Proposal talk:Speed limit string values for Romania

[Vlad Bailescu] Against! The focus should be on quality of data, not quantity; especially if data is easily deducted from existing information (street category and administrative bounds). Restrictions are useful for street sectors where we have a specific speed limit.

I'm not sure how "data is easily deducted from existing information" if you have a big map like Europe map. Please give few details. Flaviu 08:00, 9 December 2010 (UTC)

Intersect polyline with bounds polygons and calculate speed based on street/road category and vehicle type. This is easy. A PostgreSQL + PostGIS function will do this for a street segment in milliseconds on decent hardware with the whole planet loaded into the DB.

The real question is: What do YOU want to do with the data?

I'll give two quick examples:

1. You want to do routing EFFICIENTLY: then you need to transform the data from OSM into a graph with associated costs for each arc. To calculate the costs you will need to factor in the max speed and road conditions. This is a one time operation (repeated for each update of the routing data) and it's more important to have correct information (road category, precise administrative boundaries) that to save a bit of time by having the speed explicitely defined for each street segment. You will have to implement logic to deduct the max speed anyway for the segments that are missing the explicit max speed.

2. You want to display speed limit on a rendered map (ie tiles)? Best mapping practice is to put on the map only exceptions to well-know rules (in order to keep it as uncluttered as possible). So the rendering should at max show the explicit restrictions (road signs). If you want to query the max speed for a certain segment you should do that as a separate service. If we're talking about web maps, the best would be to use AJAX, ie the user clicks on the map and a request is sent to a server

For other purposes, everyone is free to process the hell out of the data. But if the main source is clean and normalized, it will help everyone. Vlad

Currently I only want to obtain in the most simple and efficient way the speed limit for each way. I think is much easier to read maxspeed tags from OSM map than:

1. Maintain a DB,
2. Import the whole OSM data into DB,
3. Find out the max speed for each way using spatial operations. How many spatial queries has to be done for each way? How much time it takes to a deduct a maxspeed value?

Is this whole work and time spent worth than adding few megabytes to the OSM map (for example 44 MB it's enough to add to all navigable ways from Romania map 2 maxspeed tags for motorcars and HGVs)?

Each time you process an updated map the total time spent by you making maps is increasing but your life span is not increasing. Having set maxspeed tags for each way (you can consider it precalculated) free all of us of the burden of the maxspeed deduction and the time lost with that. If there are some data in the OSM you consider not important, you can skip it very simple from the XML parser. But I don't like to be forced to spent resources if I could obtain what I need in a straightforward and costless way. Why we should be irrational? Flaviu 15:18, 9 December 2010 (UTC)

It would be really nice if you can upload back to the OSM server the deduced values of maxspeed and all of us will benefit including you because next time when you will process updated maps you will have the maxspeed already calculated. This is altruism and it is related the the OSM phenomenon. -- Flaviu 15:41, 9 December 2010 (UTC)

You asked for an opinion, you got it. I don't consider I need to justify anymore - this discussion is lifetime I'm not getting back, the data processing is done automatically by a script running on a server. I don't want to demotivate you but I think it's wasted time to add the tags to OSM XML. But then again, it's your time. If YOU need this data so badly, go ahead and add the tags, I hope the local community is clever enough not to start an edit war over this topic!--Vlad 07:49, 10 December 2010 (UTC)

You said "Against!" but no clear reason! I have no script running on a server, I don't have a server, I have only romania.osm (1.6 GB). My reason to add those tags is very good for the benefit of all community but it seems there are only selfish economic interests. -- Flaviu 09:03, 10 December 2010 (UTC)

Salut, scuze ca ma bag si eu, sunt nou pe aici, dar din cate inteleg unele date nu sunt disponibile pentru toti. Mi se pare cam ciudat sa existe membrii dintr-o comunitate open source care sa fie privilegiati. E open source sau nu?

[Octavian Chelu] La ce date te referi? Oricum nu ai nimerit unde trebuie aici se discuta altceva. Primești răspunsuri mai repede dacă te înscrii pe talk-ro@openstreetmap.org

Nu, nu e vorba de open source. E doar vorba că cei care au investit resurse se descurcă determinând maxspeed, restul nu. Flaviu 05:59, 10 December 2010 (UTC)

Datele sunt aceleasi pentru toti, e treaba fiecaruia ce vrea sa faca si cum cu ele.--Vlad 07:49, 10 December 2010 (UTC)

[Cristian Draghici] I am against any redundant data. The "is_in" tag is in my opinion redundant because it contains data that can be easily computed based on "boundary=administrative" and "admin_level=x". The same principle applies to generic speed restrictions so I would rather see effort invested in correctly defining administrative boundaries that permit spatial queries.

If the spatial queries (or something else) are not available/affordable for everyone, it is not correct to say that the results of such operations are redundant (those results are not available for everyone). -- Flaviu 15:46, 30 December 2010 (UTC)

numbers + source:maxspeed

As dicussed on for example Talk:Key:maxspeed it's more in line with the conventions to always enter (if the mapper does care about the maxspeed enough to map it) the numeric maxspeed (or two where the hgv speed is lower), and possibly add source:maxspeed=RO:urban/RO:.... And think about it this way: the maxspeed follows from the legal classification, but the maxspeed is not a "RO:urban". Sure, document on OSM_tags_for_routing/Maxspeed if you have reasonable defaults for a translation highway=* -> maxspeed=*. Alv 14:19, 1 January 2011 (UTC)

Hi, I replied on Talk:Key:maxspeed#numbers_.2B_source:maxspeed. Flaviu 14:22, 4 January 2011 (UTC)