Field Cleanup

Before you do any modifications tpo a database, you should consult its metadata and insure that you understand what you are doing, so you do not make additional work for yourself. 

Databases may have a number of fields that will not be helpful to you.

  • The area and perimeter fields may or may not be helpful.  ArcGIS sometimes computes them in very unfriendly units.  In this case, they might be in square meters and meters, although km might be more helpful. You can compute these easily at any time, perhaps in more useful units.
  • The next group of fields appear to be filled with 0's, which will not be very useful.  You must insure that what you see in the first group of fields is representative of the entire data set; a Frequency table or list of unique values can confirm your impression.  These are probably left over from database creation or edits, and could have been stripped out before distributon of the database.  These would be very easy to add back in later.
  • The code field is entirely blank.
  • You can delete fields by

 Databases may have fields with excessive length

  • This field has a length that is far too long, and takes up most of the screen.  While you can resize it relatively easily, you might prefer to change it once and not have to worry about it every time you open the database.  You should do this with care, since you cannot add longer text to the field later.
  • To trim the field definitions:

 

Sloppy or Inconsistent Field Entries


This shows the field above, after trimming, and the fields adjacent to it in the database.  These three fields appear to show the same information, in English, a short text code, and in French.  There may also have been coding in Arabic, but that appears to have been trashed before the shapefile was posted on the web.

Note several issues:

  • Some fields have no entries in any of the three fields.  The GIS program will color these all the same, or leave them uncolored, depending on how it was designed to deal with missing attributes.
  • Unit K10 has no text, in either French or English.
  • Unit P2-3 has no coding in French.

The "best" solution here is not clear, and you will have to carefully analyze what the problematic codings should be.

 


Last revision 11/10/2017