Elevation.city website provide topographic elevation data for more than 100,000 cities worldwide.
Almost all elevation maps on this site are generated using elevation values from NASA's 90m resolution SRTM data. This information is available for geographic positions from equator up to ±60° latitude (98.8% of cities are in this range). 90m resolution means 3 arc-seconds division.
Above this latitude (closer to poles) GMTED2010 database is used, which is available for the whole planet. This resolution is 7.5 arc-seconds (approx. 225m at equator). Example for this smaller resolution maps: Tromso elevation (Norway)
NASA elevation data is projected to tiles based on openstreetmap data at zoom level 13. Largest cities has another elevation map at zoom level 12, since they are bigger and edges of the city may be out of zoom 13 tile borders. Example: San Francisco elevation (US).
Size of the tile (in kilometers) is available in the elevation map image. On the page it is recalculated into miles too, but base data is in metric systems (meters and kilometers). Imperial units are calculated from metric values. (conversion kilometer to mile and meter to feet)
It is important to understand, that city boundaries are not equal to tile edges. However, there is an elevation data for city from separate database (geonames), statistic about tile elevation (minimal, maximal and average value) is calculated only for that square map, not for the city boundaries.
Dr. Igor Gaspar, webmaster and author of the site.