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 originalGeometry
and aSpatialReference
to 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
#include "ProjectGeometry.h"
#include "Map.h"
#include "MapQuickView.h"
#include "Basemap.h"
#include "Viewpoint.h"
#include "Envelope.h"
#include "GeometryEngine.h"
#include "Point.h"
#include "SimpleMarkerSymbol.h"
#include "Graphic.h"
#include "GraphicsOverlay.h"
#include "CalloutData.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.x(), event.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 = 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);
}