Online Mapping - KML and Google Earth Flashcards
What does KML stand for?
- Keyhole Markup Language
What is the definition of KML?
- XML based format
- Stores and models geospatial data
- Can store descriptors like text, polygons, points, lines, images and 3D models
What is XML?
- Flexible way to story data
- Data is categorized by user defined tags
- Data can be organized to custom specification and yet remain machine-readable
How does google describe KML?
- Tag-based file format used to display geographic data in an Earth Browser
What act as browsers for KML files? Why is the browsing function important?
- Google Earth and Maps
- Browsing function enables sharing of data and maps freely
What is a Tag?
- Simply and intuitive code that tells the software what to do
- Describes the manner in which certain features and text are displayed
What can we do with KML?
- Take locations and specify the manner in which the labels display
- Ground and image overlays with georeferenced data
- Screen overlays (click and drag image to fit
- Change/apply styles
- Use HTML to define the way text looks, embed pictures and/or videos
- Paths, points, polygons
- Incorporate time tags and animate
What is the breakdown of a basic Placemark script?
Placemark name /name Description /description Point Coordinates /Coordinates /Point /Placemark
What is necessary to open and close a KML script?
The opening and closing tags
What differentiates a KML script from a text file?
- The opening xml and mL tags
What is the purpose of indentations in a script?
- To help organize a script, but are not necessary
- To keep track of what is happening in a script
What does decimal degrees for the west require, especially in a script?
A - in front of the West coordinate
Which comes first for a coordinate in a script, latitude or longitude?
- Longitude, followed by Latitude
What must a KML script end with?
/kml
What is the purpose of the 3rd number in a coordinate string?
- The 3rd number is the elevation of the point
0 sits on the ground
> 0 floats above
What does a CDATA! tag do? Why is this useful in KML?
- The KML treats the text as characters
- Useful because simpler HTML text can be used inside the CDATA!
- Can change text, add website links, videos, photos etc.
What is one of the biggest advantages of using a CDATA! tag?
- Anything that can be defined in HTML can be added to the map
- Ability to write a web address simply as it is without an a href=”www….”
- Web links are far more complicated to use in KML without CDATA!
Why should a script be written in a text editor like Notepad ++ or Text Wrangler and not word?
- Word can have hidden code that will affect a script
What are some common HTML elements?
- <h1> h1 makes a heading sized font</h1>
- <p> p is a paragraph break</p>
- <i> i is italics</i>
- <b> b is bold</b>
- change font colour, use hexadecimal
What format should colors be referenced in?
Hexadecimal
How can videos be embedded in KML?
- Youtube videos come with an embed code that allows a video to be played directly in the mapping application without having to leave it
- Place rich web content directly into the description balloon with CDATA!
What does a Ground Overlay do?
- Drapes a georeferenced image onto Google Earth
- Can add transparency too
What coordinate system does a Ground Overlay system need to be in?
- Geographic Coordinate System of Lat/Long
- 8-bit
- Need full extent of image
What is a Screen Overlay?
- Manually stretch an image over a location in Google Earth
- Can distort an image easily when stretching
How can the extent of a georeferenced image to be used in ground overlay be found? What is an issue with the extents usually?
- Right click and check properties in ArcGIS
- Metadata, especially from Gov’t sources (Topographic maps)
- Issue: Extents not very precise (1 or 2 decimal points)
What image format should be used for overlays?
- Tiff
Why is a Ground Overlay Useful?
- Good visualization tool
- See change over time by stacking layers (change analysis)
What is good about using Toporama’s for Overlays?
- Purely geography
- Excess titles, legend, etc. have been removed
What does the Icon tag do in a Ground Overlay?
- Tells the code exactly where to find the file to use
- Can be located anywhere on a hard rive (local location) or web server (Cloud)
What does LatLonBox do in a Ground Overlay?
Defines the corners for the bounding box (extents)
- Where image is located on the ground
- can use a if needed
What image formats are supported by Google?
- Usually jpg is used
- Can also support bmp, gif, tiff, tga, png
What is a Path?
- Similar to line feature in ArcGIS
- Highly customizable
What is the KML tag for a Path? What other elements (tags) are associated with it?
- All contained within a
What does Extrusion do in a path?
- Extrudes the path above the ground by an elevation in meters
- Elevation set as 3rd value in coordinates
What does the Tesselate tag do in a LineString?
- Enables path to follow the terrain
- Set as a boolean value (0 or 1)
- Need to set altitude element as well in order for tesselate to work
- Best for Global scale, not local
What are the settings that can be used in altitudeMode?
- clampToGround
- relativeToGround
- absolute
What is the default altitudeMode?
clampToGround
- Path or point will be on the ground
- Ignores the 3rd value in the setting
What is the altitudeMode relativeToGround?
- A set elevation above ground height
- Each coordinate will be a certain specified value above the ground
- Example: Powerlines or street lamps that would all be the same height above the ground
What is the altitudeMode absolute?
- Set relative to sea-level
- If elevation is set to 7m above sea-level and terrain is 5m, point will be drawn at 2m above terrain
What are the requirements when creating a polygon?
- Placemark
- Polygon
- outerBoundaryIs
- LinearRing
- Coordinates
- must be set in counterclockwise manner and 1st and last must be identical (or somewhere side-by-side in the coordinate list)
What are other options for polygon styles?
- Extrusion
- Custom colours and shades
- Transparency
What is a Style in KML?
- Defines the look (colour etc.) of features once
- Called later in the script to use without having to define with each use
- Very customizable
What is a shared style in KML?
- A Style that is called more than once
What can types of features can Styles be used for?
- Geometry
- Placemarks
- Overlays
How can Styles be defined?
- Internally in the script and reference them later
- Externally on website or another mL that only stores styles
How are Styles called in a script?
- Internally with #uniqueID (identifying Style id defined with the Style tag earlier)
- Externally with an to a web server or link to a style
How are colors defined in KML?
- Hexadecimal
- Range is 0-255 (00 to ff)
- aabbggrr
- aa=alpha (00-ff)
- bb=blue (00-ff)
- gg=green (00-ff)
- rr=red (00-ff)
- Can also use common color names that Google recognizes
How does 00 to ff define colors?
- ff is fully transparent
- 00 is fully opaque
ex. 00 is fully blue, ff is no blue
What color is ff000000?
Black
What color is ffffffff?
White
What is a Balloon?
- A pop-up box containing info for a feature in KML
- Contains descriptions, rich text, videos, photos, etc.
- Can change look with Styles (colors, templates, etc.)
What are 2 tags that can be used to define a BalloonStyle?
- bgColor for background color
- textColor for font color
What does the LookAt tag do?
- Defines how a placemark will be viewed from a distance
- Within the Placemark tag
What tags are used in a LookAt?
- Longitude
- Latitude
- Altitude (above ground)
- Heading (azimuth relative to N, 0 to 180, or 0 to -180)
- Tilt, angle (0 for birds eye, 90 for ground level)
- Range, how far away from the long/lat
