Project a point from one spatial reference to another.
Use case
Being able to project between spatial references is fundamental to a GIS. An example of when you would need to re-project data is if you had data in two different spatial references, but wanted to perform an intersect analysis with the GeometryEngine::intersect function. This function takes two geometries as parameters, and both geometries must be in the same spatial reference. If they are not, you could first use GeometryEngine::project to convert the geometries so they match.
How to use the sample
Click anywhere on the map. A callout will display the clicked location's coordinate in the original (basemap's) spatial reference and in the projected spatial reference.
How it works
- Call the static method,
GeometryEngine::project, passing in the originalGeometryand aSpatialReferenceto which it should be projected.
Relevant API
- GeometryEngine
- Point
- SpatialReference
Additional information
In cases where the the output spatial reference uses a different geographic coordinate system than that of the input spatial reference, see the GeometryEngine.project method that additionally takes in a DatumTransformation parameter.
Tags
coordinate system, coordinates, latitude, longitude, projected, projection, spatial reference, Web Mercator, WGS 84
Sample Code
// [WriteFile Name=ProjectGeometry, 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 // sample headers #include "ProjectGeometry.h" // ArcGIS Maps SDK headers #include "CalloutData.h" #include "Envelope.h" #include "GeometryEngine.h" #include "Graphic.h" #include "GraphicListModel.h" #include "GraphicsOverlay.h" #include "GraphicsOverlayListModel.h" #include "Map.h" #include "MapQuickView.h" #include "MapTypes.h" #include "Point.h" #include "SimpleMarkerSymbol.h" #include "SpatialReference.h" #include "SymbolTypes.h" #include "Viewpoint.h" using namespace Esri::ArcGISRuntime; ProjectGeometry::ProjectGeometry(QQuickItem* parent /* = nullptr */): QQuickItem(parent) { } void ProjectGeometry::init() { // Register the map view for QML qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView"); qmlRegisterType<ProjectGeometry>("Esri.Samples", 1, 0, "ProjectGeometrySample"); qmlRegisterUncreatableType<CalloutData>("Esri.Samples", 1, 0, "CalloutData", "CalloutData is an uncreatable type"); } void ProjectGeometry::componentComplete() { QQuickItem::componentComplete(); // find QML MapView component m_mapView = findChild<MapQuickView*>("mapView"); // connect to mouse clicked signal connect(m_mapView, &MapQuickView::mouseClicked, this, &ProjectGeometry::onMouseClicked); // Create a map using a topographic basemap m_map = new Map(BasemapStyle::ArcGISTopographic, this); // Set initial viewpoint to Minneapolis Viewpoint initialViewpoint(Envelope(-10995912.335747, 5267868.874421, -9880363.974046, 5960699.183877, SpatialReference::webMercator())); m_map->setInitialViewpoint(initialViewpoint); // Add a GraphicsOverlay GraphicsOverlay* overlay = new GraphicsOverlay(this); m_mapView->graphicsOverlays()->append(overlay); // Add a Point Graphic SimpleMarkerSymbol* sms = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("red"), 5.0f /*size*/, this); m_inputGraphic = new Graphic(this); m_inputGraphic->setSymbol(sms); overlay->graphics()->append(m_inputGraphic); // Set map to map view m_mapView->setMap(m_map); // Set up callout data m_calloutData = m_mapView->calloutData(); m_calloutData->setTitle(QStringLiteral("Coordinates")); } void ProjectGeometry::onMouseClicked(QMouseEvent& event) { // get the mouse click as a point const Point originalPoint = m_mapView->screenToLocation(event.position().x(), event.position().y()); // show the clicked location on the map with a graphic m_inputGraphic->setGeometry(originalPoint); // create the output SpatialReference by specifying a well known ID (WKID) const SpatialReference spatialReference(4326); // project the web mercator point to WGS84 const Point projectedPoint = geometry_cast<Point>(GeometryEngine::project(originalPoint, spatialReference)); // update callout data m_calloutData->setLocation(originalPoint); const QString ox = QString::number(originalPoint.x(), 'f', 5); const QString oy = QString::number(originalPoint.y(), 'f', 5); const QString px = QString::number(projectedPoint.x(), 'f', 5); const QString py = QString::number(projectedPoint.y(), 'f', 5); m_calloutData->setDetail(QString("Original: %1, %2\nProjected: %3, %4").arg(ox, oy, px, py)); m_calloutData->setVisible(true); }