Set map spatial reference | ArcGIS Maps SDK for Qt

View on GitHub

Sample viewer app

Specify a map's spatial reference.

screenshot

Use case

Choosing the correct spatial reference is important for ensuring accurate projection of data points to a map.

How to use the sample

Pan and zoom around the map. Observe how the map is displayed in the World Bonne spatial reference. Pick a different spatial reference and see the map reproject.

How it works

Create a Map object using a spatial reference e.g. Map(SpatialReference.create(54024)).
Create a Basemap object using an ArcGISMapImageLayer object.
Set the base map to the map.
Set the map to a MapView object.
Change the map's spatial reference using setSpatialReference method.

The ArcGIS map image layer will reproject into the spatial reference set to the map (such as World Bonne (WKID: 54024)), and not the map service's default spatial reference.

Relevant API

ArcGISMapImageLayer
Basemap
Map
MapView
SpatialReference

About the data

This sample uses a World Cities Population map service that displays world cities symbolized based on population.

Additional information

Operational layers will automatically project to this spatial reference when possible. There are 3 kinds of layer reprojection behaviors:

Reprojected on device (on-the-fly reprojection), such as a FeatureLayer created from a mobile geodatabase
Reprojected from the service, such as an ArcGISMapImageLayer
Not able to reproject, such as an ArcGISTiledLayer with defined spatial reference in its tile cache. These layer might be able to reproject in a future update

For more information, check out the API reference doc for setSpatialReference method.

Sample Code

SetMapSpatialReference.cpp

SetMapSpatialReference.h

SetMapSpatialReference.qml

Use dark colors for code blocksCopy
// [WriteFile Name=SetMapSpatialReference, Category=Maps]
// [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 "SetMapSpatialReference.h"

// ArcGIS Maps SDK headers
#include "ArcGISMapImageLayer.h"
#include "Basemap.h"
#include "Map.h"
#include "MapQuickView.h"
#include "MapViewTypes.h"
#include "SpatialReference.h"

// Qt headers
#include <QUrl>

using namespace Esri::ArcGISRuntime;

SetMapSpatialReference::SetMapSpatialReference(QQuickItem* parent) :
  QQuickItem(parent)
{
}

SetMapSpatialReference::~SetMapSpatialReference() = default;

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

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

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

  // Create a new map with the spatial reference
  m_map = new Map(SpatialReference(54024), this);

  // create the URL pointing to the map image layer
  QUrl imageLayerUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/SampleWorldCities/MapServer");

  // construct the ArcGISMapImageLayer using the URL
  m_imageLayer = new ArcGISMapImageLayer(imageLayerUrl, this);

  // create a Basemap and pass in the ArcGISMapImageLayer
  m_basemap = new Basemap(m_imageLayer, this);

  // set the ArcGISMapImageLayer as basemap
  m_map->setBasemap(m_basemap);
  // set map on the map view
  m_mapView->setMap(m_map);
}

QStringList SetMapSpatialReference::spatialReferenceNames() const
{
  QStringList names;
  for (const auto& option : m_srOptions)
  {
    names << option.first;
  }
  return names;
}

void SetMapSpatialReference::setSpatialReference(int index)
{
  if (index < 0 || index >= m_srOptions.size())
  {
    return;
  }
  m_map->setSpatialReference(SpatialReference(m_srOptions[index].second));
}