GIS Brownbag Series Attributes

In the beginning… Earliest GIS systems did not have attributes Needed separate layers for labels (e.g. names) CAD software still maintains different separate layers

Amelia Earhart

Shapefile showing Amelia’s last flight Right-click on the name of the shapefile for the flight path to open attribute table

LENGTHFROM_CITYTO_CITY OaklandTucson TucsonNew Orleans New OrleansMiami MiamiSan Juan San JuanCaripito CaripitoParamaribo Attributes: Length FROM_CITY TO_CITY

Feeding sites of a chimp called “Fifi” Aerial photograph of Gombe National Park. Feeding sites stored in a shapefile or personal geodatabase Aerial photograph stored as a raster

Raster attributes Number of attributes attached to rasters is limited

Shapefile or Personal Geodatabase Attributes Many attributes can be attached to each feature OBJECTID and Shape attributes are automatically generated by ArcGIS

Attributes can be: Numbers (whole or with decimal places) Names or text Dates Hyperlinks

Depending on type of attribute different maps can be created This map was created based on text attribute Numbers allow to display population size

Depending on type of attribute different analysis can be done What if you want to show the area for each County?

Adding fields to an attribute table Step 1: Create a new attribute that will hold the area B. Click “Options” button. Then select “Add Field” A. Open attribute table If “Add Field..” is “greyed-out” stop edit session and try again

Pick any name you like. Must be < 11 characters Other choices: Text, Date, Short or Long Integer Number of spaces to store a number Number of decimals. E.g

The new attribute “Area” has been added! Right-click on “AREA” and select Calculate Geometry Notice how all the area’s are set to “0” Step 2: Calculate the area

Joining other data to attribute tables Table with population size for each County Goal: show those numbers on a map Solution: join this data to the shapefile from previous slide Step 1: Save your data in Excel as a DBF4 file

Add your.dbf file to ArcMap

Determine how you are going to join your data Join “population” table to shapefile Look for a primary key: an attribute that both tables have in common and that can be used for the join. Here: both tables have County names

Joining tables Right-click on the shapefile

Choose “No” Make sure that primary key is the same data type in both tables: E.g. you can not join numbers to text.

Data from shapefile Data from “population” table we joined to the shapefile

Tip: export joined table to new shapefile

Map showing population size for each County Maybe population density would be a more informative map..

Density is “POPULATION” / “AREA”

Add a new field to store density attribute

Right-click on DENSITY

Types of Relationships This is a one-to-one relationship One record in the shapefile matches one record in the population table

FIDName 0Joe 1Kelly 2Dan 3George 4Spencer 5Mike NamePet JoeCat JoeDog KellyCat DanDog MikeSnake MikeCat MikeHamster Is this a one-to-one relationship? ? Types of Relationships Can we join this data? NO! Instead of “join”, use a “relate” NO! It is a one-to-many

Relates: Example DBF table with information about a few different laterals Goal: we want to look at those laterals on a map

This is the NHD: it has the geometry Relate NHD to the laterals table This is a one-to-many relationship

H Canal is selected

Use “info” tool on this line segment Attributes for that line segment By clicking the + you see related tables

Tables that NHDFlowline layer is related to By relating tables the user has much more information at “his/her fingertips”

Upcoming Brownbag Lectures May 20: Model Builder June 17: How to make maps that communicate Check out previous Brownbag Presentations on WEnet