Attributes in ArcGIS

ArcGIS Attributes

• FID – ESRI’s internal identifier• Shape – Actual spatial data

Adding Fields

• Make sure the Shapefile is not marked as Read-Only

• Make sure you’re not in an edit session• Select “Add Field” from the Options

menu• Name the field• Select the type of data• Careful with “Precision”

Checking the Shapefile

• Use the “File Explorer” or “My Computer”• Select all the files for the Shapefile by:

– Shift-clicking each file– Drag the cursor over all of them

• Right click on one of the selected files• If “Read-only” is checked:

– Uncheck it– Click “OK”

Checking the edit session

• Right click on the menu bar• Select “Editor”• If “Start Editing” is grayed out:

– Select “Stop Editing”

Adding Fields

Naming Fields

• Arc only allows 10 characters• Remember you’ll be using the Name in

calculations and queries!

Select the Field Properties

• If you change the precision or scale:– Arc map may change the type for you!

• Types:– Short Integer: 16-bit integer (5 digits)– Long Integer: 32-bit integer (9 digits)– Float: 32-bit floating point – Double: 64-bit floating point – Text: up to 254 characters– Date: MM/DD/YYYY format

Precision can change “Type”

• ArcGIS will change the “Type” if you put in a precision that is beyond the specified type

Delete a Field

• Must be outside an edit session

Editing Attribute Values

• The attribute “table” contains rows and columns similar to a spreadsheet

• However, it’s history and future are based on databases:– Columns=Fields– Rows=Records

• We can add and delete columns (fields)• Adding and deleting features adds and

deletes rows

Calculate Geometry

Editing Attribute Values

• If attributes won’t change:– Make sure you’re in an edit session

• Double click on the cell to type in a new value

• Use the “Field Calculator” to change entire columns

Start Editing

Starting an Edit Session

• Without an Edit Session – ArcGIS will not track your changes so “Undo” will not work!

Making Changes

• Click (or double-click) in the cell• Type changes – easy!

– Dates are in MM/DD/YYYY format

Stop Editing!

• If you don’t select “Stop Editing”, your changes will not be saved

Coordinate Attributes

• It is common to see Lat/Lon or Easting/Northing in attribute tables for point layers

• These are not the values used to render the spatial data!

• These values are not updated when you project, edit, or transform the spatial data!

• To update these columns…

Selection

• Selection tab on TOC• Manual Selection

– Click to select– Shift-click to add/remove from selection

• Select by Attributes• Select by Location• Right click on layer -> Selection ->

Create Layer From Selected Features– Then, “Export” the data to a new file

Select by Attributes

http://jan.ucc.nau.edu/~rcb7/namNm15.jpg

http://jan.ucc.nau.edu/~rcb7/namNm15.jpg

Select by Attributes

• SELECT * FROM TableName WHERE:– “WHERE Clause” or Filters