The data were then resampled to a Mercator projection with approximately square pixels (about one kilometer, or 0.6 miles, on each side). For this broad view the resolution of the data was first reduced to 30 arcseconds (about 928 meters north-south but variable east-west), matching the best previously existing global digital topographic data set called GTOPO30. This image of South America was generated with data from the Shuttle Radar Topography Mission (SRTM).
