Difference between revisions of "Creating KML Files"
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If you choose a '''Path''' or '''Polygon''' you will click multiple times along the geometry you wish to add. Polygons are closed by default, while paths are open. With the path or polygon tools you can either | If you choose a '''Path''' or '''Polygon''' you will click multiple times along the geometry you wish to add. Polygons are closed by default, while paths are open. With the path or polygon tools you can either | ||
| − | * click multiple times to define | + | * click multiple times to define ''regular'' geometry, or |
| − | * click and drag to | + | * click and drag to define ''free-form'' geometry. |
===Example Usage=== | ===Example Usage=== | ||
Revision as of 21:34, 13 January 2013
Introduction
This tutorial covers the basics of creating KML files. We will be using Google Earth to create KML files containing points, lines, and polygons, the three basic geometries involved in vector-based GIS.
Geometry types
A quick description of the basic geometry of GIS will be helpful.
There are three primary geometric types in most GIS applications.
Point
A point is a single 'spot' in space. It has no dimension, i.e. no length, width, or height. Points are typically defined by a set of coordinates, also known as a coordinate tuple. Two examples of coordinate sets include:
- (X, Y)
- (X, Y, Z)
Further reading: Wikipedia: Point
Line
A line is built of points. A sequence of points will form a line. For example:
- ((X, Y), (X, Y), (X, Y))
Further reading: Wikipedia: Line
Polygon
A polygon is similar to a line, except that its start and end points are the same. In effect, polygons are closed loops. Polygons form an area, and can have loops cut out of them.
Further reading: Wikipedia: Polygon
Install Google Earth
Skip this step if you already have Google Earth installed.
- Visit the Google Earth website to download the installer.
- Follow the install instructions particular to your Operating System.
- Launch Google Earth and proceed to the next section.
Zoom to an Area
Use the Navigation Controls or your mouse to zoom in to a location. If you are unfamiliar with navigation in Google Earth, take a moment to go through the Navigation in Google Earth tutorial.
Create map geometry
A placemark is a point, line, or polygon that is used to indicate a specific, or general, location. We will look at the general procedure to create any type of placemark (point, line, or polygon).
Type
First, choose the type of placemark you would like to add.
-
Placemark (Point) -
Path (Line) -
Polygon
If you choose a Placemark (Point), you simply click once on the map to add your mark.
If you choose a Path or Polygon you will click multiple times along the geometry you wish to add. Polygons are closed by default, while paths are open. With the path or polygon tools you can either
- click multiple times to define regular geometry, or
- click and drag to define free-form geometry.
Example Usage
- Points are good to indicate singular locations such as an address point, fire hydrant, or other small feature.
- Lines are useful to indicate roads, rivers, trails, etc..
- Polygons can be used for features such as building footprints, wildlife areas, bodies of water, etc..
Geometry attributes
Once you begin adding geometry (a point, or points in a line or polygon), a dialogue box will appear. This dialogue box has several sections, depending on the geometry type you are creating.
Description
The description tab contains a large text area where you add notes about the geometry.
Style
Altitude
Measurements
Line
- Distance
Polygon
- Perimeter
- Area
