diff --git a/core/src/main/java/org/tinfour/common/NearestEdgeResult.java b/core/src/main/java/org/tinfour/common/NearestEdgeResult.java
index 81796b66..30aa0357 100644
--- a/core/src/main/java/org/tinfour/common/NearestEdgeResult.java
+++ b/core/src/main/java/org/tinfour/common/NearestEdgeResult.java
@@ -76,8 +76,8 @@ private void prepareNearestVertex() {
       for (IQuadEdge e : edge.pinwheel()) {
         Vertex v = e.getB();
         if (v != null) {
-          dX = vMin.getX() - x;
-          dY = vMin.getY() - y;
+          dX = v.getX() - x;
+          dY = v.getY() - y;
           double d2 = dX * dX + dY * dY;
           if (d2 < d2Min) {
             d2Min = d2;
diff --git a/core/src/main/java/org/tinfour/interpolation/NaturalNeighborInterpolator.java b/core/src/main/java/org/tinfour/interpolation/NaturalNeighborInterpolator.java
index 3189fe77..90cac50a 100644
--- a/core/src/main/java/org/tinfour/interpolation/NaturalNeighborInterpolator.java
+++ b/core/src/main/java/org/tinfour/interpolation/NaturalNeighborInterpolator.java
@@ -48,7 +48,7 @@
 import org.tinfour.common.Circumcircle;
 import org.tinfour.common.GeometricOperations;
 import org.tinfour.common.IIncrementalTin;
-import org.tinfour.common.INeighborEdgeLocator;
+import org.tinfour.common.IIncrementalTinNavigator;
 import org.tinfour.common.IQuadEdge;
 import org.tinfour.common.Thresholds;
 import org.tinfour.common.Vertex;
@@ -70,7 +70,7 @@ public class NaturalNeighborInterpolator implements IInterpolatorOverTin {
 
   final IIncrementalTin tin;
   final GeometricOperations geoOp;
-  INeighborEdgeLocator locator;
+  IIncrementalTinNavigator navigator;
 
   private final VertexValuatorDefault defaultValuator = new VertexValuatorDefault();
 
@@ -109,7 +109,7 @@ public NaturalNeighborInterpolator(IIncrementalTin tin) {
     halfPlaneThreshold = thresholds.getHalfPlaneThreshold();
 
     this.tin = tin;
-    locator = tin.getNeighborEdgeLocator();
+    navigator = tin.getNavigator();
   }
 
   /**
@@ -120,7 +120,7 @@ public NaturalNeighborInterpolator(IIncrementalTin tin) {
    */
   @Override
   public void resetForChangeToTin() {
-    locator.resetForChangeToTin();
+    navigator.resetForChangeToTin();
   }
 
   /**
@@ -379,7 +379,7 @@ public List<IQuadEdge> getBowyerWatsonPolygon(double x, double y) {
 
     ArrayList<IQuadEdge> eList = new ArrayList<>();
 
-    IQuadEdge locatorEdge = locator.getNeigborEdge(x, y);
+    IQuadEdge locatorEdge = navigator.getNeighborEdge(x, y);
     if (locatorEdge == null) {
       // this would happen only if the TIN were not bootstrapped
       return eList;
diff --git a/core/src/main/java/org/tinfour/interpolation/TriangularFacetInterpolator.java b/core/src/main/java/org/tinfour/interpolation/TriangularFacetInterpolator.java
index df827fe5..779e1a38 100644
--- a/core/src/main/java/org/tinfour/interpolation/TriangularFacetInterpolator.java
+++ b/core/src/main/java/org/tinfour/interpolation/TriangularFacetInterpolator.java
@@ -31,7 +31,7 @@
 package org.tinfour.interpolation;
 
 import org.tinfour.common.IIncrementalTin;
-import org.tinfour.common.INeighborEdgeLocator;
+import org.tinfour.common.IIncrementalTinNavigator;
 import org.tinfour.common.IQuadEdge;
 import org.tinfour.common.Thresholds;
 import org.tinfour.common.Vertex;
@@ -48,7 +48,7 @@ public class TriangularFacetInterpolator implements IInterpolatorOverTin {
     final private double precisionThreshold;
 
     final IIncrementalTin tin;
-    final INeighborEdgeLocator locator;
+    final IIncrementalTinNavigator navigator;
 
     private final VertexValuatorDefault defaultValuator = new VertexValuatorDefault();
 
@@ -83,7 +83,7 @@ public TriangularFacetInterpolator(IIncrementalTin tin) {
         precisionThreshold = thresholds.getPrecisionThreshold();
 
         this.tin = tin;
-        locator = tin.getNeighborEdgeLocator();
+        navigator = tin.getNavigator();
     }
 
     /**
@@ -94,7 +94,7 @@ public TriangularFacetInterpolator(IIncrementalTin tin) {
      */
     @Override
     public void resetForChangeToTin() {
-        locator.resetForChangeToTin();
+        navigator.resetForChangeToTin();
     }
 
     /**
@@ -125,7 +125,7 @@ public double interpolate(double x, double y, IVertexValuator valuator) {
             vq = defaultValuator;
         }
 
-        IQuadEdge e= locator.getNeigborEdge(x, y);
+        IQuadEdge e= navigator.getNeighborEdge(x, y);
 
         if (e == null) {
           // this should happen only when TIN is not bootstrapped
diff --git a/core/src/main/java/org/tinfour/utils/VertexColorizerKempe6.java b/core/src/main/java/org/tinfour/utils/VertexColorizerKempe6.java
index 1663997f..0f61b597 100644
--- a/core/src/main/java/org/tinfour/utils/VertexColorizerKempe6.java
+++ b/core/src/main/java/org/tinfour/utils/VertexColorizerKempe6.java
@@ -35,7 +35,7 @@
 import java.util.Arrays;
 import java.util.List;
 import org.tinfour.common.IIncrementalTin;
-import org.tinfour.common.INeighborEdgeLocator;
+import org.tinfour.common.IIncrementalTinNavigator;
 import org.tinfour.common.IQuadEdge;
 import org.tinfour.common.Vertex;
 
@@ -99,7 +99,7 @@ public void assignColorsToVertices(IIncrementalTin tin) {
     // The minimum number of connections is two.  For a sufficiently large
     // population, the average number of connections is 6.
     ArrayDeque<Vertex> stack = new ArrayDeque<>();
-    INeighborEdgeLocator locator = tin.getNeighborEdgeLocator();
+    IIncrementalTinNavigator navigator = tin.getNavigator();
     while (!vertexList.isEmpty()) {
       Vertex vRemove = null;
       for (Vertex v : vertexList) {
@@ -110,7 +110,7 @@ public void assignColorsToVertices(IIncrementalTin tin) {
       }
       vertexList.remove(vRemove);
       stack.push(vRemove);
-      IQuadEdge eRemove = locateEdge(locator, vRemove);
+      IQuadEdge eRemove = locateEdge(navigator, vRemove);
       if(eRemove==null){
         throw new IllegalStateException("Internal error, unable to locate edge");
       }
@@ -130,7 +130,7 @@ public void assignColorsToVertices(IIncrementalTin tin) {
     int iStart = 0;
     while (!stack.isEmpty()) {
       Vertex v = stack.pop();
-      IQuadEdge e = locateEdge(locator, v);
+      IQuadEdge e = locateEdge(navigator, v);
       Arrays.fill(flag, true);
       for (IQuadEdge p : e.pinwheel()) {
         Vertex B = p.getB();
@@ -254,11 +254,11 @@ private void setDegree(IQuadEdge e, boolean[] visited, List<Vertex> vertexList)
 
   /**
    * Locate an edge which begins with the specified vertex.
-   * @param locator the edge locator associated with the tin
+   * @param navigator the edge locator associated with the tin
    * @param v a valid vertex
    * @return  a valid edge
    */
-  private IQuadEdge locateEdge(INeighborEdgeLocator locator, Vertex v) {
+  private IQuadEdge locateEdge(IIncrementalTinNavigator navigator, Vertex v) {
     // The Tinfour edge locator identifies an edge belonging to a
     // Triangle in which vertex V lies.  The locator is a general-purpose
     // utility that does not assume that the input coordinates necessarily
@@ -266,7 +266,7 @@ private IQuadEdge locateEdge(INeighborEdgeLocator locator, Vertex v) {
     // will include the input vertex.  Since the colorization logic
     // requires a vertex that begins with input vertex v, a bit more
     // work is required to select the correct edge.
-    IQuadEdge e = locator.getNeigborEdge(v.getX(), v.getY());
+    IQuadEdge e = navigator.getNeighborEdge(v.getX(), v.getY());
     if(e == null){
       // won't happen except when the TIN is not bootstraped
       return null;
diff --git a/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvComposite.java b/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvComposite.java
index bd1b6e4a..7140d458 100644
--- a/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvComposite.java
+++ b/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvComposite.java
@@ -51,9 +51,9 @@
 import org.apache.commons.math3.linear.SingularMatrixException;
 import org.tinfour.common.IConstraint;
 import org.tinfour.common.IIncrementalTin;
-import org.tinfour.common.INeighborEdgeLocator;
+import org.tinfour.common.IIncrementalTinNavigator;
 import org.tinfour.common.IQuadEdge;
-import org.tinfour.common.NeighborEdgeVertex;
+import org.tinfour.common.NearestEdgeResult;
 import org.tinfour.common.PolygonConstraint;
 import org.tinfour.common.Vertex;
 import org.tinfour.gwr.BandwidthSelectionMethod;
@@ -110,7 +110,7 @@ public class MvComposite {
   private List<IConstraint> constraintsForRender;
 
   GwrTinInterpolator interpolator;
-  INeighborEdgeLocator edgeLocator;
+  IIncrementalTinNavigator navigator;
 
   double vx0, vy0, vx1, vy1;
 
@@ -210,7 +210,7 @@ public MvComposite(
       interpolatingTin = model.getReferenceTin();
       reductionForInterpolatingTin = model.getReferenceReductionFactor();
       interpolator = new GwrTinInterpolator(interpolatingTin);
-      edgeLocator = interpolatingTin.getNeighborEdgeLocator();
+      navigator = interpolatingTin.getNavigator();
       applyRangeOfVisibleSamples(model.getVertexList());
     }
 
@@ -250,7 +250,7 @@ public MvComposite(
         this.interpolator = mvComposite.interpolator;
         this.timeForBuildRaster0 = mvComposite.timeForBuildRaster0;
         this.timeForBuildRaster1 = mvComposite.timeForBuildRaster1;
-        this.edgeLocator = mvComposite.edgeLocator;
+        this.navigator = mvComposite.navigator;
         this.constraintsForRender = mvComposite.constraintsForRender;
       }
     }
@@ -262,7 +262,7 @@ public MvComposite(
       interpolatingTin = mvComposite.interpolatingTin;
       reductionForInterpolatingTin = mvComposite.reductionForInterpolatingTin;
       interpolator = new GwrTinInterpolator(interpolatingTin);
-      edgeLocator = interpolatingTin.getNeighborEdgeLocator();
+      navigator = interpolatingTin.getNavigator();
       zVisMin = mvComposite.zVisMin;
       zVisMax = mvComposite.zVisMax;
     }
@@ -289,9 +289,9 @@ public MvComposite(
 
     if (model.isLoaded()) {
       IIncrementalTin ref = model.getReferenceTin();
-      ref.getNeighborEdgeLocator();
+      ref.getNavigator();
       interpolator = new GwrTinInterpolator(ref);
-      edgeLocator = ref.getNeighborEdgeLocator();
+      navigator = ref.getNavigator();
     }
   }
 
@@ -442,7 +442,7 @@ void submitCandidateTinForInterpolation(IIncrementalTin tin, double reductionFac
         interpolatingTin = tin;
         reductionForInterpolatingTin = reductionFactor;
         interpolator = new GwrTinInterpolator(interpolatingTin);
-        edgeLocator = interpolatingTin.getNeighborEdgeLocator();
+        navigator = interpolatingTin.getNavigator();
       }
     }
   }
@@ -924,10 +924,10 @@ public MvQueryResult performQuery(double x, double y) {
         units = "units";
         break;
     }
-    NeighborEdgeVertex nev = edgeLocator.getEdgeWithNearestVertex(mx, my);
-    boolean queryIsOutside = !nev.isInterior();
-    Vertex vNear = nev.getNearestVertex();
-    double dNear = nev.getDistance();
+    NearestEdgeResult result = navigator.getNearestEdge(mx, my);   
+    boolean queryIsOutside = !result.isInterior();
+    Vertex vNear = result.getNearestVertex();
+    double dNear = result.getDistanceToNearestVertex();
 
     // the following is a debugging aid when trying to deal with vertex
     // insertion versus TIN extension.
diff --git a/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvTaskBuildTinAndRender.java b/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvTaskBuildTinAndRender.java
index 062e2609..aa078515 100644
--- a/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvTaskBuildTinAndRender.java
+++ b/demo/src/main/java/org/tinfour/demo/viewer/backplane/MvTaskBuildTinAndRender.java
@@ -37,10 +37,9 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import org.tinfour.common.IConstraint;
 import org.tinfour.common.IIncrementalTin;
+import org.tinfour.common.IIncrementalTinNavigator;
 import org.tinfour.common.IMonitorWithCancellation;
-import org.tinfour.common.INeighborEdgeLocator;
 import org.tinfour.common.IPolyline;
-import org.tinfour.common.NeighborEdgeVertex;
 import org.tinfour.common.PolygonConstraint;
 import org.tinfour.common.Vertex;
 import org.tinfour.utils.PolylineThinner;
@@ -399,10 +398,8 @@ void launchRasterProcessing(double nominalPointSpacing, IIncrementalTin wirefram
 
   private Vertex getNearbyVertex(double x, double y) {
     IIncrementalTin referenceTin = model.getReferenceTin();
-    referenceTin.getNeighborEdgeLocator();
-    INeighborEdgeLocator locator = referenceTin.getNeighborEdgeLocator();
-    NeighborEdgeVertex nev = locator.getEdgeWithNearestVertex(x, y);
-    return nev.getNearestVertex();
+    IIncrementalTinNavigator navigator = referenceTin.getNavigator();
+    return navigator.getNearestVertex(x, y);
   }
 
   /**
diff --git a/svm/src/main/java/org/tinfour/svm/SvmContourGraph.java b/svm/src/main/java/org/tinfour/svm/SvmContourGraph.java
index 28f63b95..1a813a98 100644
--- a/svm/src/main/java/org/tinfour/svm/SvmContourGraph.java
+++ b/svm/src/main/java/org/tinfour/svm/SvmContourGraph.java
@@ -49,7 +49,7 @@
 import javax.imageio.ImageIO;
 import org.tinfour.common.IConstraint;
 import org.tinfour.common.IIncrementalTin;
-import org.tinfour.common.INeighborEdgeLocator;
+import org.tinfour.common.IIncrementalTinNavigator;
 import org.tinfour.common.IQuadEdge;
 import org.tinfour.common.PolygonConstraint;
 import org.tinfour.common.Vertex;
@@ -203,7 +203,7 @@ static void write(
     // it is necessary to force outside values to be at least the
     // shoreline reference elevation.
     ps.println("\nChecking for vertices lying outside of constraints");
-    INeighborEdgeLocator locator = tin.getNeighborEdgeLocator();
+    IIncrementalTinNavigator navigator = tin.getNavigator();
 
     long time0 = System.currentTimeMillis();
     int nOutsiders = 0;
@@ -213,7 +213,7 @@ static void write(
       int index = v.getIndex();
       double x = v.getX();
       double y = v.getY();
-      IQuadEdge test = locator.getNeigborEdge(x, y);
+      IQuadEdge test = navigator.getNeighborEdge(x, y);
       IConstraint con = tin.getRegionConstraint(test);
       if (con == null || !water[con.getConstraintIndex()]) {
         nOutsiders++;
diff --git a/svm/src/main/java/org/tinfour/svm/SvmRaster.java b/svm/src/main/java/org/tinfour/svm/SvmRaster.java
index 60d37c40..e47c0f58 100644
--- a/svm/src/main/java/org/tinfour/svm/SvmRaster.java
+++ b/svm/src/main/java/org/tinfour/svm/SvmRaster.java
@@ -34,7 +34,7 @@
 import java.io.IOException;
 import java.io.PrintStream;
 import org.tinfour.common.IIncrementalTin;
-import org.tinfour.common.INeighborEdgeLocator;
+import org.tinfour.common.IIncrementalTinNavigator;
 import org.tinfour.common.IQuadEdge;
 import org.tinfour.interpolation.NaturalNeighborInterpolator;
 import org.tinfour.svm.properties.SvmProperties;
@@ -112,7 +112,7 @@ void buildAndWriteRaster(
     long reportBlockSize = nRows / 10;
     long priorReportBlock = 0;
     int nCovered = 0;
-    INeighborEdgeLocator locator = tin.getNeighborEdgeLocator();
+    IIncrementalTinNavigator navigator = tin.getNavigator();
     NaturalNeighborInterpolator nni = new NaturalNeighborInterpolator(tin);
     long time0 = System.nanoTime();
     for (long i = iMin; i < iMax; i++) {
@@ -121,7 +121,7 @@ void buildAndWriteRaster(
         int jCol = (int) (j - jMin);
         double x = j * s;
         double y = i * s;
-        IQuadEdge edge = locator.getNeigborEdge(x, y);
+        IQuadEdge edge = navigator.getNeighborEdge(x, y);
         double z = -1;
         if (testWater(edge, water)) {
           z = nni.interpolate(x, y, null);