SRTM Forum
Welcome to the SRTM Forum.  This is a discussion forum for users of data from the Shuttle Radar Topography Mission.
 


Return to Website

  Reply
  Home

Subject:   Re: Spatial resolution depending on latitude
Name:   Tom Farr
Date Posted:   Aug 23, 07 - 8:35 AM
Email:   tom.farr@jpl.nasa.gov
Message:   Eric,
Each pixel of the SRTM data represents either 1x1 arc-sec of lat x lon or 3x3 arc-sec. Thus they're about 30 m or 90 m at the equator and decrease by the cosine of the latitude as you go to higher latitudes. That's why you get the same number of pixels/degree no matter what latitude. This representation is sometimes called geographic projection, or 'no' projection. When you project the data (say to a Mercator projection), you convert the arc-sec representation to m.

As a side issue, sometimes people confuse the pixel spacing with the resolution. SRTM's resolution was about 40-60 m depending on the terrain (we used an adaptive filter). We chose to make the pixel spacing, or postings, 1 arc-sec to make sure we captured all the spatial resolution there was. The DoD made us average the 1 arc-sec to 3 arc-sec for non-US areas.

Hope that helps,
Tom Farr
Replies:    
Spatial resolution depending on latitude by Jamie Halperin · Jan 6, 08 - 6:47 PM


  Reply
  Home


powered by Powered by Bravenet bravenet.com