Attributes in ArcGIS

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

Select by Attributes• SELECT * FROM TableName WHERE:

– “WHERE Clause” or Filters