Feature Types:
There are three types of Feature which can be mapped:
- Points, Lines and Areas.
- Point: A Point Feature is a single GPS coordinate position which is identified with a specific Object.
- Line: A Line Feature is a collection of GPS positions which are identified with the same Object and linked together to form a line.
- Polygon: An Area Feature is very similar to a Line Feature, except that the ends of the line are tied to each other to form a closed area.
Describing Features-attributes:
- Categories of descriptions for a Feature are known as Attributes of that feature.
- Attributes can be thought of as questions which are asked about the Feature. For example the Attributes of the Feature "house" would be "color", "size", "cost" and "occupants".
- A Feature is the object which will be mapped by the GPS system. The ability to describe a Feature in terms of a multi-layered database is essential for successful integration with any GIS system.
- For example, it is possible to map the location of each house on a city block and simply label each coordinate position as a house. But the additional information such as color, size, cost, occupants, etc. will provide the ability to sort and classify the houses by these categories.
Describing Attributes-Values
- Logically, each question asked by the Attributes must have an answer.
- The answers to the questions posed by the Attributes are called Values. In the example above, an appropriate Value (answer) for the Attribute (question) "color" may be "blue".
- The following table illustrates the relationship between Features, Attributes and Values:
By collecting the same type of data for each house which is mapped, a database is created.
Feature List:
- The Feature List is a database which contains a listing of the Features which will be mapped, as well as the associated Attributes for each Feature.
- Feature List also contains a selection of appropriate Values for each Attribute.
- When a Feature List is used in the field, the first step is to select the Feature to be mapped. Once a Feature is selected, the Attributes for that Feature are automatically listed. A Value for each Attribute can then be selected from the displayed list of predetermined Values.
- Objective of making a feature list: To simplify the data entry process.
Exporting to a GIS System:
- The final step in integrating GPS data with a GIS system is to export the GPS and Feature data into the GIS system. During this process, a GIS "layer" is created for each Feature in the GPS job. For example, the process of exporting a GPS job which contains data for House, Road and Lot Features would create a House layer, a Road layer and a Lot layer in the GIS system. These layers can then be integrated with existing GIS data.
- Once the GPS job has been exported, the full power of the GIS system can be used to classify and evaluate the data.
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