[HOT] Validation queries

Pierre Béland pierzenh at yahoo.fr
Wed Jan 15 14:39:13 UTC 2014

I Theodin,

It is true that every new crisis mobilizes the contributors. At the same time, there is some work left to contribute in other places. The Philippines crisis revealed how our community is growing and have the capacity to respond rapidly to such major crisis. This was after Democratic Republic of Congo, Mali Activations and various other projects the HOT and OSM community responded to (ie. Madagascar, Indonesia, Philiipines other then Haiyan, North India, etc).  If we add all the projects in 2013, the picture shows a significant progress in the response to the various crisis.

At the same time, this is true that we should take care the other crisis were the media spotlights are not. Local communities, university students could take the initiative to organize groups and take care of various other areas that need some care with mapping, validation, road classification, etc.

I invite the contributors to look at the Task Manager jobs for South Sudan and Central African Republic where the humanitarians need some support from the mapping community.  In Norh of Mal, there is reconstruction after last year civil war and some TM jobs need some care since there are still large areas not covered. Democratic Republic of Congo is an other area where we plan to add some mapping while new images will come. 


 De : Theodin <theodin at posteo.de>
À : hot at openstreetmap.org 
Envoyé le : Mercredi 15 janvier 2014 5h21
Objet : Re: [HOT] Validation queries

Hi Severin and all others,

Although I practically stopped working on OSM in CAR, I am still
    following the list and read your Wiki-page-style how-to with
    interest (reading it I realised I didnt make any of the errors you
    mentioned which is nice :) ). I hope to be able to contribute more
    in the coming months. Its nice to see so many people emergency-map
    for OSM (Yolanda etc), and I hope some will start to work on other
    areas as well which are hit badly by crises of a not-so-obvious


Am 14.01.2014 19:24, schrieb Severin MENARD:

Hi Nick,
>Thank you for your email. My answers inline.
>Date: Sun, 12 Jan 2014 13:48:00 +0000
>>From: Nick Allen <nick.allen.54 at gmail.com>
>>To: HOT at openstreetmap.org
>>Subject: [HOT] Validation queries
>>Message-ID: <52D29D10.6010009 at gmail.com>
>>Content-Type: text/plain; charset="iso-8859-1";
>>Would you like me to join in with the validation process?
              I am
>>experienced in mapping OSM, but am fairly new to regularly
              mapping HOT
>Would be great! Thanks for the proposition! Indeed you have contributed a lot in OSM. Mapping HOT projects is not very complicated, as you saw with the Highway_Tag_Africa, it is less detailed then in developed countries, at least regarding remote mapping. Maybe the difficulty is when you do not know how those contexts look like. A goo way to compensate this is to look for videos posted on Youtube (examples here), especially the ones taken along road or streets. This is how you figure out if properties enclosures are walls, fences or hedges, what is often a cultural feature. Ah, just saw you mapped some wall enclosures (eg here). They actually are buildings (houses) under construction. It is frequent in developing countries that such works last a long time or even be abandoned. 
>>I'm responsible for some of the mapping in
>>http://tasks.hotosm.org/job/72, as well as trying to change some of the
>>more obvious 'highway=track to highway=residential or
              unclassified etc..
>>or it may be easier to check what I've done using my OSM
>>How much validation is actually needed / done? Is it a
              proportion of the
>>whole task, or just until you are confident that, all
              things considered,
>>the task is fulfilled? You're never going to get 100% as
              some things
>>boil down to opinion about what the images actually are
              of, but the vast
>>proportion is pretty obvious.
>This is something that still needs to be settled and documented. I would say a validation is about both identifying mistakes/mapping lacks and standarzation/consolidation and has 2 or three steps, related to scale:
>1. At neighborhood scale, check notably if:
>	* buildings are missing. Sometimes it happens and if actually it represents a consequent number of building over a TM task, it can be invalidated
>	* buildings are correctly traced. Hopefully it is not frequent, but sometimes mappers made really coarse outlines that do not respect either the buildings proportions or angle. More frequent are mappers that do not know how to square the buildings. In this case, after having checked what is their preferred editor, I generally send a message to their OSM message box to give them the tip to do it
>	* highway tags are correct. This is what you described. Some mappers put tracks wherever it is not a main road considering it is not paved, but this is not a meaningful criteria in these developing countries considering 99% of roads are unpaved. 
>	* road geometry. Some mappers do not put enough details and other too much (eg a node every 10 or 20 m even if the road is straight). First case is quickly corrected with the (magical) Improve Way Accuracy mode in JOSM; second case requires deleting extra nodes when they actually make weave a straight road. 
>	* start/end of roads. Some mappers are experts of giant snake roads or loop roads, Requires to pass the mouse over the streets to see their extent and cut them where it makes sense. On the contrary, some streets or roads are sawed without any reason (same tags for all the sections)
>	* general issues of connections between objects. Some that should be connected and those that should not. Requires both Validator and also eye control
> 2. at the town or city scale, it is quite related to the road network and its main highways. Having a larger view  to identify the highways that are not simple residential roads. They are often larger and frame a larger area or can be a parallel way to main roads. It is also important to check where they start and when they stop, what is often not possible to do when you map with the Tasking Manager. This is what I tried to do with Bouar; here are some examples of issues for Bangui:
>	* missing parts of highway. Looks weird on Mapnik and the check of the imagery confirms the two sides of the road separated by a drain are not finished
>	* road continuity. The situation here seems weird as well as we expect the 2 unclassified roads to be connected and not joined by a simple path. The imagery confirms that the southern highway looks the same, and should be tagged the same, whatever the tag. The example is actually good as farther south, it changes for tertiary. No reason for this, says the imagery. It should be cut when it becomes a straight road, though
>	* isolated upper-level road sections. Drivable highways cannot be isolated and connected to the drivable road network by paths, they must be connected to it
>	* tagging coherence. in this example, the primary and tertiary road are connected by a unclassified road. Same thing between the two tertiary roads. After having checked the imagery this road would deserve to be tagged as tertiary. This obvious example apart, this requires to check the streets width to identify the main ones that needs not to be tagged as residential but unclassified or even tertiary.
>Hope this can help! I had in mind to give some tips and it became a start for a future wikipage :) Hope other people will read/discuss/complete this.
>Any constructive feedback from experienced HOT mappers is welcomed.
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