CS 128/ES 228 - Introduction to Geographic Information Systems

Lab 3b: Coordinate Systems

Goals:

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

  1. Understood how ArcMap determines the map projection of a Data Frame.
  2. Become familiar with some common coordinate systems used in GIS.
  3. Learned how to add data with different coordinate systems to a GIS.

 Fun with coordinate systems:  fire hydrants revisited

  1. Determining the projection of the Data Frame.  Start ArcMap on one of the lab computers and open the supplied data set.  [Note that this is the same data set as for Lab 2.  If you have that one available, you can avoid downloading this one.]   Move the cursor around the map and note the coordinates displayed below the map.  Record the coordinates of the center of the intersection of Rt. 417 and Constitution Avenue.  Without peeking at the Data Frame properties, can you guess what coordinate system it is using to display data?  Which of the coordinate systems you learned about in class do they seem to fit?   Okay – having recorded your guess, get ArcMap to tell you the answer.  What did you find out? 


  2. Investigating a GIS  data set.  The aerial photographs for the campus map you’ve been using in lab were obtained from a GIS web site maintained by the state of New York.  Go to the site and click on “New and Enhanced Digital Orthoimagery…”.  We are using the older NAPP (1994-99) aerial photographs, listed below the newer High Resolution images on the navigation sidebar.  Read through the Data Set Description and record the following:  What was the resolution of the photographs?  What type of film was used?  What coordinate system are they projected in?
                For more details, you will have to consult the Metadata file.  Search the Metadata file for the NAPP photographs, using the Find (on this page) feature available as an Editing option on most web browsers, and determine the following:  What datum and ellipsoid do they use?  What is their original scale?   New York State spans 3 UTM zones.  What was done to get photographs from zones 17, 18, and 19 to match?     


  3. Adding data with a projection different from that of the Data Frame.  Redo last week’s exercise of adding point locations of some of SBU’s fire hydrants to your map, but stop when the Add XY data query box opens.  What Spatial Reference system has ArcMap discovered?  Change it to geographical coordinates and an up-to-date datum.  Use the cursor to display the coordinates of “Yellow Fellow.”  Compare its map location to the coordinates in its Attribute Data Table and comment.  Discuss what you think ArcMap had to do to make the hydrants appear on the Olean quadrangle.

  4. Adding data from a source with an unknown projection.  Go to the Community GIS web page we viewed in the first class.  [Hint]  Open the Town of Allegany GIS and record the locations of the five fire hydrants nearest the intersection of State Highway 417 and Constitution Avenue, including Yellow Fellow.   Create a text file containing the locations, and add to your campus map.  What Spatial Reference system should be used?
                Having trouble finding the new hydrants?  Here’s a hint. What’s wrong, do you think?  (hint).  Have the hydrants now shown up on campus?  Good.  Are they where they belong?  If the match is poor, how might you seek to find and remedy the causes? 
                Once you get the new hydrants in the proper locations, change their symbolization so it contrasts clearly with the hydrants added in step 3, change to layout view, zoom and resize the map appropriately, and print it to file.

  5. What have you learned?  What two errors are commonly made when adding data from a source with an unknown projection?  How are they remedied?

To Hand In

You are to create and email to the instructors a text document including the answers to the questions posed in this lab.  It should have an appropriate cover page.  In addition, you are to print to file and email to the instructors a copy of the map showing all the hydrants you added in the lab.   

 

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.