OpenStreetMap

Observations during a HOT task

Posted by dcp on 14 March 2015 in English (English)

I recently did a little work (for the first time) on a HOT task 892 in Africa. It was the simple task of adding highways between the settlements. Using Bing imagery we were ask to mark the settlements as landuse=residential and the connections between as highways.

Easy enough you may say and yes it was apart from some poor imagery.

However, paths of about 1 meter width were traced with a higher category even up to highway=unclassified

Tracks of one vehicle width were also traced as highway=unclassified

The highways connecting the settlements were attached to the perimeter of the landuse=residential. Routing would be impossible.

I abided by the HOT instructions and used the landuse=residential but most of the settlements were small homesteads similar to landuse=farmyard. The tag landuse=homestead would have been more appropriate but we don’t have it.

It was also mentioned that locals on the ground would clean up the OSM data after we OSMers left but is that not being a bit unreasonable. These homesteads don’t even have tap water let alone an internet connection.

I shudder to think I would have to use this data for routing!

Comment from Sanderd17 on 14 March 2015 at 09:27

Quite often, you’d be surprised how wide paths actually are. Very often, treetops cover a big part of the path, but it’s perfectly possible to drive under the treetop with a vehicle.

It’s safe to assume that you can always reach a village with a car, so the most important trail leading to it should be at least highway=unclassified.

Connecting roads to residential areas is indeed no good practice, and it shouldn’t be the local’s job to finish this.

Comment from AndiG88 on 14 March 2015 at 14:02

highway=unclassified

I think the problem is that many people think this key means “I don’t know what kind of road this is”. Took me a long time to realize it’s not a placeholder. Just a very missleading wording for a tag.

Comment from zarl on 14 March 2015 at 15:17

Next to the description of the HOTOSM task is a tab “Instructions”. There you should find a link to a classification of roads more adapted to the context of African countries. I hope this answers your questions.

Comment from dcp on 14 March 2015 at 18:45

The width of the truck tracks were easily visible due to the two tyre markings. Yes, they did disappear under trees now and again but one can assume that if the tracks are identifiable for one sector then they they will carry on underneath the foliage.

IMHO if two vehicles travelling in opposite directions cannot pass each other without one of them going off-road then it should be defined as a track even if the HOT instructions state otherwise!

Paths of about 1 meter width were also identifiable as such and they often connected different homesteads.

On this HOT task, highway width could usually be measured in JOSM.

This is a personal opinion: If you cannot recognise the highway classification then you should default to the lower class.

Please remember that the probability that anyone corrects our HOT data inputs from a survey is pretty remote. These are vast areas with no OSM contributors on the ground.

Another data input which we were asked for was to identify potential helicopter landing pads (near the homesteads) and tag them with leisure=common. No information was available as to the minimum diameter (I asked). It was not possible to judge the slant but that is OK: The pilot has to make his own judgment.

Of course I complied but I don’t like the idea of entering data into the database that is wrong. Who is going to remove it? If the HOT team want this information then we should have a special tag for this purpose that can easily be globally removed. What I mean is something like:

hot_tag=helipad

expire_year=2016

Comment from AndiG88 on 14 March 2015 at 22:26

This is a personal opinion: If you cannot recognise the highway classification then you should default to the lower class.

Or you tag is as unclassified. Oh wait…

Comment from mcld on 14 March 2015 at 23:57

Hi - just a couple of responses:

Routing would be impossible.

In HOT tasks we do get a good proportion of enthusiastic newcomers, who sometimes don’t understand the routing aspect of mapping. It’s a job we have, to educate contributors. If you have the time, please feel free to send a (friendly!) message to the mapper who did that.

the probability that anyone corrects our HOT data inputs from a survey is pretty remote.

Not as remote as you might think: maybe it’s unlikely the locals will correct it, but some of the NGOs that actively use our mapping will do so.

IMHO if two vehicles travelling in opposite directions cannot pass each other without one of them going off-road then it should be defined as a track even if the HOT instructions state otherwise!

That doesn’t sound right. There are lots of countryside roads here in Britain where vehicles can’t pass each other, yet they’re definitely not tracks.

If you cannot recognise the highway classification then you should default to the lower class.

My opinion is that if you cannot decide the classification, you should use highway=road which means “Road with an unknown classification”.

Comment from dcp on 15 March 2015 at 09:19

Thanks to all of you for responding to my observations: You are a wonderful group and all your opinions are, of course, valid.

I did contact the newbies and they did positively respond.

It would be nice if some of the NGOs would give us some feedback on the quality of our efforts but I suppose they have higher priority tasks to do. That is why they are on the spot, sometimes risking their lives!

Comment from Tvali on 17 March 2015 at 06:57

Great work!

Comment from AndrewBuck on 22 March 2015 at 13:50

Just to clear up a bit of a misunderstanding about the helipads too. There is a tag aeroway=helipad for ‘proper’ helipads which we do use when appropriate. The leisure=common thing is being done because many small villages have a common area near them and this are can so happen to make a good place to land a helicopter, just like a soccer pitch or other large grassy area. So we are not tagging them incorrectly, rather we are tagging them correctly just the reason we are placing focus on them is their potential use for helicopters.

Regarding the size of the common areas, just map them as they actually are, and it will be up to anyone using them to assess their suitability for what they may want to land there. Also, another fringe benefit of having them mapped is even if they aren’t used as landing sites, they make great places to park a truck to distribute food/medical supplies, or hold a community education meeting, etc. So it is their ancillary uses that makes them initeresting to us at this particular time.

Hope this clears up the confusion. I know there was a lot of confusion about this tag.

-AndrewBuck

Comment from GO_OSM on 24 March 2015 at 17:06

Hello, I live in West Africa for some years now. Don’t bother about perfect road classification, as it does not match our experience of roads anyhow. A jungle road with some gravel is often seen as a “highway” by everyone. The condition varies extremely and a road can become unpassable in the rain season or for other reasons. Routing is the smallest problem and the data does not replace the need to ask locals about the road condition. Cars can always pass each other, even on a food path. My Defender can go through everything! The problem starts if some trucks get stuck in the mud. A local scene is developing slowly, but the people often have different problems. In Ghana we have e.g. in the moment 24h no electricity and then 12h electricity. Guido

Login to leave a comment