Geodesic operations

View inQMLC++
View on GitHub
Sample viewer app

Calculate a geodesic path between two points and measure its distance.

screenshot

Use case

A geodesic distance provides an accurate, real-world distance between two points. Visualizing flight paths between cities is a common example of a geodesic operation since the flight path between two airports takes into account the curvature of the earth, rather than following the planar path between those points, which appears as a straight line on a projected map.

How to use the sample

Click anywhere on the map. A line graphic will display the geodesic line between the two points. In addition, text that indicates the geodesic distance between the two points will be updated. Click elsewhere and a new line will be created.

How it works

  1. Create a Point in New York City and display it as a Graphic.
  2. Obtain a new point when a click occurs on the MapView and add this point as a graphic.
  3. Create a Polyline from the two points.
  4. Execute GeometryEngine::densifyGeodetic by passing in the created polyine then create a graphic from the returned Geometry.
  5. Execute GeometryEngine::lengthGeodetic by passing in the two points and display the returned length on the screen.

Relevant API

  • GeometryEngine::densifyGeodetic
  • GeometryEngine::lengthGeodetic

About the data

The Imagery basemap provides the global context for the displayed geodesic line.

Tags

densify, distance, geodesic, geodetic

Sample Code

GeodesicOperations.cppGeodesicOperations.cppGeodesicOperations.hGeodesicOperations.qml
Use dark colors for code blocksCopy
                                                                                                                              
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
// [WriteFile Name=GeodesicOperations, Category=Geometry]
// [Legal]
// Copyright 2018 Esri.

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0

// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// [Legal]

#ifdef PCH_BUILD
#include "pch.hpp"
#endif // PCH_BUILD

#include "GeodesicOperations.h"

#include "Map.h"
#include "MapQuickView.h"
#include "GraphicsOverlay.h"
#include "Graphic.h"
#include "SimpleMarkerSymbol.h"
#include "SimpleLineSymbol.h"
#include "GeometryEngine.h"
#include "SpatialReference.h"
#include "PolylineBuilder.h"
#include "Point.h"

using namespace Esri::ArcGISRuntime;

GeodesicOperations::GeodesicOperations(QQuickItem* parent /* = nullptr */):
  QQuickItem(parent)
{
}

void GeodesicOperations::init()
{
  // Register the map view for QML
  qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
  qmlRegisterType<GeodesicOperations>("Esri.Samples", 1, 0, "GeodesicOperationsSample");
}

void GeodesicOperations::componentComplete()
{
  QQuickItem::componentComplete();

  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");

  // Create a map using the imagery basemap
  m_map = new Map(BasemapStyle::ArcGISImageryStandard, this);

  // Set map to map view
  m_mapView->setMap(m_map);

  // Create a GraphicsOverlay
  GraphicsOverlay* graphicsOverlay = new GraphicsOverlay(this);
  m_mapView->graphicsOverlays()->append(graphicsOverlay);

  // Create Graphic Symbols
  SimpleMarkerSymbol* markerSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("blue"), 10.0f /*size*/, this);
  SimpleLineSymbol* pathSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle::Dash, QColor("blue"), 5.0f /*width*/, this);

  // Create NYC graphic
  const Point nycPoint(-73.7781, 40.6413, SpatialReference(4326));
  m_nycGraphic = new Graphic(nycPoint, markerSymbol, this);
  graphicsOverlay->graphics()->append(m_nycGraphic);

  // Create destination graphic
  m_destinationGraphic = new Graphic(this);
  m_destinationGraphic->setSymbol(markerSymbol);
  graphicsOverlay->graphics()->append(m_destinationGraphic);

  // Create path graphic
  m_pathGraphic = new Graphic(this);
  m_pathGraphic->setSymbol(pathSymbol);
  graphicsOverlay->graphics()->append(m_pathGraphic);

  // connect to mouse clicked signal
  connect(m_mapView, &MapQuickView::mouseClicked, this, [this, nycPoint](QMouseEvent& mouseEvent)
  {
    // re-project the point to match the NYC graphic
    const Point clickedPoint = m_mapView->screenToLocation(mouseEvent.x(), mouseEvent.y());
    const Point destination = GeometryEngine::project(clickedPoint, m_nycGraphic->geometry().spatialReference());

    // update the destination graphic
    m_destinationGraphic->setGeometry(destination);

    // create line with start/end points
    const QList<Point> points = {nycPoint, destination};
    const Polyline polyline = pointsToPolyline(points);

    // densify the path as a geodesic curve and show it with the path graphic
    constexpr double maxSegmentLength = 1.0;
    const LinearUnit unitOfMeasurement(LinearUnitId::Kilometers);
    constexpr GeodeticCurveType curveType = GeodeticCurveType::Geodesic;
    const Geometry pathGeometry = GeometryEngine::densifyGeodetic(polyline, maxSegmentLength, unitOfMeasurement, curveType);

    // update the graphic
    m_pathGraphic->setGeometry(pathGeometry);

    // calculate the path's geodetic length
    m_distanceText = QString::number(GeometryEngine::lengthGeodetic(pathGeometry, unitOfMeasurement, curveType), 'f', 2);
    emit distanceTextChanged();
  });
}

// helper function to create a new Polyline from a list of points
Polyline GeodesicOperations::pointsToPolyline(const QList<Point>& points)
{
  PolylineBuilder polylineBuilder(SpatialReference(4326));
  for (const Point& point : points)
    polylineBuilder.addPoint(point);

  return polylineBuilder.toPolyline();
}

QString GeodesicOperations::distanceText() const
{
  return m_distanceText;
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.