Wednesday, March 25, 2009

Earth from Space

Checking out the Earth from Space is somewhat akin to falling into a black hole - it sucks you in and you can't get out. This is a great collection of images of planet Earth taken by astronauts during space flights or time spent at the International Space Station. Created for the purpose of publically showcasing NASA's extensive collection of Earth imagery, the Earth from Space collection provides a "best of" look at images that highlight distinctive Earth features and processes such as hurricanes, volcanoes, cities, water habitats, and more. Each image, available in three resolutions for viewing as well as larger sizes for download, is accompanied by detailed cataloging metadata and a caption that includes interesting and relevant information and provides context for the image. Some images also include annotations that help provide further clarity. Unfortunately, most of links on the Earth from Space homepage have not been updated so FAQ and other types of information are neither timely nor completely accurate. This can be problematic if a user discovers the Earth from Space site prior to discovering or exploring the Gateway to Astronaut Photography of Earth which is where the current information about NASA's complete Earth imagery database and the special collections like the Earth from Space collection can be found.

The complete database contains 798,810 images as of March 1, 2009. The Earth from Space collection is a small subset of those images - 2,613 images - with the most recent image, Mawson Peak, Heard Island, dated February 28, 2009. The Gateway portal links to the outdated Earth from Space collection homepage, but that is most likely for navigational purposes. It is much easier to discover resources within the collection from the collection homepage than it is utilizing the search feature for the complete database. The collection can be searched using the search pages or a clickable map.

Selection Decisions/Collection Principles
  • No information available about collection development policy other than the statement that the pictures selected are deemed 'best of'
  • The collection's FAQ page does not provide current or completely accurate information about collection characteristics, but current information is available from various links on the Gateway homepage
  • New images are being added to the collection, but that is only discoverable by experimentally searching by dates from the collection's Technical Search page or by refining a search of the database from Gateway Technical search page
  • Server statistics that record the number of downloads from the database as a whole are available, but not from the collection's homepage
  • Images in the collection are publically and freely available, even to those with low-bandwidth connections and tips for viewing, printing, saving, and transforming the images are available from a link on the search results page
  • Sustainability over time and interoperability have been considered as noted on the Database Content page

Object Characteristics

  • Objects available on the Web exist in JPG formats of varying sizes and can be viewed or downloaded
  • Most images acquired with digital cameras are transmitted from the shuttle or the space station via a ku-band communication system and archived in a proprietary Kodak format (KDK); however, if the ku-band was unavailable images were downlinked in JPG or TIF format
  • Images originally captured on film have been digitized using various methods including the use of video technology, scanning by hand, or scanning in batch mode (no particular details available)
  • Images in the Earth to Space collecton have been color corrected by hand, but that is not typical for most images in the complete database
  • Object names are the same as the file name but those names conform to the following naming scheme: mission-roll-frame_version.type where _version only exists if the version is not NULL
  • Metadata specific to the digital image includes file name, file size in bytes, height and width in ppi, image editing (e.g. cropping or annotation), image availability (i.e. web-viewing or special request), purpose, and comments
  • Camera information is available via a pop-up screen
  • 25 other fields of metadata are also available - see the Database Fields page


  • As noted, in the Object Characteristics, extensive metadata is available for each object
  • Metadata about the collection itself is limited (see Collection Principle section)
  • The Database Content page notes that metadata conforms to community standards and is created with current and future users and interoperability in mind
  • Object metadata exists as unique records within the database
  • The conditions and terms of use available as a link from the collection's FAQ is not as current as the statement available from Gateway page

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