[talk-ph] Advanced imagery alignment with Imagery Offsets DB

Erwin Olario govvin at gmail.com
Fri Aug 3 03:03:32 UTC 2018

Earlier this week, the OSM data team of Grab posted an email [0]about their
plan to address issues [1] they found in NCR, which has led to a discussion
about the Imagery Offsets Database (IODb) [2] because of a statement in
their ticket that (they) "would be using Bing imagery **without any offset
**while correcting existing network and/or add missing roads" (emphasis in
mine) , but that phrase was nowhere in their email to the mailing list.

The Grab team has been quite responsive in the past, to address the
concerns we've had with them and they are still that to this day. Kudos
Grab team!

Eugene made note of the vague description of their task and asked them to
elaborate, which they did [3] and they also identified the specific objects
they plan to work on.

The ensuing conversations, however, were in the OpenStreetMap Asia's
Telegram channel [4], and so they were asked to pursue the detailed
discussion in this list to make the rest of the discussions public, and
accessible to the rest of the community.

To restart the conversation, I'll respond to the query [5] made by Lavanya
regarding the Imagery Offsets plugin for JOSM.  ( If you're new with that
plugin, this short introduction [6] will help you get started. )

In a later image they posted [7] on Telegram which they described as
"conflicting" with the image label: "offset in josm for same location 3m" ,
they appear to have misinterpreted distance of the location where the
offsets adjustments were set ("296m" east of their current location) and
the actual offset distance ("3m") that has led to their conclusion that it
was "conflicting".

Back on my desk, I replicated their JOSM setup to get a clearer image, and
as seen in this screen cap [11], the record actually match with what was
found in the offset record in question [9].  Therefore, there's no actual

The offset in question [9] was made by Rally during the course of our work
with the NCR road alignment validation with Kaart [10] that was completed
in June.

I believe the image [12] found in the quick start page for the plugin are
very helpful in describing the plugin's GUI elements.

The IODb is a great resource for JOSM and Vespucci editors, but is not yet
supported by iD. For iD users, the accepted convention is to adjust the
aerial imagery to the offsets used in the edits you find in the area. This
will make it easier for future edits to "fix" the objects, when a more
accurate imagery alignment has been made with the use of Strava or other
SatNav tracks.


[1]: https://github.com/GRABOSM/Grab-Data/issues/19
[2]: http://offsets.textual.ru/
[3]: https://github.com/GRABOSM/Grab-Data/issues/19#issuecomment-409813382
[4]: https://t.me/joinchat/DDHaxw_VjhJAb-vITJnWRQ
[5]: https://t.me/OpenStreetMapAsia/1254
[7]: https://t.me/OpenStreetMapAsia/1259
[8]: https://t.me/OpenStreetMapAsia/1257
[9]: http://imgur.com/xjvNNDTl.png
[10]: https://github.com/KaartGroup/Philippines/issues/12
[11]: http://imgur.com/Y04krKtl.png <http://imgur.com/oVHZRiAl.png>


/Erwin Olario

e: erwin at ngnuity.xyz | v/m: https://t.me/GOwin | s: https://mstdn.io/@GOwin
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