[HOT] Validation

john whelan jwhelan0112 at gmail.com
Sun Aug 23 23:34:06 UTC 2015

I've been looking through the new courses and one thing that hit me was my
idea of validation seems quite different to the concept I've seen so far in
the course so I think we should start by deciding what we want our tile
validators to do.

These are my thoughts.

Higher level validation can use different tools over a wider area.

First comment is what I've found to be the most successful is not to
declare something invalid unless its really bad.  You want the mapper to
feel welcome, you want them to map again, INVALID missing a hut doesn't do
that.  I've had people send me that on one of my tiles by the way, just map
the hut and move on.

Generally I'll sit on one or more projects and validate just those projects
as the tiles are done.

The objective is to give feedback within 24 hrs or less to the mapper.

This feedback serves two purposes, one we are interested in your mapping
and second the earlier I can catch someone making a mistake the fewer
errors I'll need to fix in the future.

In Cameroon using these techniques we've actually managed to completely map
and validate several projects.

Note to Project managers if you want your project completed get yourself a
validator who validates the tiles as they are done.

When you start on a new project take a look at the mapper, if they've
mapped twice three months ago then don't waste your time sending them
emails just clean up.

Personally I only use JOSM when validating, you do have to press the
validate button for it to do its thing by the way.  It will only
automatically validate those edits you have made when you upload not the

Having said that there is a place for iD when validating, two of the
mappers I work with validate as a team one does the careful visual checking
in iD, the other runs JOSM over the end product.

The quality of the imagery used seems to have an impact on the quality of
the mapping.  Especially with new mappers, less than ideal imagery means
validation is slow and tedious.

I think we have to ask ourselves about how much we are prepared to pay for
what quality of work.  ie service level agreement.

When we have a very large number of new mappers who are making lots of
errors then sometimes the judgement call is a JOSM validation to clean up
the worst errors and tag it "validated in JOSM" so if someone has the time
they can go back over it.  Select two top tiles and two base tiles and
bring them into JOSM, now download the area between directly from OSM run
the validator tool and do the search checks, ie area=yes etc.  Its fast and
picks up many mistakes but isn't the same quality as a normal validation.

Things to look for are untagged ways - JOSM validation will pick these up.

area=yes can be landuse=residential or building=yes
zebra crossings in anywhere but the UK shouldn't be there.

crossing highways not connected, throws the routing software.

In Africa in rural areas highway=footway should be highway=path same for
highway=pedestrian, careful how you give feedback if they are an
experienced OSM mapper they're used to tagging with other values and you
want to retain them so point them to the African highway wiki bit and
suggest highway=unclassified, track or path are the most commonly used
values in rural areas.

Buildings not squared, select buildings=yes the select each mapper in turn
if the don't have any huts use q to square them all at once. This is a time
management issue if we had more time we should do them one at a time
reality does it really matter if the building is square?  We know the rough
shape and size and buildings are expensive in mapper time.  Locally talking
to one mapper, buildings are OK for the first three hours after that forget
them.  Another mapper I know refers them as building hell projects.  Some
mappers are very good and will map buildings, I tend to be protective of
them and very gentle with them as well.  If you have a building project the
ones mapped in JOSM building_tool are much easier to validate than the iD

Scan the tile <crtl><Down arrow> and look for missed settlements, I think
my record is twenty on a single tile.

huts are awkward, OSM says point or circular, HOT prefers circular but
experienced mappers will often use points.  You want them to keep HOT
mapping, if you criticise them too much they'll go back and map waste paper
bins locally.

Is there some sort of path or unclassified highway to each settlement?  If
not can we drop one in.  I map fewer paths, and tracks than I used to, it
takes time to map every track and path.

Try to avoid being condescending when communicating with mappers.   "The
content is great, but how things are said often leaves the impression we
are a bunch of arrogant, condescending jerks." Each mapper is different,
you won't have time to read their life history before contacting them,
click on their name the OSM profile send message or @username (@[firstname
secondname] if they have a space in their name) in the comment.  the @
method works best as it shows the project and tile numbers.  Be polite and
if possible use the third person, JOSM validation threw up the following
problems on this tile.  HOT may not have their email address but you can
contact them, the OSM profile will send an email to their email address.

If they are carefully mapping every building on the project and it isn't
required in the instructions I tend to say thanks for mapping them but they
aren't required in the instructions, hoping they'll map a few more tiles
more quickly.

Somethings are subjective, if one mapper has mapped them one way on one
tile and another mapper has mapped them differently on another unless there
is a clear way to map them I'd let them go.  For example
highway=unclassified or highway=path sometimes its difficult to be definite
one way or the other especially when you look at the number of buildings in
the settlement.

I do do a <crtl>f with nothing in it to select everything then scroll down
the list of tags looking for unusual ones.

Finally I never use JOSM Presets <crtl>f works fine for me.

I'm sure others have different ways of validating so your thoughts please
then perhaps we can first define our target audience then refine the course.

Cheerio John
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/hot/attachments/20150823/281da849/attachment.html>

More information about the HOT mailing list