[HOT] Imagery alignment

Springfield Harrison stellargps at gmail.com
Mon May 4 07:56:54 UTC 2015

Thanks Helen, very challenging.  Are the underlying maps accurately
georeferenced?  If so, georeferencing the new imagery should not be too
difficult but not likely possible online.

Non of these shifts would be linear, especially in  areas of such high
relief. Are mappers just dragging the imagery around to fit by eye?  Are
there no GIS shops that could help with this?

Not sure if I can help further . . .

Cheers . . . . .   Spring Harrison
Samsung Tab 4
On May 4, 2015 12:38 AM, "Helen Tait" <helent55 at gmail.com> wrote:

> This is in reply to a previous question today (sorry I have not worked out
> how to reply to specific post).
> Archival imagery (such as Bing) has usually been processed and
> georeferenced/orthorectified (although to variable degrees depending on the
> source) prior to publishing. The post earthquake imagery provided by DG
> will have had minimal such processing undertaken on it as this takes time
> and effort and obviously DG want to just get the imagery out there for
> people to use ASAP.  Alignment of this imagery to existing map layers will
> not be a straightforward shift in one direction due to the effect of
> elevation/terrain and satellite capture angle.  My advice for this type of
> imagery would be to continually adjust the imagery to available/reliable
> map information as necessary - in one area of the image you may only need
> to adjust by say 10m to get a decent alignment - other areas may require a
> 100m shift. For the archival (e.g. Bing) imagery there can still be some
> alignment issues - this imagery will may have had systematic corrections
> but no manual input using ground control points (which is required for
> really accurate orthorectification).
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