attributes in arcgis. arcgis attributes fid – esri’s internal identifier shape – actual...
Post on 13-Jan-2016
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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”
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
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
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
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 * FROM TableName WHERE:– “WHERE Clause” or Filters
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