Get all streets within a certain radius with osm2po

Question

I'm trying to get all street segments out of osm2po graph, given a geo point and a certain radius. Right now I just do a breadth first search out of the street that's closest to my point, but is there a better way?

class AreaIterator implements Iterator<DirectedStreet> {
    private Set<Integer> visited = new HashSet<>();
    private List<Integer> queue = new LinkedList<>();
    private final Graph graph;
    private final GeoPoint center;
    private final float radius;
    private final boolean twoSided;

    public AreaIterator(Graph graph, GeoPoint center, float radius) {
        this.graph = graph;
        this.center = center;
        this.radius = radius;
        List<Integer> edges = getEdgesForPoint((float) center.lat(), (float) center.lon(), graph);
        queue.addAll(edges);
    }

    private int step() {
        int edgeIdx = 0;
        if (!queue.isEmpty()) {
            edgeIdx = queue.remove(0);
            DirectedStreet street = getDirectedStreetFromEdgeIdx(graph, edgeIdx);
            if (!visited.contains(edgeIdx)) {
                visited.add(edgeIdx);

                if (street.getGeom().distance(center.getGeom()) <= radius)  {
                    int sourceId = graph.getEdgeSourceIds()[edgeIdx];
                    int targetId = graph.getEdgeTargetIds()[edgeIdx];
                    int [] next = graph.findOutgoingEdges(targetId);
                    int [] in1 = graph.findIncomingEdges(targetId);
                    int [] in2 = graph.findIncomingEdges(sourceId);

                    queueAll(next);
                    queueAll(in1);
                    queueAll(in2);
                }
            }
        }

        return edgeIdx;
    }

    private void queueAll(int[] in) {
        for (int edgeIdx : in) {
            queue.add(edgeIdx);
        }
    }

    @Override
    public boolean hasNext() {
        return !queue.isEmpty();
    }

    @Override
    public DirectedStreet next() {
        return getDirectedStreetFromEdgeIdx(graph, step());
    }
}

Answer 1

No, there is no direct method for it.

If you only need the reachability, then just calculate the route and limit the search radius by using the maxCost-Parameter:

int[] findPath(Graph graph, int sourceId, int targetId,
        float maxCost, Properties params);

If you are going to draw sth. (osm2po is no drawing basis though) - regardless whether streets are part of the connected network or not, you'll have to dig deeper into the API.

Use this constructor:

public Graph(final File graphFile, final Log log, final int supports,
        final boolean async, final byte... excludedExtensionClazzes)

• Set the third parameter to at least SUPPORT_RASTER_EDGE | SUPPORT_LATLON
• Use getEdgeRasterBag() which returns a geo-grid of streets
• The key is a zone denoted by an Id and the value the edgeIdx
• The size of a cell/zone is 0.01 x 0.01 degrees.

Nevertheless, you'll have to collect the zoneIds before filtering to a circle radius. Therefore you'll need to understand the formula behind this magic Id - it's pretty simple and straight forward:

public static int createZoneId(double lat, double lon) {
    int ilat = ((int)(lat * 100d)) + 9000;
    int ilon = ((int)(lon * 100d)) + 18000;
    return ilat << 16 | ilon;
}