Resolution and Accuracy in Google Earth
Most land areas in Google Earth are covered in high quality satellite imagery that has a resolution of 15 m per pixel. You will find that some population centers are covered using ortho photography (aircraft imagery) with many pixels per meter. Oceans (water bodies) and islands are covered at a lower resolution. Islands off southwest England are covered at a resolution of 500 meters or less.
Google has resolved inaccuracies in vector mapping service since the release of this software. An example of inaccuracy was the absence of Nunavut territory of Canada. The territory was created in April 1, 1999. These mistakes were rectified by data updates in 2006. Recent updates have increased coverage of detailed photography, especially in areas of eastern and Western Europe, however not including Ireland, as imagery here, remains extremely limited.
Not all images are taken at the same time. They are current to within 2 to 3 years. Sometimes the images are incorrectly stitched together. You will notice updates to photographic database only when there are drastic changes in the appearance of landscape. Place names and road details vary from one place to another. They are very accurate in Europe and North America but good news is that regular mapping updates are now improving coverage elsewhere.
Sometimes errors occur because of the technology that is used for measuring the height of the terrain. For instance, tall buildings cause one part of a place to be rendered as small mountains, when in fact it is small. Height of Eiffel tower creates a very similar effect in rendering of Paris.
Elevations that are below sea level are sometimes listed as sea level. For instance, California, Death Valley, and Dead Sea are all presented as 0 m, however salton city is about 38 m below sea level, dead valley is approximately, -86 m and Dead Sea is -421 m. However, the Google Earth team has now rectified these mistakes. In addition, when Google Earth was launched, some steep mountain ridges were appearing in an incorrect manner as their shadows were extending south facing sides. However, with time these problems were corrected.
The measure function of Google Earth shows length of equator to be 40030.24 kms but the actual length of the equator is about 40075.02 km. The error is about -0.112% which is negligible. On 16 December, Antarctica was updated to a resolution of 15 m using imagery from Landsat image mosaic. Arctic polar ice cap that is presently missing from current version of Google Earth will soon be added. Google Earth shows accurate details in most land areas.
The software also provides accurate information of military and other critical installations, thereby posing a threat to security. That is why Google Earth has been criticized by many special interest groups that include national officials. Serious concerns are expressed over high resolution pictures and images of sensitive locations that are easily available on Google Earth. Due to pressure from these sites, Google has decided to censor these sites.
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