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

Ben Last ben.last at nearmap.com
Fri Feb 18 00:08:35 GMT 2011

Quick question; how does this cope with updates to aerial/satellite imagery
that may change the offset for a given service at a given location?

On 18 February 2011 07:47, Dermot McNally <dermotm at gmail.com> wrote:

> Hi,
> Many of you will have followed earlier discussions of the True Offset
> process, intended to solve as simply as possible the problem of
> imagery offsets by enabling editors to, by default, calibrate
> background imagery based on offset data managed by mappers. In this
> way, inexperienced mappers or people tracing without local knowledge
> can avoid polluting the map with badly offset contributions.
> The service is now live and seems to be working well on the dev server
> and I have updated the wiki page to reflect this and some late
> changes:
> http://wiki.openstreetmap.org/wiki/True_Offset_Process
> The highlights:
> * You can try it at:
> http://mackerski.dev.openstreetmap.org/offset/1.0/offset/bing/20/53.26/-6.67
> * I have re-documented the meanings of the offset northing and easting
> to ensure compatibility in units and sign with the offset bookmarks
> already exposed by the JOSM Imagery module.
> * This restatement of meaning may lead to a sign shift for one or
> other of the values. So if you have previously entered offset data for
> consumption by True Offset, please check that it is still correct.
> This goes doubly for anybody who recorded offsets based on the
> earliest proposals which used metres instead of degrees.
> * Offset Database updates are currently manual (this will change). So
> for now, if you add or change some offset data, please let me know so
> I can cause it to take effect.
> * Most of my test offset data has been for Bing imagery in Ireland.
> Until the next database update, some of these may be inaccurate.
> My appeal: If you are a developer of one of the OSM editors that
> supports background imagery layers, PLEASE build support for True
> Offset, and please have your editors either apply the corrections
> silently by default or at the very least prompt users that a known
> offset exists and offer to use it. While I hope True Offset is useful
> to experienced mappers who already calibrate their imagery, its real
> purpose is to avoid the destructive effect of tracing mappers who
> don't even realise they can or should calibrate.
> Happy Mapping!
> Dermot
> --
> --------------------------------------
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Ben Last
Development Manager
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