How do you define rail network branch geocodes

Question

As per the attached document I'm trying to define a rail network by providing geocodes for each rail stop, how would I define a 'stop' as a junction for a branch in the network without having to define each branch option multiple times. For example, if I need to travel from Brisbane to Longreach in one trip and in the next trip Brisbane - Mackay, I don't want to have to define each stop from Brisbane - Rockhamptom for each of these branches. I want Google to pickup in the definition of my geocodes that Rockhampton is the stop which 'forks' into one or more branches, it will then continue to display the polylines of the branch which is closest to the destination.

In summary, in the example I've defined my destination station may be on one of two lines, I don't want to have to define the geocodes for those lines separately especially when they share more than half of the same geocodes up to a certain point, how is this best achieved?

Thanks in advance.

Answer 1

I'm making a couple of assumptions here. First, you're only encoding the points using the Google Earth geocoder, and you can do that already. Second, aside from the PDF you've supplied us you have some sort of data that contains all the names of the stations and their links further down the line. Thirdly I'm guessing that you want to be able to start and end at any station, but you're only interested in the end points and where you would have to change trains.

One way of getting this info would be to use the networkX library in Python, which has some very helpful functions, such as Graph.degree_iter and lots of shortest path algorithms. For example:

import networkx as nx
import matplotlib.pyplot as plt

G = nx.Graph()

G.add_edges_from([["Brisbane", "x"],
                  ["x", "y"],
                  ["y", "Rockhampton"],
                  ["Rockhampton", "Longreach"],
                  ["Rockhampton", "Mackay"]])

def get_nodes(start, finish):
    out_n = []
    skipped_n = []
    for n, d in G.degree_iter(p):
        if n in [start, finish] or d != 2:
            out_n.append(n)
        else:
            skipped_n.append(n)

    pos = nx.spring_layout(G)
    nx.draw_networkx_edges(G, pos)
    nx.draw_networkx_nodes(G, pos, out_n)
    nx.draw_networkx_nodes(G, pos, skipped_n, node_size=150, node_color='b')
    plt.show()

    return out_n

print get_nodes("Brisbane", "Mackay")
print get_nodes("x", "Longreach")