Saturday, April 3, 2010

64 Acres of iPads

Imagine 64 acres iPads sitting edge to edge. That is how many you would need to display the entire Scenic Map Central USA at the maximum resolution.

If you zoom all the way in to show the maximum detail in Scenic Map, how many pixels would be needed to display the entire map? Let's take Scenic Map Central USA as an example. It's data runs from 28 to 48 North Latitude and 94 to 114 West Longitude. That is a square of 25 degrees on each side. Each degree at the highest resolution produces a square image of 97200 pixels on each side. The entire image with all the degrees would be a square 2.43 million pixels on each side. The total number of pixels in the entire map is 5,904,900,000,000 or 5.9 trillion. Each pixel contains RGB components and if they were stored as raw bytes, the disk space required would be about 16.1TB. This is why storing pre-rendered images requires a Google sized server farm. It also is why map apps that store their offline data as images require so much storage space or have a very limited coverage area.

An iPad's screen resolution is 1024x768. Adjusting for the squeeze caused by the map's projection, you would need about 5.6 million iPads placed next to each other to display the Scenic Map Central USA at the maximum resolution. They would cover 64 acres. You should multiply these numbers by three if you want to consider the entire USA.


  1. How large would the map of iPads be laid out side by side to show high resolution? For example, 300 feet by 600 feet?

  2. Let's say an iPad in portrait modes displays 1024x1024 map pixels taking into account the squeeze caused by the map's projection. An iPad is 9.56 inches high and 7.47 inches wide. Scenic Map Central USA would require 2373x2373 iPads and cover an area of 1890.5 feet high and 1477.2 feet wide. This is exactly 1/10th of a square mile or 64 acres.