Brisbane Mappers,

I'm working on a hypothesis that there is a fairly consistent "landslip" in the high-resolution (zoom 17) Yahoo imagery in western Brisbane. If we can pin down the magnitude of the slip, we can then systematically apply a reverse correction whenever we map new areas from the imagery.

The hypothesis goes like this. If you look at the longitudes across western Brisbane, take the following values A, B1 and B2.

--- A --- ... --- B1 - B2 ---

Where
A = 152.866 E (west Redbank)
B1 = 152.965 E
B2 = 152.972 E (Inala, west Indooroopilly, Mitchelton, Strathpine)

West of A and east of B2, the imagery alignment seems fine (to within a handful of pixels, as compared to GPS trace logs).

Between A and B1 is the north-south "slip zone" of about one street width (fence to fence, maybe 20 metres) - i.e. the imagery is ~20m north of where it "should" be.

B1-B2 seems to be where the "fault line" lies - there seems to be a smooth graduation between the slip area to the west of B1 and the correct area to the east of B2.

I haven't worked out where the equivalent fault line area is through A, but we will probably find out where A1 and A2 is in due time.

More observations are of course desirable as I like to be proven right. (-:

Lat/Lon are of B1/B2 through Indooroopilly.