I have been reviewing the forum posts on converting coordinate systems but I am still confused.

I am trying to convert the coordinate system of a QGraphicScene (physical) into geographic (latitude, longitude). This is so I can move my airplane object by latitude, longitude.

Currently I have code that creates the graphic item and will move it within the physical points but I’m not sure how/where to set the Window coordinates to get it to move on latitude, longitude. If you notice in my code I tried on the painter object and that didn’t work.

Can anyone help?

Qt Code: 
  1. //-----------------------------------------------------------------------------------
  2.  
  3. class CMapView : public QGraphicsView
  4. {
  5.   Q_OBJECT
  6.  
  7. public:
  8.   CMapView(QWidget * parent = 0);
  9. };
  10.  
  11. CMapView::CMapView(QWidget * parent)
  12.   : QGraphicsView(parent)
  13. {
  14.   setDragMode( ScrollHandDrag );
  15. }
  16.  
  17.  
  18. //-----------------------------------------------------------------------------------
  19.  
  20. CFlightPath : public QMainWindow
  21. {
  22.   Q_OBJECT
  23.  
  24. public:
  25.   CFlightPath();
  26.  
  27. private slots:
  28.  
  29. protected:
  30.   void placeAircraft();
  31.  
  32.   QGraphicsScene * scene;
  33.   CMapView * view;
  34. };
  35.  
  36. CFlightPath::CFlightPath()
  37. {
  38.   scene = new QGraphicsScene(0,0,400,400);
  39.  
  40.   placeAircraft();
  41.  
  42.   view = new CMapView();
  43.   view->setScene(scene);
  44.  
  45.   setCentralWidget(view);
  46.  
  47.   setWindowTitle("Flight Path");
  48.  
  49.   mainClose   = false;
  50. }
  51.  
  52. void CFlightPath::placeAircraft()
  53. {
  54.   CAircraft * airplane = new CAircraft();
  55.   ownship->setPos( 200, 300 );
  56.  
  57.   scene->addItem( airplane );
  58. }
  59.  
  60. //-----------------------------------------------------------------------------------
  61.  
  62. class CAircraft : public QObject, public QGraphicsItem
  63. {
  64.   Q_OBJECT
  65.  
  66. public:
  67.   CAircraft();
  68.  
  69.   QRectF boundingRect() const;
  70.   void paint(QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * widget);
  71.  
  72. private slots:
  73.   void moveAircraft();
  74.  
  75. private:
  76.   QPainterPath shape;
  77.  
  78.   QTimer * updateTimer;
  79.  
  80.   float xPos, yPos, deg, prevDeg;
  81.   int count;
  82. };
  83.  
  84.  
  85. CAircraft::CAircraft()
  86. {
  87.   double localX = -24.0;
  88.   double localY = -14.0;
  89.  
  90.   QPolygonF aircraft;
  91.  
  92.   aircraft << QPointF( (localX+24.0), (localY+0.0) )
  93. 	  << QPointF( (localX+25.0), (localY+1.0) )
  94. 	  << QPointF( (localX+26.0), (localY+2.0) )
  95. 	  << QPointF( (localX+27.0), (localY+3.0) )
  96. 	  << QPointF( (localX+27.0), (localY+9.0) )
  97. 	  << QPointF( (localX+32.0), (localY+9.0) )
  98. 	  << QPointF( (localX+32.0), (localY+8.0) )
  99. 	  << QPointF( (localX+35.0), (localY+8.0) )
  100. 	  << QPointF( (localX+35.0), (localY+9.0) )
  101. 	  << QPointF( (localX+38.0), (localY+9.0) )
  102. 	  << QPointF( (localX+38.0), (localY+8.0) )
  103. 	  << QPointF( (localX+41.0), (localY+8.0) )
  104. 	  << QPointF( (localX+41.0), (localY+9.0) )
  105. 	  << QPointF( (localX+47.0), (localY+9.0) )
  106. 	  << QPointF( (localX+48.0), (localY+10.0) )
  107. 	  << QPointF( (localX+47.0), (localY+11.0) )
  108. 	  << QPointF( (localX+36.0), (localY+13.0) )
  109. 	  << QPointF( (localX+27.0), (localY+16.0) )
  110. 	  << QPointF( (localX+26.0), (localY+31.0) )
  111. 	  << QPointF( (localX+30.0), (localY+31.0) )
  112. 	  << QPointF( (localX+31.0), (localY+32.0) )
  113. 	  << QPointF( (localX+25.0), (localY+34.0) )
  114. 	  << QPointF( (localX+23.0), (localY+34.0) )
  115. 	  << QPointF( (localX+17.0), (localY+32.0) )
  116. 	  << QPointF( (localX+18.0), (localY+31.0) )
  117. 	  << QPointF( (localX+22.0), (localY+31.0) )
  118. 	  << QPointF( (localX+21.0), (localY+16.0) )
  119. 	  << QPointF( (localX+12.0), (localY+13.0) )
  120. 	  << QPointF( (localX+1.0), (localY+11.0) )
  121. 	  << QPointF( (localX+0.0), (localY+10.0) )
  122. 	  << QPointF( (localX+1.0), (localY+9.0) )
  123. 	  << QPointF( (localX+7.0), (localY+9.0) )
  124. 	  << QPointF( (localX+7.0), (localY+8.0) )
  125. 	  << QPointF( (localX+10.0), (localY+8.0) )
  126. 	  << QPointF( (localX+10.0), (localY+9.0) )
  127. 	  << QPointF( (localX+13.0), (localY+9.0) )
  128. 	  << QPointF( (localX+13.0), (localY+8.0) )
  129. 	  << QPointF( (localX+16.0), (localY+8.0) )
  130. 	  << QPointF( (localX+16.0), (localY+9.0) )
  131. 	  << QPointF( (localX+21.0), (localY+9.0) )
  132. 	  << QPointF( (localX+21.0), (localY+3.0) )
  133. 	  << QPointF( (localX+22.0), (localY+2.0) )
  134. 	  << QPointF( (localX+23.0), (localY+1.0) );
  135.  
  136.   shape.addPolygon( aircraft );
  137.  
  138.   setFlag(ItemIgnoresTransformations, true);
  139.  
  140.   updateTimer = new QTimer();
  141.   updateTimer->setInterval( 50 );
  142.   connect( updateTimer, SIGNAL(timeout()), this, SLOT(moveAircraft()));
  143.   updateTimer->start();
  144.  
  145.   xPos = 200.0;
  146.   yPos = 300.0;
  147.   deg = 270.0;
  148.   prevDeg = 0.0;
  149.   count = 0;
  150. };
  151.  
  152. QRectF CAircraft::boundingRect() const
  153. {
  154.   return QRectF(-24,-14,48,34);
  155. }
  156.  
  157. void CAircraft::paint(QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * /*widget*/)
  158. {
  159.   painter->setWindow(-100,-100, 200, 200);
  160.  
  161.   painter->fillPath( shape, Qt::darkGray );
  162. }
  163.  
  164. void CAircraft::moveAircraft()
  165. {
  166.   float x, y;
  167.  
  168.   if ( count < 50 )
  169.     xPos -= 1.0;
  170.   else if (count < 100 )
  171.     yPos += 1.0;
  172.   else if (count < 150 )
  173.     xPos += 1.0;
  174.   else if (count < 200 )
  175.     yPos -= 1.0;
  176.   else if (count < 250 )
  177.     {
  178.       yPos += 1.0;
  179.       xPos -= 1.0;
  180.     }
  181.   else if (count < 300 )
  182.     {
  183.       yPos -= 1.0;
  184.       xPos += 1.0;
  185.     }
  186.  
  187.   count++;
  188.  
  189.   x = xPos;
  190.   y = yPos;
  191.  
  192.   setPos(x, y);
  193. }
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