Simon wrote: > This is my method too. I have converted before, but always > included > both maxspeed=* (~km/h) and maxspeed:mph=* (mph)
OK, I can see having (or allowing for) both of these makes some sort of sense, although it does lead to the situation where you might have two maxspeed tags for a way which might not even be close to agreeing (say if one user adds maxspeed:mph=30 at one time and someone later adds maxspeed=30 without specifying units anywhere). Users of the data would then need some sort of algorithm to try and determine which is most likely to be accurate, and I would suggest that may need to perhaps use knowledge of individual countries to know whether their limits are in mph or km/h anyway, so that would suggest country specific units wouldn't have been any extra issue in the first place. Certainly with the UK maxspeed data as it currently stands, it will need some sort of algorithm to try and work out what the maxspeed value represents. However, having changed my maxspeed=30mph tags to maxspeed:mph=30 and got the tiles rerendered, this still doesn't seem to help with the maplint not-in-map_features highlighting, and even if it did then it still probably wouldn't like maxspeed(with or without :mph)=national to mark roads that are at the national speed limit (I've not checked to see whether it copes with maxspeed=none as is recommended for relevant German autobahns, but I'd guess not, and I can see despite the suggestion to use it on the maxspeed wiki page [1], the proposal to formalise it currently seems to be being generally opposed [2]). Also, checking Tagwatch [0], maxspeed:mph=30 seems much less common than maxspeed=30mph so this does seem to be a minority choice for tagging, although could be added to Map Features easily enough as a numeric value and so not highlighted by Maplint. I guess this then means any other maxspeed:units should also be added. Does anyone use maxspeed:knots for example? I'm almost tempted to add maxspeed=30mph and maxspeed:mph=30 - just to be clear what the speed limit actually is <g>. I can see no point at all in putting a km/h speed limit value on a tag unless the sign is in km/h (and I believe I have read of a few in the UK). Surely it should be down to the users of the data to do the conversion of maxspeed at whatever accuracy they want, rather than making the people collecting the data calculate something other than that which is physically denoted on the signs, resulting in differing degrees of rounding which the user of the data would then have to guess means 30mph, effectively converting from estimate to accurate and back to desired accuracy. As long as the units are clearly expressed if they are not the default then this shouldn't be a problem (and I'm assuming no-one would read mph as metres per hour, except perhaps snails). Looking at the comments about maxspeed on the wiki at present, perhaps some consideration should be put towards some proposal, such as: maxspeed=number (optional units from predefined list, default km/h) maxspeed:opposite=number (optional units from predefined list, default km/h) maxspeed:psv=number (optional units etc) maxspeed:psv:opposite=number (optional etc) which would allow for where single ways have different speeds in opposite directions (I can't think of any examples, but someone asked about it on maxspeed discussion page), and where different vehicle types (I use psv only as one example) have different limits - I think it more common on things like the French toll routes than in the UK; in the UK some vehicle types have different limit, but that is a feature of the vehicle therefore and not something that needs mapping). I have suggested the optional units here be with the value as that avoids having multiple contradictory maxspeeds that differ only in the units specified; it is for this reason I was using maxspeed=30mph originally (rather than maxspeed:mph=30, as I had seen mention of both alternatives previously. I note though maxspeed=walk seems to be looking like it might get voted through [3], which wouldn't fit very well with the above. Ed [0] http://tagwatch.stoecker.eu/Great_britain/En/tags.html [1] http://wiki.openstreetmap.org/index.php/Key:maxspeed [2] http://wiki.openstreetmap.org/index.php/Proposed_features/maxspeed_none [3] http://wiki.openstreetmap.org/index.php/Proposed_features/maxspeed_walk _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
