[Tagging] surface=ground/dirt/earth

Fernando Trebien fernando.trebien at gmail.com
Wed Mar 19 23:10:47 UTC 2014

I think you mean that we should redefine the meaning of the values of
the tracktype tag. I'm wondering if that's good because the text has
been essentially stable since december 2011, when the article got its
head paragraphs. Descriptions of tag values have been essentially the
same since 2008, when the article was created. They've been only
slightly modified to reflect different "degrees of compaction". That's
simply a descriptive refinement to me. Check it out:

A majority of users not following the wiki could be a good reason to
change the definition, but did you notice anything like that in
practice, perhaps in Australia?

The descriptions you provide are actually very informative to me as
I'm trying to provide OSRM with reasonable default speeds for those
tags. I'd like to know:
- why would you need an SUV for grade6: is it too bumpy, or too likely
to bog, or either?
- can you travel through grade8 at all? with which kind of vehicle? is
it related to traction on loose surface, or is it related to clearance
and wheel size required to cross over an irregular terrain?

In a way, I think your descriptions are more subjective than what we
have in the wiki today for tracktype. Say grade4:
- wiki: "Mostly soft. Almost always an unpaved track prominently with
soil/sand/grass, but with some hard materials, or compressed materials
mixed in."
- you: "Sort of road you may prefer to go around if you can."

Why would one prefer to go around?, I wonder. If we're mapping what's
on the ground, we need a a clear and objective reason (something you
can see, test or measure) to prefer to go around. If we map that
reason, then applications can decide if that reason is significant for
their particular situation. The application could be calculating a
route for an SUV or for a motorcycle, there are many reasons with
totally different consequences for these vehicles, such as specific
surface shapes, material densities, and degree of slipperiness.

For grade1, you mention "OK, its unsealed but smooth, level, well
looked after". That's probably the same as smoothness=good/excellent.
Some of your other definitions seem to be overlapping with the
definition of smoothness too (when you mention "holes", "something
that will worry a city driver", "requires considerable care"), whereas
the current text in the wiki mostly doesn't (any combination of the
two tags is possible). If we can't eliminate one of the tags, then
it's best if they are as independent from each other as possible.

I'm all in favour of thinking about risky situations that should be
mapped and accounted for in apps (such as Mapnik/Carto and OsmAnd and
OSRM and MapQuest's and all the others). I'm wondering if you find
smoothness inadequate for what you want to accomplish, and why.
(Here's a good one, but the only one I know of:

On Tue, Mar 18, 2014 at 7:36 PM, David Bannon <dbannon at internode.on.net> wrote:
> Yes Dave (Swarthout), I share your views here. I'd rather we looked at a
> rating that reflected how well maintained and usable the road is likely
> to be. That is what most road users want to know. "Should I use this
> road or not ?"
> tracktype= does claim to use that approach and that why its so popular.
> Lets not move it into a purely descriptive model by defining the degree
> of sand, bog, pot holes, slipperyness, steepness, angle, corrigations
> etc ! If we take away that desirable "subjectivness" (there, I said it!)
> from tracktype= people will have to go off and invent yet another tag
> that says what they want and says what the map user wants.
> Please lets think of tracktype= as -
> 1. OK, its unsealed but smooth, level, well looked after.
> 2. Bit dodgy but almost any car (etc) will be fine if you slow down.
> 3. Likely to have holes, bogs, sand or something that will worry a city
> driver.
> 4. Sort of road you may prefer to go around if you can.
> 5. Requires considerable care, watch for the unexpected.
> And yes Dave, I am a big fan of extra grades to tracktype=
> 6. You probably should consider a SUV/4wd but experience will do.
> 7. A reasonable 4wd is probably required.
> 8. This is silly, a heavily modified 4wd is necessary. Take a film crew.
> All right, just a bit tongue in cheek but you see what I mean.
> David
> On Tue, 2014-03-18 at 12:14 +0700, Dave Swarthout wrote:
>> Yes, I agree firmness works better than stiffness for describing a
>> surface. I still would prefer a term that better characterizes what
>> Fernando said above: "To me, the idea [of] a firm/soft mixture seems
>> closely related to "how well maintained" the track/road is, as
>> mixtures that are not so durable/steady/firm quickly wear down and
>> look 'poorly maintained'."
>> A poorly maintained road, or one that is not well engineered, or one
>> composed of loose, uncompacted materials will be much less durable
>> than one that has those characteristics. Consequently, I still think
>> durability fits the bill. I hesitate to bring this up but the
>> discussion about trafficability tried to rationalize the relationship
>> between a highway's surface, hardness, composition and smoothness and
>> ran into similar problems (David Bannon?)
>> FWIW, borrowing again from Fernando above I would reword the
>> definitions as so:
>> grade1: "heavily compacted hardcore"
>> grade1: [Usually paved. If unpaved then a heavily compacted mixture of
>> materials (gravel, sand, earth, clay) that provide a fairly smooth,
>> durable and relatively weather-resistant surface.]
>> grade2: "unpaved (...) surface of gravel [a hard material] mixed with
>> varying amount of [soft materials] sand, silt and clay"
>> grade2: [Unpaved (...) surface of gravel mixed with a varying amount
>> of other materials and lightly compacted or rolled to provide a good
>> surface. Less durable or weather resistant than a grade1 track.]
>> grade3: "even mixture of hard and soft materials"
>> grade3" [Almost always an unpaved dirt road. A mixture of uncompacted
>> hard and soft materials providing a reasonable surface. Subject to
>> moderate degradation in bad weather. ]
>> grade4: "prominently with soil/sand/grass [soft materials], but
>> with some hard materials"
>> grade4: [A rougher unpaved dirt road with a mostly soft surface,
>> poorly maintained and not very durable. Rain and other bad weather
>> degrade this type of track rapidly.]
>> grade5: "lacking hard materials"
>> grade5: [A very rough unpaved track composed of loose, uncompacted,
>> soft materials often having a surface of grass and dirt, or, in wet
>> weather, mud. Not very durable -- easily eroded.]
>> Other OSMers have amended this list to include grade6 and even grade7
>> for tracks passable by 4WD or ATV only. What about those?
>> On Tue, Mar 18, 2014 at 8:57 AM, Fernando Trebien
>> <fernando.trebien at gmail.com> wrote:
>>         "Firmness" sounds good to me:
>>         http://www.merriam-webster.com/dictionary/firmness
>>         I know that "soundness" means the same but has some additional
>>         meanings
>>         (http://www.merriam-webster.com/dictionary/soundness),
>>         "firmness" is more specific.
>>         On Mon, Mar 17, 2014 at 9:09 PM, johnw <johnw at mac.com> wrote:
>>         >
>>         >
>>         >
>>         > On Mar 18, 2014, at 1:35 AM, Fernando Trebien
>>         <fernando.trebien at gmail.com>
>>         > wrote:
>>         >
>>         >  Replacing 'stiffness'
>>         > with something else is absolutely fine with me.
>>         >
>>         >
>>         >
>>         > What about firmness? soundness?
>>         >
>>         >
>>         > Javbw
>>         >
>>         > _______________________________________________
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>>         --
>>         Fernando Trebien
>>         +55 (51) 9962-5409
>>         "The speed of computer chips doubles every 18
>>         months." (Moore's law)
>>         "The speed of software halves every 18 months." (Gates' law)
>>         _______________________________________________
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>> --
>> Dave Swarthout
>> Homer, Alaska
>> Chiang Mai, Thailand
>> Travel Blog at http://dswarthout.blogspot.com
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Fernando Trebien
+55 (51) 9962-5409

"The speed of computer chips doubles every 18 months." (Moore's law)
"The speed of software halves every 18 months." (Gates' law)

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