to the map.  Again, choose an appropriate symbol.  What symbol did you choose, and why?

  3. Line Features.  Rather than create a new layer here, we will add a feature to the existing Streams layer. Zoom in on the area where Fourmile Creek enters the Allegheny River.  Explore ArcMap and add two lines to this layer that more closely follow the actual channel of Fourmile Creek.  (There should be one line for each bank.)  Click here if you get stuck.   Open the Attribute Table for Streams and set the ST_NAME and ST_TYPE fields "Fourmile" and "Creek" respectively. (Note that setting attribute data is really an editing operation.  You must be editing the layer or your data will be "read only" and you won't be able to change anything.)  Take a screen snapshot of the display with the edited stream bank clearly visible and copy it into your lab report.  (Include the Table of Contents and other ArcMap elements with this image).

  4. ArcCatalog. Creating a new layer in ArcMap is an easy task, but one that involves non-trivial file manipulation. Thus, ESRI has provided a second program, ArcCatalog, that aids in this task. Read this associated commentary on the role of ArcCatalog.

  5. Area Features.  Add a new Shapefile for "Athletic Fields".  While you are creating the shapefile, add at least 2 data fields to its attribute table.  Choose these fields to reflect the types of information pertinent to athletic fields on campus .  Add as many playing fields to the GIS as you can and fill in the new data fields.  Choose your symbol appropriately.  Save all of your edits.  Take a screen snapshot showing your newly created athletic fields and the associated attribute table, and copy it into your lab report.

To Hand In

You are to create a text document including the answers to the questions/discussion requests posed in this lab.  It should include the attribute table for an athletic field. Please give it the name GIS Lab 2 – your last names.  Your report should include the two required screen snapshots, zoomed appropriately to show your changes and showing all (and only) the layers you modified in the lab.  The write-up should be turned in, along with a cover page.  Email this document to both instructors (dlevine@cs.sbu.edu and georgian@sbu.edu  ).  We often delete spam with little thought, so give your email a clear and meaningful subject line.

Help Policy

       Help Policy in Effect for This Assignment: Group Project With Limited Collaboration

       In particular, you may discuss the assignment and concepts related to the assignment with the following persons, in addition to an instructor in this course: any GIS instructor and any student enrolled in CS 128/ES 228.

       You may use the following materials produced by other students: materials produced by member of your own group.