Tuesday 28 August 2012
Attribute Data
I’ve been looking into one of my favorite topics, Geodatabase design and implementation recently and I’m having a lot of fun with it.I will actually be going into the subject very soon. An associated concept is attribute data and a good understanding of it will help you actually grasp the concept. I therefore urge you to read this post carefully.
Features are things you can actually see on a landscape such as roads, buildings etc. Features have geometry (point, polyline or polygon) and attributes which describes the feature. For example in the table below,
| Dataset Entity | Spatial Data | Attribute (Tabular)Table |
| Soil Class | Polygon | Surface Rockiness, |
an entity such as a soil class with a spatial data type of a polygon can have attributes shown in the attribute(tabular) column.
Attributes for a vector feature are stored in tables.Tables are composed of columns and rows. A column represents a list of the types of items that each table will store and commonly referred to as a field.Each field in the attribute table contains contains a specific data type i.e text,numeric or date. A row, a record or tuple on the other hand refers to a line of data within a table.The records in the attribute table in a GIS each correspond to one feature.The GIS application links the attribute records with the feature geometry so that you can find records in the table by selecting features on the map, and find features on the map by selecting features in the table. A typical example of an attribute table layout is shown below.
| Attribute Table | Field 1 | Field 2 | Field 3 |
| Record 1 | |||
| Record 2 |
Importance of attribute Data
- Setting feature symbology
- Attribute data can also be useful when creating map labels.
- useful in carrying out spatial analysis.
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