how to build a routeable network for pgRouting with srid 3785

Question

I'm following the pgrouting-workshop http://workshop.pgrouting.org/chapters/topology.html and It works, but in my project I'm working with the mercator projection(srid 3785) and there is not a routed network like the Open Street Map to work in, so I need to build my own.. so for testing purposes with the help of google maps and Proj4js I build a simple graph like this

point1 = "POINT (-7363703.972517611 -1966750.4952863816)"
point2 = "POINT (-7363530.794875402 -1966719.4427436402)"
point3 = "POINT (-7363414.945004408 -1966694.3618437336)"
point4 = "POINT (-7363365.977533163 -1966681.2242294976)"
point5 = "POINT (-7363419.722318676 -1966658.5319867264)"
point6 = "POINT (-7363344.479618957 -1966793.4911147922)"
// it's in lon / lat format

Then the geom column in ways table
way_red = "MULTILINESTRING((point1, point2, point3, point4))"
way_green = "MULTILINESTRING((point3, point5))"
way_blue = "MULTILINESTRING((point4, point6))"

Questions:

1. Is it correct the format I builded the ways ??
2. Exist a correct or pre-established format to construct a routeable network?
3. the workshop uses "MULTILINESTRING", is it ok if I use just "LINESTRING"??

Thanks in advance, and sorry for my english.

Answer 1

1) Is it correct the format I builded the ways ??

Not quite. The red way has to be split at point 3. Ways have to be split at each intersection if turning should be possible there.

Also the point coordinates you specified cannot be valid latitudes/longitudes.

2) Exist a correct or pre-established format to construct a routeable network?

You generally need a source node id (or "from_node") and a target node id (or "to_node") plus some edge weight (can be length/distance or travel time or energy cost). Some algorithms will also use the actual geometry (MULTI/LINESTRING) but basic shortest path doesn't.

3) the workshop uses "MULTILINESTRING", is it ok if I use just "LINESTRING"??

That's fine. You shouldn't encounter multilinestrings in routing graphs anyway.

Answer 2

1. Is it correct the format I builded the ways ?
2. Exist a correct or pre-established format to construct a routeable network?

If your network data is not OSM data and it doesn't contain information about source and target of each road segment, then you can use the assign_vertex_id function to prepare your data for routing. See: http://workshop.pgrouting.org/chapters/topology.html#calculate-topology

If your data is in a different projection than you need, you can use ST_transform to re-project into the SRID you need: http://postgis.net/docs/ST_Transform.html

1. the workshop uses "MULTILINESTRING", is it ok if I use just "LINESTRING"?

Yes.