[Talk-GB] tracing lakes with Potlatch

[Henry Gomersall]

On Tue, 2010-04-06 at 17:26 +0100, Jason Cunningham wrote:
> The detail for water is excellent and may be the most 'detailed'
> vector data OS is going to provide. It's far better than the OSM
> community could achieve with GPSr's and aerial image tracing.

Do you know how OS do the water detail? I've often wondered how they
manage to get such good detail of really tiny streams in the middle of
nowhere, often obscured by trees.

Looking at the second link, there are islands in the stream that are
marked on the map, but simply not visible on the aerial imagery. I
suspect ground imaging radar would highlight water, but surely this has
similar tree obscuring issues.

cheers,

Henry