Relation in multiple way

[mytracks]

Hi.

I am currently investigating the new feature to evaluate relations. I want to extract bus and tram routes. I created a relation_scan_function and accept all "route" tags. Within the way_function I am iterating over the relations using way:NextRelation. Generally this works. However, the ways have at most one relation. But in case of bus or tram lines this is different because one way may be part of various routes.

My question is whether this use-case is already supported. If it helps I can provide the Lua code.

Dirk

[systemed]

Code would be helpful - yes please!

[mytracks]

Here is the Lua code:

-- nodes to be processed
node_keys = { "highway", "railway" }

-- node attributes to be copied
node_attributes = { "name", "bicycle", "foot", "access", "smoothness", "surface", "type", "bridge", "tunnel", "route", "network", "cycle_network", "roundtrip", "icn_ref", "lcn_ref", "rcn_ref", "ncn_ref" }

-- way attributes to be copied
way_attributes = { "name", "bicycle", "foot", "access", "smoothness", "surface", "type", "bridge", "tunnel" }

-- route attributes to be copied
route_attributes = { "name", "colour", "operator", "lcn", "lcn_ref", "icn", "icn_ref", "rcn", "rcn_ref", "ncn", "ncn_ref", "ref" }

function init_function()
end

function exit_function()
end

function TrySetAttribute(obj, name)
	local value = obj:Find(name)
	if value~="" then
		obj:Attribute(name, value)
	end
end

-- try to read attribute from relation and add it to the way object.
-- concatenates the strings if the way object already contains the attribute
function TrySetRelationAttribute(way, rel_name, way_name)
	local value = way:FindInRelation(rel_name)
	if value~="" then
		local way_value = way:Find(way_name)
		if way_value~="" then
			way_value = way_value..";"..value
		else
			way_value = value
		end
		way:Attribute(way_name, way_value)
	end
end

function FindTag(obj, tags)
	for _,tag in pairs(tags) do
		local value = obj:Find(tag)
		if value~="" then
			return tag, value
		end
	end

	return nil, nil
end

function node_function(node)
	-- check whether highway or railway tag exists
	local obj_type, obj = FindTag(node, {"highway", "railway"})
	if obj_type~=nil then
		node:Layer("route", false)
		node:Attribute("obj_type", obj_type)
		node:Attribute("class", obj)

		-- copy attributes
		for _,attr in pairs(node_attributes) do
			TrySetAttribute(node, attr)
		end
	end
end

function way_function(way)
	-- check whether highway or railway tag exists
	local obj_type, obj = FindTag(way, {"highway", "railway"})
	if obj_type~=nil then
		way:Layer("route", false)
		way:Attribute(obj_type.."_class", obj)

		-- copy attributes
		for _,attr in pairs(way_attributes) do
			TrySetAttribute(way, obj_type.."_"..attr)
		end

		-- iterate of relations in order to copy attributes
		while true do
			local rel = way:NextRelation()
			if not rel then break end

			-- read the type of route, such as 'bicycle'
			local route = way:FindInRelation("route")

			if route~="" then
				way:Attribute(route.."_route", "yes")

				-- copy attributes from relations to the way 
				for _,attr in pairs(route_attributes) do
					TrySetRelationAttribute(way, attr, route.."_"..attr)
				end		
			end
		end
	end
end

function relation_scan_function(relation)
	if relation:Find("type")=="route" then
		local ref = relation:Find("ref")

		if ref~="" then
			-- accept all routes with a ref number
			relation:Accept()
		end
	end
end

[mytracks]

Yes, the attribute would be overwritten. That is true. But the problem is that I do not get more than one relation per way.

For debug reasons I used the following code inside the way_function:

		local count = 0
		while true do
			local rel = way:NextRelation()
			if not rel then break end

			count = count + 1
			if count > 1 then
				print("MULTIPLE RELATIONS")
			end
                end

But the debug text is never printed. I am pretty sure that my input data contains various ways belonging to the same relation. You can download the osm.pbf file here.

[mytracks]

Just to be sure I adapted the code so that I first collect all attributes from all relations within a dictionary:

-- nodes to be processed
node_keys = { "highway", "railway" }

-- node attributes to be copied
node_attributes = { "name", "bicycle", "foot", "access", "smoothness", "surface", "type", "bridge", "tunnel", "route", "network", "cycle_network", "roundtrip", "icn_ref", "lcn_ref", "rcn_ref", "ncn_ref" }

-- way attributes to be copied
way_attributes = { "name", "bicycle", "foot", "access", "smoothness", "surface", "type", "bridge", "tunnel" }

-- route attributes to be copied
route_attributes = { "name", "colour", "operator", "lcn", "lcn_ref", "icn", "icn_ref", "rcn", "rcn_ref", "ncn", "ncn_ref", "ref" }

function init_function()
end

function exit_function()
end

function TrySetAttribute(obj, source, target)
	local value = obj:Find(source)
	if value~="" then
		obj:Attribute(target, value)
	end
end

function FindTag(obj, tags)
	for _,tag in pairs(tags) do
		local value = obj:Find(tag)
		if value~="" then
			return tag, value
		end
	end

	return nil, nil
end

function node_function(node)
	-- check whether highway or railway tag exists
	local obj_type, obj = FindTag(node, {"highway", "railway"})
	if obj_type~=nil then
		node:Layer("route", false)
		node:Attribute("obj_type", obj_type)
		node:Attribute("class", obj)

		-- copy attributes
		for _,attr in pairs(node_attributes) do
			TrySetAttribute(node, attr, attr)
		end
	end
end

function way_function(way)
	-- check whether highway or railway tag exists
	local obj_type, obj = FindTag(way, {"highway", "railway"})
	if obj_type~=nil then
		way:Layer("route", false)
		way:Attribute(obj_type.."_class", obj)

		-- copy attributes
		for _,attr in pairs(way_attributes) do
			TrySetAttribute(way, attr, obj_type.."_"..attr)
		end

		-- iterate of relations in order to copy attributes
		local attributes = {} -- dictionary with attributes from all relations
		while true do
			local rel = way:NextRelation()
			if not rel then break end

			-- read the type of route, such as 'bicycle'
			local route = way:FindInRelation("route")

			if route~="" then
				way:Attribute(route.."_route", "yes")

				-- copy attributes from relations to the dictionary 
				for _,attr in pairs(route_attributes) do
					local way_name = route.."_"..attr
					local value = way:FindInRelation(attr)

					if attributes[way_name] ~= nil then
						attributes[way_name] = attributes[way_name].."; "..value
						print("MULTIPLE RELATIONS")
					else
						attributes[way_name] = value
					end
				end		
			end
		end

		-- copy attributes from dictionary to the way object
		for attr,value in pairs(attributes) do
			if value ~= "" then
				way:Attribute(attr, value)
			end
		end
	end
end

function relation_scan_function(relation)
	if relation:Find("type")=="route" then
		local ref = relation:Find("ref")

		if ref~="" then
			-- accept all routes with a ref number
			relation:Accept()
		end
	end
end

However, the debug string MULTIPLE RELATIONS is never printed.

[systemed]

ef4b6e6 should fix this.

[mytracks]

Many thanks for the bug fix. This solved by issue.

[systemed]

No problem - thanks for spotting it!