Skip all navigation and jump to content Jump to site navigation Jump to section navigation.
NASA Logo - Goddard Space Flight Center + Visit

+ Advanced Search
SVS Searches.  The following buttons are searches through SVS images.
View Most Recently Released Imagery
View Gallery of Imagery: A topical collection of SVS Imagery
Search Imagery by the keywords assigned to it
Search Imagery by the instruments that supplied data for a visualization product
Search Imagery by the series of visualizations that have been produced
Search Imagery by the scientist providing the data used in a visualization product
Search Imagery by the animator that created the product
Search Imagery by the identification number assigned to the visualization product
See other search options
Learn about the SVS Image Server
  + About the Server
  + Animation List
  + How to Use the Server

  + RSS Feeds
blank image

SVS Image Server

Design Considerations - Projections

In computer graphics terminology, a "texture map" is an image that is displayed on a 3D object in order to simulate the surface appearance or texture of the object. The most common method to create a 3D model of the Earth is to "wrap" a 2D image or map of the entire Earth around a sphere.

In order to use an image as a texture map, the exact correspondence between pixels in the image and points on the sphere must be known. If the image of the Earth is an Equirectangular map (also known as Platte-Carree or Equidistant Cylindrical), then the pixels of the image are laid out in a regular longitude-latitude grid and mapping the image to a sphere is easy.

In order to facilitate both the use of our images as texture maps and overlaying multiple images, all images served by the SVS Image Server use the same projection, an Equirectangular projection based on the WGS84 datum. In WMS 1.3.0, this is indicated by the line

<BoundingBox CRS="CRS:84" minx=minLongitude miny=minLatitude
   maxx=maxLongitude maxy=maxLatitude/>

within a Layer definition in the Capabilities XML, which becomes


in the GetMap query to the server. In WMS 1.1.1, the syntax is somewhat different, becoming

<BoundingBox SRS="EPSG:4326" minx=minLongitude miny=minLatitude
   maxx=maxLongitude maxy=maxLatitude/>



The SVS Image Server supports both WMS version 1.1.1 and WMS version 1.3.0. When requesting an image with a GetMap request, one of these two versions must be given (with VERSION=). When requesting an image with WMS 1.1.1, the parameter SRS=EPSG:4326 is required, while CRS=CRS:84 is required when using WMS 1.3.0.

Go backward to "Design Considerations - Fixed Size Images"

Go forward to "Styles and Legends"

Table of Contents

     SVS Image Server Home Page

     Tutorial Introduction
     Accessing the Table of Contents
     Asking for an Image
     Asking for an Animation
     Asking for an Image Sequence
     Design Considerations - Fixed Size Images
     Design Considerations - Projections
     Styles and Legends
     Metadata - Abstracts and Keywords
     Metadata - Attributions and FGDC Metadata


     Available Animations List logo - the U.S. Government's official Web portal. + Privacy Policy and Important Notices
+ Reproduction Guidelines
NASA NASA Official:
SVS Contact: