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Scenes

A HyperLens® Scene comprises a definition file, a base image, and may include further images or other layers. Within the HyperDAAC scenes are generated automatically as follows:

  1. Each scene is generated in its own directory. The directory name is the scene name; you select it when you generate the scene.
  2. The definition file is named defn.hld. Opening any HyperLens Definition File (.hld) will load the scene it defines.
  3. Data Layers are in HyperLens Image (.hli) format. This is simply raw data (normally compressed), with a header. They are designed to be loaded either locally or over the Internet, and the header is in the familiar RFC822 format used by HTTP, the protocol of the Web.
  4. When you select a layer (from the Layers menu), the software will look for it in the scene's directory. If it is not found, it will be generated: this may take a few seconds (particularly at 1Km resolution). In the case of a layer from the 1Km AVHRR archive, it will be downloaded from the EDC server: this will take several minutes and perhaps hours, depending on your Internet connection and the size of scene extracted.

 

Generating a Scene

[Defining a query area]

The example in this image shows a Query lens defining an area over the Gulf of Mexico and Caribbean at 4Km resolution. Selecting Submit will generate the scene we have defined, and load it into a new HyperLens® window.

You can generate a scene within the HyperDAAC using either the Query or the comp10d lens. If you intend to load AVHRR data layers you should use comp10d; otherwise use Query.

When you open the lens, a small query window will pop up. This defines a scene. As you move the lens, the Line/Sample values will follow it, so when you press Submit the scene extracted is exactly the area selected by the lens. Please select an appropriate resolution for the scene you are extracting: if you select a whole continent at 1Km, the image you generate could be 100Mb per band (100 million pixels), so an 8Km continent or a smaller area at 1Km might be more appropriate.

[Generated Scene with Lenses]

The second image shows a fragment from the scene we just defined. Two lenses are open, with a USGS layer highlighting several classifications uppermost.


 

Deleting a Scene

Since each scene occupies its own directory, you can delete a scene by simply deleting its directory.

See Also