3. Attribute Data (Part 1)

Duration: 4 minutes and 58 seconds

Country: South Africa

Language: English

License: CC - Attribution Non-commercial No Derivatives

Genre: Instructional

Producer: Chief Directorate: Spatial Planning & Information, Department of Land Affairs, Eastern Cape, South Africa

Views: 165 (20 embedded)

Posted by: giacomo on Mar 30, 2010

Understanding the role of attribute data in a GIS. Attribute data describe features. Attribute data can help us to make interesting and informative maps, and perform spatial analysis in a GIS application. In this topic we describe how attribute data are associated with vector features and can be used to symbolise data.

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Hi, my name is Lerato.
Welcome to the next topic in our Gentle introduction to GIS series.
In this topic we will look at attribute data.
In our last topic we looked at vector data and discovered that vector features have a geometry and attributes.
While the geometry of a feature defines its shape and position, ...
... the purpose of attribute data is to describe features.
Imagine if every line on a map was drawn with the same colour.
It would be very hard to see what is going on.
We can colour maps because we know things about the different features they represent.
For example we know this road is a secondary road ...
... and that this one is a track.
Drawing them in different colours helps us to make sense of the map.
It is the attribute data that provides the information we need, to obtain the meaning from maps.
Every feature has characteristics we can describe.
For example, this house has properties such as: ...
... roof colour and a balcony which helps us to describe it.
Attributes can also be things we know about the house but can't necessarily see.
For example, we may know the year in which it was built.
The attribute may also be the absence of a property such as: ...
... this house which has no balcony.
While we look at the geometry of features in the map view, ...
... we look at their attributes in a table view.
Each different attribute is shown in the table view as a column, or field.
Each row in the table view represents one feature. Table rows are also known as records.
Clicking on a row in the table view will highlight that feature on the map.
The fact that the GIS Application knows what attributes each feature has opens up many possibilities.
Using the attribute data we can tell the GIS Application to draw our features based on their attributes.
For example, we can colour code these house polygons based on the colour of their roofs ...
... or based on whether they have a balcony or not.
We can also use the attribute data to create labels for features based on a property.
The attributes are also useful because they enable us to search for features.
If you ever spent hours looking for something on a paper map ...
... you will realise how useful this capability is!
In our next screencast, we will continue the topic of attribute data, ...
... by looking at symbology that can be defined, based on attributes.
Thank you, see you next time.