Week 7: Tabular Data Type


Data Types:  Tabular Data

  1. Common types used in GIS
    • xls, xlsx, txt, csv, dbf
    • First 4 types can be viewed in Excel using File>Open
    • To view a dBase file (.dbf), you must open an Excel worksheet and then drag the file from Windows Explorer and drop it into the blank worksheet
  2. Formatting for viewing in ArcMap
    • First row must contain field names
      • Field names must be short (keep them less than 12 characters)
      • Field names must have no spaces
      • Field names must begin with an alpha character (a-z)
      • Field names must only contain alpha-numeric characters (a-z and 0-9) and underscores are OK too
      • Do NOT use strange characters like ~, !, @, #, $, %, ^, &, *, /, and so on
    • Remaining rows must contain the information
      • Each of these rows are called “records”
      • Each record contains the information for one and only one object being mapped (an example might be if we went out and GPS’d all of the light poles on campus; the objects being mapped would be the light poles and they would be represented as points on our map; if there were 400 light poles, we would have 400 records)
      • We call this a 1-to-1 relationship where one and only one record relates to one and only one object on the ground
      • Note: 1-to-many relationships (one record relating to many objects being mapped) are allowed. We will cover this later on.
    • Each column is referred to as a “field”
      • Fields store a common attribute for all records. Some examples
        • total volume of softwood timber: softwoodTotal,
        • total tree height: treeHeight, or
        • the year each stand was established :estabYear
      • Fields are either (these are called data types)
        • short integer: -32,768 to 32,767
        • long integer: -2,147,483,648 to 2,147,483,647
        • float: approximately -3.4E38 to 1.2E38 (big decimal number)
        • double: approximately -2.2E308 to 1.8E308 (larger than float)
        • text
        • Date: mm/dd/yyy hh:mm:ss
      • All values in a field must be of the same type

L2_arcgis-data-types.pdf:  ftp://ftp-fc.sc.egov.usda.gov/GIS/training/arcgis/tips-tricks/arcgis-data-types.pdf

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