4 replies to this topic

[Bitmap]

Hi everyone,
my first post here so I hope this is in the right place.
I was wondering does anyone have information as to how accurate (at maximum magnification level) the contours on the Google terrain maps are and how they are derived?

[Charles Syrett]

Contours are derived from digital data, the accuracy of which varies considerably from one area to another. The accuracy of Google's elevations is just as variable as the accuracy of anything else displayed -- such as air photography (varies as to age and resolution), roads, buildings, etc. -- since it comes from many different sources.

Charles Syrett
Map Graphics
http://www.mapgraphics.com

[Bitmap]

Thanks for the prompt reply
I feared as much
I was hoping that the Google contours could be used to create accurate elevation models for Ireland in 3D modelling applications.
I guess it is back to the tedium of large scale O.S. maps.

[GIS xtra]

For height contours you can use 3o m ASTER or 90 m SRTM data

[EC2011]

The prior comments are correct -- digital data can be quite inexact. Sorry that there isn't a better solution.