Viewshed (Geoprocessing)

View on GitHubSample viewer app

Calculate a viewshed using a geoprocessing service, in this case showing which parts of a landscape are visible from points on mountainous terrain.

screenshot

Use case

A viewshed is used to highlight what is visible from a given point. A viewshed could be created to show what a hiker might be able to see from a given point at the top of a mountain. Equally, a viewshed could also be created from a point representing the maximum height of a proposed wind turbine to see from what areas the turbine would be visible.

How to use the sample

Click the map to see all areas visible from that point within a 15km radius. Clicking on an elevated area will highlight a larger part of the surrounding landscape. It may take a few seconds for the task to run and send back the results.

How it works

  1. Create a GeoprocessingTask object with the URL set to a geoprocessing service endpoint.
  2. Create a FeatureCollectionTable object and add a new Feature object whose geometry is the viewshed's observer Point.
  3. Make a GeoprocessingParameters object passing in the observer point.
  4. Use the geoprocessing task to create a GeoprocessingJob object with the parameters.
  5. Start the job and wait for it to complete and return a GeoprocessingResult object.
  6. Get the resulting GeoprocessingFeatures object.
  7. Iterate through the viewshed features to use their geometry or display the geometry in a new Graphic object.

Relevant API

  • FeatureCollectionTable
  • GeoprocessingFeatures
  • GeoprocessingJob
  • GeoprocessingParameters
  • GeoprocessingResult
  • GeoprocessingTask

Tags

geoprocessing, heat map, heatmap, viewshed

Sample Code

AnalyzeViewshed.cppAnalyzeViewshed.cppAnalyzeViewshed.hAnalyzeViewshed.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
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
// [WriteFile Name=AnalyzeViewshed, Category=Analysis]
// [Legal]
// Copyright 2016 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

// sample headers
#include "AnalyzeViewshed.h"

// ArcGIS Maps SDK headers
#include "Error.h"
#include "Feature.h"
#include "FeatureCollectionTable.h"
#include "FeatureIterator.h"
#include "Field.h"
#include "GeoprocessingFeatures.h"
#include "GeoprocessingJob.h"
#include "GeoprocessingParameter.h"
#include "GeoprocessingParameters.h"
#include "GeoprocessingResult.h"
#include "GeoprocessingTask.h"
#include "GeoprocessingTypes.h"
#include "Graphic.h"
#include "GraphicListModel.h"
#include "GraphicsOverlay.h"
#include "GraphicsOverlayListModel.h"
#include "Map.h"
#include "MapQuickView.h"
#include "MapTypes.h"
#include "MapViewTypes.h"
#include "Point.h"
#include "SimpleFillSymbol.h"
#include "SimpleMarkerSymbol.h"
#include "SimpleRenderer.h"
#include "SpatialReference.h"
#include "SymbolTypes.h"
#include "TaskTypes.h"
#include "Viewpoint.h"

// Qt headers
#include <QFuture>
#include <QMouseEvent>
#include <QUuid>

using namespace Esri::ArcGISRuntime;

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

AnalyzeViewshed::~AnalyzeViewshed() = default;

void AnalyzeViewshed::init()
{
  qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
  qmlRegisterType<AnalyzeViewshed>("Esri.Samples", 1, 0, "AnalyzeViewshedSample");
}

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

  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");
  m_mapView->setWrapAroundMode(WrapAroundMode::Disabled);

  // Create a map using the topographic basemap
  m_map = new Map(BasemapStyle::ArcGISTopographic, this);
  m_map->setInitialViewpoint(Viewpoint(Point(6.84905317262762, 45.3790902612337, SpatialReference(4326)), 100000));

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

  // Create the GeoprocessingTask
  m_viewshedTask = new GeoprocessingTask(QUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/Elevation/ESRI_Elevation_World/GPServer/Viewshed"), this);

  // Create the Graphics Overlays
  createOverlays();

  // Connect signals
  connectSignals();
}

void AnalyzeViewshed::createOverlays()
{
  // Create the graphics overlays for the input and output
  m_inputOverlay = new GraphicsOverlay(this);
  m_inputGraphic = new Graphic(this);
  m_inputOverlay->graphics()->append(m_inputGraphic);
  SimpleMarkerSymbol* sms = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("red"), 12.0, this);
  SimpleRenderer* inputRenderer = new SimpleRenderer(sms, this);
  m_inputOverlay->setRenderer(inputRenderer);
  m_mapView->graphicsOverlays()->append(m_inputOverlay);

  m_resultsOverlay = new GraphicsOverlay(this);
  SimpleFillSymbol* sfs = new SimpleFillSymbol(SimpleFillSymbolStyle::Solid, QColor(226, 119, 40, 100), this);
  SimpleRenderer* outputRenderer = new SimpleRenderer(sfs, this);
  m_resultsOverlay->setRenderer(outputRenderer);
  m_mapView->graphicsOverlays()->append(m_resultsOverlay);
}

void AnalyzeViewshed::connectSignals()
{
  // Set up signal handler for the mouse clicked signal
  connect(m_mapView, &MapQuickView::mouseClicked, this, [this](QMouseEvent& mouse)
  {
    // The geoprocessing task is still executing, don't do anything else (i.e. respond to
    // more user taps) until the processing is complete.
    if (m_viewshedInProgress)
      return;

    // Indicate that the geoprocessing is running
    m_viewshedInProgress = true;

    // Clear previous viewshed geoprocessing task results
    m_resultsOverlay->graphics()->clear();
    if (m_graphicParent)
    {
      delete m_graphicParent;
      m_graphicParent = nullptr;
    }

    // Create a marker graphic where the user clicked on the map and add it to the existing graphics overlay
    Point mapPoint = m_mapView->screenToLocation(mouse.position().x(), mouse.position().y());
    if (m_inputGraphic)
      m_inputGraphic->setGeometry(mapPoint);

    // Setup the geoprocessing task
    calculateViewshed();
  });

  // Connect to the GP Task's errorOccurred signal
  connect(m_viewshedTask, &GeoprocessingTask::errorOccurred, this, [this](const Error& error)
  {
    emit displayErrorDialog("Geoprocessing Task failed", error.message());
  });
}

void AnalyzeViewshed::calculateViewshed()
{
  // Create a new feature collection table based upon point geometries using the current map view spatial reference
  FeatureCollectionTable* inputFeatures = new FeatureCollectionTable(QList<Field>(),
                                                                     GeometryType::Point,
                                                                     SpatialReference::webMercator(),
                                                                     this);

  // Create a new feature from the feature collection table. It will not have a coordinate location (x,y) yet
  Feature* inputFeature = inputFeatures->createFeature(this);

  // Assign a physical location to the new point feature based upon where the user clicked on the map view
  inputFeature->setGeometry(m_inputOverlay->graphics()->at(0)->geometry());

  // Add the new feature with (x,y) location to the feature collection table
  inputFeatures->addFeatureAsync(inputFeature).then(this, [this, inputFeatures]()
  {
    onAddFeatureCompleted_(inputFeatures);
  });
}

void AnalyzeViewshed::onAddFeatureCompleted_(FeatureCollectionTable* inputFeatures)
{
  // Create the parameters that are passed to the used geoprocessing task
  GeoprocessingParameters viewshedParameters = GeoprocessingParameters(GeoprocessingExecutionType::SynchronousExecute);

  // Request the output features to use the same SpatialReference as the map view
  viewshedParameters.setOutputSpatialReference(SpatialReference::webMercator());

  // Add an input location to the geoprocessing parameters
  QMap<QString, GeoprocessingParameter*> inputs;
  inputs["Input_Observation_Point"] = new GeoprocessingFeatures(inputFeatures, this);
  viewshedParameters.setInputs(inputs);

  // Create the job that handles the communication between the application and the geoprocessing task
  GeoprocessingJob* viewshedJob = m_viewshedTask->createJob(viewshedParameters);

  // Create signal handler for the job
  connect(viewshedJob, &GeoprocessingJob::statusChanged, this, [this, viewshedJob](JobStatus jobStatus)
  {
    switch (jobStatus)
    {
    case JobStatus::Failed:
      emit displayErrorDialog("Geoprocessing Task failed", !viewshedJob->error().isEmpty() ? viewshedJob->error().message() : "Unknown error.");
      m_viewshedInProgress = false;
      m_jobStatus = "Job failed";
      break;
    case JobStatus::Started:
      m_viewshedInProgress = true;
      m_jobStatus = "Job in progress...";
      break;
    case JobStatus::Paused:
      m_viewshedInProgress = false;
      m_jobStatus = "Job paused...";
      break;
    case JobStatus::Succeeded:
      m_viewshedInProgress = false;
      m_jobStatus = "Job succeeded";
      // handle the results
      processResults(viewshedJob->result());
      break;
    default:
      break;
    }

    // emit signals
    emit viewshedInProgressChanged();
    emit statusChanged();
  });

  // start the job
  viewshedJob->start();
}

void AnalyzeViewshed::processResults(GeoprocessingResult *results)
{
  // Get the results from the outputs as GeoprocessingFeatures
  const auto outputs = results->outputs();
  GeoprocessingFeatures* viewshedResultFeatures = static_cast<GeoprocessingFeatures*>(outputs["Viewshed_Result"]);

  // Create the parent for the graphic
  if (!m_graphicParent)
    m_graphicParent = new QObject(this);

  // Add all the features from the result feature set as a graphics to the map
  FeatureIterator features = viewshedResultFeatures->features()->iterator();
  while (features.hasNext())
  {
    Feature* feat = features.next(this);
    Graphic* graphic = new Graphic(feat->geometry(), m_graphicParent);
    m_resultsOverlay->graphics()->append(graphic);
  }
}

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