The National Geospatial Intelligence Agency has released the following advisory about the use of Web Mercator map projection: http://earth-info.nima.mil/GandG/wgs84/web_mercator/
While Web Mercator is quite useful for web map services by dividing the earth into perfectly square tiles regardless of map scale, it was not intended for navigation or high-accuracy mapping. Even before this NGA advisory was released, I had been concerned about relying on tools like Mission Planner that use web map services such as Google & Bing. I do flight plan edits in commercial GIS software because there's more control over reference systems & the ability to use higher quality datasets.
I'm curious to know if anyone else is using alternative methods for flight planning. Or am I simply mistaken in assuming that Mission Planner does not reproject into the WGS 84 based reference system?
Replies
It's not about the short distances, but rather where on the globe you are. Distortions will be greater for areas farther from the equator. That's why local reference systems like UTM or state plane are more appropriate for measurements. Here's another article that describes why Web Mercator shouldn't be used for measuring distances and areas:
http://blogs.esri.com/esri/arcgis/2010/03/05/measuring-distances-an...
And here's another article that illustrates different projections of WGS 1984:
http://support.esri.com/cn/knowledgebase/techarticles/detail/39404