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Parameterize elevation propagation
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The existing logic is modified so that is deterministic and tested.

The new logic interpolates the elevation for each vertex that is within
maxElevationPropagationDistance on the street network using the two
closest vertices with elevation.
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@flaktack
flaktack committed Mar 28, 2022
1 parent 7c3ebf4 commit 9345d6f
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Showing 9 changed files with 633 additions and 339 deletions.
1 change: 1 addition & 0 deletions docs/BuildConfiguration.md
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Expand Up @@ -19,6 +19,7 @@ This table lists all the JSON properties that can be defined in a `build-config.
| `matchBusRoutesToStreets` | Based on GTFS shape data, guess which OSM streets each bus runs on to improve stop linking | boolean | false | |
| `maxAreaNodes` | Visibility calculations for an area will not be done if there are more nodes than this limit | integer | 500 | |
| `maxDataImportIssuesPerFile` | If number of data import issues is larger then specified maximum number of issues the report will be split in multiple files | int | 1,000 | |
| `maxElevationPropagationMeters` | The maximum distance to propagate elevation to vertices which have no elevation. | int | 2,000 | see [Elevation Data](#elevation-data) |
| `maxInterlineDistance` | Maximal distance between stops in meters that will connect consecutive trips that are made with same vehicle | int | 200 | units: meters |
| `maxStopToShapeSnapDistance` | This field is used for mapping route's geometry shapes. It determines max distance between shape points and their stop sequence. If the mapper can not find any stops within this radius it will default to simple stop-to-stop geometry instead. | double | 150 | units: meters |
| `maxTransferDurationSeconds` | Transfers up to this duration in seconds will be pre-calculated and included in the Graph | double | 1800 | units: seconds |
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1 change: 1 addition & 0 deletions src/main/java/org/opentripplanner/graph_builder/GraphBuilder.java
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Expand Up @@ -204,6 +204,7 @@ public static GraphBuilder create(
config.writeCachedElevations,
config.elevationUnitMultiplier,
config.distanceBetweenElevationSamples,
config.maxElevationPropagationMeters,
config.includeEllipsoidToGeoidDifference,
config.multiThreadElevationCalculations
)
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247 changes: 30 additions & 217 deletions src/main/java/org/opentripplanner/graph_builder/module/ned/ElevationModule.java
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Expand Up @@ -13,9 +13,9 @@
import java.time.Duration;
import java.time.Instant;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.geotools.geometry.DirectPosition2D;
Expand All @@ -27,11 +27,9 @@
import org.opengis.referencing.operation.TransformException;
import org.opentripplanner.common.geometry.GeometryUtils;
import org.opentripplanner.common.geometry.SphericalDistanceLibrary;
import org.opentripplanner.common.pqueue.BinHeap;
import org.opentripplanner.graph_builder.DataImportIssueStore;
import org.opentripplanner.graph_builder.issues.ElevationFlattened;
import org.opentripplanner.graph_builder.issues.ElevationProfileFailure;
import org.opentripplanner.graph_builder.issues.ElevationPropagationLimit;
import org.opentripplanner.graph_builder.issues.Graphwide;
import org.opentripplanner.graph_builder.module.extra_elevation_data.ElevationPoint;
import org.opentripplanner.graph_builder.services.GraphBuilderModule;
Expand Down Expand Up @@ -70,6 +68,7 @@ public class ElevationModule implements GraphBuilderModule {
private final boolean writeCachedElevations;
/* The file of cached elevations */
private final File cachedElevationsFile;
private final double maxElevationPropagationMeters;
/* Whether or not to include geoid difference values in individual elevation calculations */
private final boolean includeEllipsoidToGeoidDifference;
/*
Expand Down Expand Up @@ -125,6 +124,7 @@ public ElevationModule(ElevationGridCoverageFactory factory) {
false,
1,
10,
2000,
true,
false
);
Expand All @@ -137,6 +137,7 @@ public ElevationModule(
boolean writeCachedElevations,
double elevationUnitMultiplier,
double distanceBetweenSamplesM,
double maxElevationPropagationMeters,
boolean includeEllipsoidToGeoidDifference,
boolean multiThreadElevationCalculations
) {
Expand All @@ -145,6 +146,7 @@ public ElevationModule(
this.readCachedElevations = readCachedElevations;
this.writeCachedElevations = writeCachedElevations;
this.elevationUnitMultiplier = elevationUnitMultiplier;
this.maxElevationPropagationMeters = maxElevationPropagationMeters;
this.includeEllipsoidToGeoidDifference = includeEllipsoidToGeoidDifference;
this.multiThreadElevationCalculations = multiThreadElevationCalculations;
this.distanceBetweenSamplesM = distanceBetweenSamplesM;
Expand Down Expand Up @@ -250,13 +252,18 @@ public void buildGraph(
out.writeObject(newCachedElevations);
out.close();
} catch (IOException e) {
LOG.error(e.getMessage());
issueStore.add(new Graphwide("Failed to write cached elevation file!"));
issueStore.add(new Graphwide("Failed to write cached elevation file: " + e.getMessage()));
}
}

@SuppressWarnings("unchecked")
HashMap<Vertex, Double> extraElevation = (HashMap<Vertex, Double>) extra.get(ElevationPoint.class);
assignMissingElevations(graph, edgesWithCalculatedElevations, extraElevation);
Map<Vertex, Double> extraElevation = (Map<Vertex, Double>) extra.get(ElevationPoint.class);
var elevationsForVertices = collectKnownElevationsForVertices(extraElevation, edgesWithCalculatedElevations);

new MissingElevationHandler(
issueStore, elevationsForVertices, maxElevationPropagationMeters
)
.run();

updateElevationMetadata(graph);

Expand All @@ -271,244 +278,50 @@ private void updateElevationMetadata(Graph graph) {
}
}

static class ElevationRepairState {
/* This uses an intuitionist approach to elevation inspection */
public StreetEdge backEdge;

public ElevationRepairState backState;

public Vertex vertex;

public double distance;

public double initialElevation;

public ElevationRepairState(StreetEdge backEdge, ElevationRepairState backState,
Vertex vertex, double distance, double initialElevation) {
this.backEdge = backEdge;
this.backState = backState;
this.vertex = vertex;
this.distance = distance;
this.initialElevation = initialElevation;
}
}

/**
* Assign missing elevations by interpolating from nearby points with known
* elevation; also handle osm ele tags
*/
private void assignMissingElevations(Graph graph, List<StreetEdge> edgesWithElevation, HashMap<Vertex, Double> knownElevations) {

LOG.debug("Assigning missing elevations");

BinHeap<ElevationRepairState> pq = new BinHeap<>();

// elevation for each vertex (known or interpolated)
private Map<Vertex, Double> collectKnownElevationsForVertices(
Map<Vertex, Double> knownElevations,
List<StreetEdge> edgesWithElevation
) {
// knownElevations will be null if there are no ElevationPoints in the data
// for instance, with the Shapefile loader.)
HashMap<Vertex, Double> elevations;
if (knownElevations != null)
elevations = (HashMap<Vertex, Double>) knownElevations.clone();
else
elevations = new HashMap<>();

// If including the EllipsoidToGeoidDifference, subtract these from the known elevations found in OpenStreetMap
// data.
var elevations = knownElevations != null
? new HashMap<>(knownElevations)
: new HashMap<Vertex, Double>();

// If including the EllipsoidToGeoidDifference, subtract these from the known elevations
// found in OpenStreetMap data.
if (includeEllipsoidToGeoidDifference) {
elevations.forEach((vertex, elevation) -> {
try {
elevations.put(
vertex, elevation - getApproximateEllipsoidToGeoidDifference(vertex.getY(), vertex.getX())
vertex, elevation - getApproximateEllipsoidToGeoidDifference(vertex.getY(), vertex.getX())
);
} catch (TransformException e) {
LOG.error(
"Error processing elevation for known elevation at vertex: {} due to error: {}",
vertex,
e
"Error processing elevation for known elevation at vertex: {} due to error: {}",
vertex,
e
);
}
});
}

HashSet<Vertex> closed = new HashSet<>();

// initialize queue with all vertices which already have known elevation
// add all vertices which known elevation
for (StreetEdge e : edgesWithElevation) {
PackedCoordinateSequence profile = e.getElevationProfile();

if (!elevations.containsKey(e.getFromVertex())) {
double firstElevation = profile.getOrdinate(0, 1);
ElevationRepairState state = new ElevationRepairState(
null,
null,
e.getFromVertex(),
0,
firstElevation
);
pq.insert(state, 0);
elevations.put(e.getFromVertex(), firstElevation);
}

if (!elevations.containsKey(e.getToVertex())) {
double lastElevation = profile.getOrdinate(profile.size() - 1, 1);
ElevationRepairState state = new ElevationRepairState(
null,
null,
e.getToVertex(),
0,
lastElevation
);
pq.insert(state, 0);
elevations.put(e.getToVertex(), lastElevation);
}
}

// Grow an SPT outward from vertices with known elevations into regions where the
// elevation is not known. when a branch hits a region with known elevation, follow the
// back pointers through the region of unknown elevation, setting elevations via interpolation.
while (!pq.empty()) {
ElevationRepairState state = pq.extract_min();

if (closed.contains(state.vertex)) continue;
closed.add(state.vertex);

ElevationRepairState curState = state;
Vertex initialVertex = null;
while (curState != null) {
initialVertex = curState.vertex;
curState = curState.backState;
}

double bestDistance = Double.MAX_VALUE;
double bestElevation = 0;
for (Edge e : state.vertex.getOutgoing()) {
if (!(e instanceof StreetEdge)) {
continue;
}
StreetEdge edge = (StreetEdge) e;
Vertex tov = e.getToVertex();
if (tov == initialVertex)
continue;

Double elevation = elevations.get(tov);
if (elevation != null) {
double distance = e.getDistanceMeters();
if (distance < bestDistance) {
bestDistance = distance;
bestElevation = elevation;
}
} else {
// continue
ElevationRepairState newState = new ElevationRepairState(
edge,
state,
tov,
e.getDistanceMeters() + state.distance,
state.initialElevation
);
pq.insert(newState, e.getDistanceMeters() + state.distance);
}
} // end loop over outgoing edges

for (Edge e : state.vertex.getIncoming()) {
if (!(e instanceof StreetEdge)) {
continue;
}
StreetEdge edge = (StreetEdge) e;
Vertex fromv = e.getFromVertex();
if (fromv == initialVertex)
continue;
Double elevation = elevations.get(fromv);
if (elevation != null) {
double distance = e.getDistanceMeters();
if (distance < bestDistance) {
bestDistance = distance;
bestElevation = elevation;
}
} else {
// continue
ElevationRepairState newState = new ElevationRepairState(
edge,
state,
fromv,
e.getDistanceMeters() + state.distance,
state.initialElevation
);
pq.insert(newState, e.getDistanceMeters() + state.distance);
}
} // end loop over incoming edges

//limit elevation propagation to at max 2km; this prevents an infinite loop
//in the case of islands missing elevation (and some other cases)
if (bestDistance == Double.MAX_VALUE && state.distance > 2000) {
issueStore.add(new ElevationPropagationLimit(state.vertex));
bestDistance = state.distance;
bestElevation = state.initialElevation;
}
if (bestDistance != Double.MAX_VALUE) {
// we have found a second vertex with elevation, so we can interpolate the elevation
// for this point
double totalDistance = bestDistance + state.distance;
// trace backwards, setting states as we go
while (true) {
// watch out for division by 0 here, which will propagate NaNs
// all the way out to edge lengths
if (totalDistance == 0)
elevations.put(state.vertex, bestElevation);
else {
double elevation = (bestElevation * state.distance +
state.initialElevation * bestDistance) / totalDistance;
elevations.put(state.vertex, elevation);
}
if (state.backState == null)
break;
bestDistance += state.backEdge.getDistanceMeters();
state = state.backState;
if (elevations.containsKey(state.vertex))
break;
}

}
} // end loop over states

// do actual assignments
for (Vertex v : graph.getVertices()) {
Double fromElevation = elevations.get(v);
for (Edge e : v.getOutgoing()) {
if (e instanceof StreetEdge) {
StreetEdge edge = ((StreetEdge) e);

Double toElevation = elevations.get(edge.getToVertex());

if (fromElevation == null || toElevation == null) {
if (!edge.isElevationFlattened() && !edge.isSlopeOverride()) {
issueStore.add(new ElevationProfileFailure(edge, "Failed to propagate elevation data"));
}
continue;
}

if (edge.getElevationProfile() != null && edge.getElevationProfile().size() > 2) {
continue;
}

Coordinate[] coords = new Coordinate[2];
coords[0] = new Coordinate(0, fromElevation);
coords[1] = new Coordinate(edge.getDistanceMeters(), toElevation);

PackedCoordinateSequence profile = new PackedCoordinateSequence.Double(coords);

try {
StreetElevationExtension.addToEdge(edge, profile, true);

if (edge.isElevationFlattened()) {
issueStore.add(new ElevationFlattened(edge));
}
} catch (Exception ex) {
issueStore.add(new ElevationProfileFailure(edge, ex.getMessage()));
}
}
}
}
return elevations;
}

/**
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