Just as a quick test. How spatially accurate are the online map systems?
Reference
Google Maps 164.592m - Accurate ✓
Google Earth 163.99m - Accurate ✓
ESRI ArcGIS Online 164.7m - Accurate ✓
Bing Maps Unknown Distance (Map Distance App is no longer available).
From this view, it would appear that geo-registration and referencing of the imagery on the WGS84 datum is pretty accurate from the standpoint of Google and ESRI. Both ESRI and Bing are using the same imagery for this location in the world, but whether or not the Bing map is registered correctly to reflect the standard given in the first figure, remains to be seen.
A interesting journal article recently published in Cartographica 49:3, 2014, pp. 164–174, by Andrea Favretto, entitled Coordinate Questions in the Web Environment inspired this blog entry. In the article, Faveretto examines different projections and representations of earth in the digital mapping environments. He demonstrates some inconsistencies.
Here is one of his main figures (page 117) replicated for educational information here:
It would appear that in his examples there are problems with the distances and the registration. However, he does not give the statistical accuracy related to the reliability of the horizontal accuracy of the GPS unit that was used to create the points on image d in Figure 1. directly above.
It would appear that in his examples there are problems with the distances and the registration. However, he does not give the statistical accuracy related to the reliability of the horizontal accuracy of the GPS unit that was used to create the points on image d in Figure 1. directly above.
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