[OSM-talk] Announcement: Availability of True Offset web service

Steve Bennett stevagewp at gmail.com
Fri Feb 18 04:08:04 GMT 2011

On Fri, Feb 18, 2011 at 11:21 AM, Dermot McNally <dermotm at gmail.com> wrote:
> In exactly the same way as, say, the Offset bookmarks offered by JOSM
> - it doesn't, and the mapper needs to notice that the imagery doesn't
> seem to line up any more. As such, as a baseline, using True Offset is
> at worst no worse than other options for managing your calibration.

For imagery sources like NearMap*, which support a time dimension,
maybe it's worth including some kind of date field? That would also be
helpful for imagery that, even if you can't access older imagery, can
at least tell you the date of the current stuff, so you'd know if the
offset was out of date. Relying on a "mapper to notice that the
imagery doesn't seem to line up" seems to defeat the purpose of the
whole thing a bit, in my eyes.

And yes, it is worse, because mappers could end up applying a false
offset. and not knowing. Say Bing had some imagery which was out by
20m for a large rural area. Someone applies the offset, and starts
mapping. Then Bing fixes its imagery. Someone else comes along and
maps in an area with not much to reference against, and now their
mapping is all offset...

Is there a way for the service to check when changes are made to the
imagery provider, and reset all offsets?

* (Not that NearMap in practice actually has any offset worth recording...)

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