My Google Map Blog

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This is at the Sambadrome Marquês de Sapucaí where the Rio Carnival take place in Rio de Janeiro, Brazil. Larger

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We mentioned in our post on simulating lakes that Google Earth’s elevation data is often very inaccurate in mountainous areas. When looking around the 3D imagery of Rio de Janeiro, where the Olympics are currently taking place, we realised it would be an ideal place to actually check how inaccurate Google Earth’s elevation data can be.

We will start with Sugarloaf Mountain. Drag the slider on the image below to compare Sugarloaf Mountain as seen with the 3D buildings layer turned on or off.

Left: With 3D buildings turned on. Right: with 3D buildings turned off

Google Earth actually shows the peak of Sugarloaf Mountain to be at sea level, with an elevation of 0 m. The hill to the right of it fares better with a maximum elevation shown as 33 m. Interestingly, we discovered that when you turn on the 3D buildings layer, Google Earth does actually show elevations from the 3D imagery in the status bar and reports 406 m for the very top of the cable-car building on the top of Sugarloaf Mountain, and 235 m for the top of the tallest tree on the neighbouring hill. So, even assuming Google Earth should show ground level altitudes when the 3D buildings layer is turned off, it is still out by over 400 m for Sugarloaf Mountain.

For the famous statue, “Christ the Redeemer”, the peak is shown at about 500 m with the 3D buildings layer turned off, and about 700 m with it turned on, a difference of over 200 m.

Left: With 3D buildings turned on. Right: with 3D buildings turned off

If we do an elevation profile of the route to the summit at the statue of “Christ the Redeemer”, even with the 3D buildings layer turned on, the elevation data used is the inaccurate data as shown when the 3D buildings layer is off.

The elevation profile shows a dip of over 100 m at the end when it should instead have climbed to an altitude of 700 m.

The above locations are extremes and most other peaks around Rio have smaller discrepancies, but where the terrain is particularly steep the discrepancies can still be significant.

The post Rio 3D imagery and Google Earth’s elevation data appeared first on Google Earth Blog.