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Wednesday, January 12, 2011

Q & A: It's All Relative!

Question:
Can I have my students create projects so that everything is "relative"?

Answer:
You can have relativity in a GIS project. You just need to plan ahead.  It's harder to get relativity after you've already created the project.  ArcMap does relativity well when we tell it at the beginning of the project.
Without getting into too many hairy details, here's the simplified, general process:
  1. Plan your folder architecture before you start creating your GIS project.
  2. For example, a good ol' standard is to have a general folder, a MASTER FOLDER if you will, for the whole thing that contains the *.mxd, a folder for images, a folder for links, a folder for metadata and a folder for geodatabases.  Each of those folders contains the individual files(i.e. images has all the *.tiffs and *.jpgs, etc). See attached picture. For educational environments, I add a folder for documents (lesson plans, student handouts, etc.)
  3. Collect and move files into the folders BEFORE you add them to your map document in ArcMap.  You may have a working area that different that your master folder and master map document.  I do this often when I'm still trying to figure out exactly what the final product will become.
  4. Start an empty map document in ArcGIS/ArcMap.  Set all your environmental things (home directory, default geodatabase, document properties, etc).  
  5. Set the "relative" characteristic for your map document. (File, Document Properties, Data Source Options, Store relative path names, Make this the default for new map documents, OK, OK)
  6. Save your *.mxd in it's permanent home folder, the MASTER FOLDER. You're telling ArcMap that all files will "relate" to this location.  It won't care if it's on a hard drive, CD or flash drive.  It just knows to look in it's own backyard.
  7. Now, as you begin to build your map document and do analysis, everything you do goes into this one area (MASTER FOLDER) for the project.  
This process is helpful for your students.  They need good data management skills as they learn how to do GIS. It saves many conversations like "where is the original data?" and "didn't you write anything down?"  We laugh because we've all been there!  In education, transportability (relativity) is important since we may not always be sitting at the same computer.

1 comment:

Senthil Thyagarajan said...

relativity can be used when you are having your data on network drive and you would like to use UNC paths. Helpful when you are working on ArcGIS Server.