topic Re: Transform a Point into a Polygon (Square) in ArcGIS Runtime SDK for Android Questions

Transform a Point into a Polygon (Square)

GuilhermeFernandes — Tue, 16 Feb 2021 15:25:05 GMT

Hello. I am having trouble to implementing a new functionality in my application.

Based on a point (latitude and longitude), I want that this point automatically transform into a square, with this lat and long as the center. I'm trying something like this to transform the point:

double ang__ = 0;
double co_x1 = (sin(toRadians(ang__ + 90)) * widthImplement) + point.getX();
double co_y1 = (cos(toRadians(ang__ + 90)) * widthImplement) + point.getY();
double co_x2 = (sin(toRadians(ang__ + 270)) * widthImplement) + point.getX();
double co_y2 = (cos(toRadians(ang__ + 270)) * widthImplement) + point.getY();

But it's not working.

Has anyone already done something like that?
Note: I would like to present width options for this square on the screen.

Re: Transform a Point into a Polygon (Square)

MarkBaird — Tue, 16 Feb 2021 17:40:05 GMT

You will find it much easier if you convert your point which you want as the centre of your square into a projected coordinate system. Once you've done that you can offset in metres from the location and things are much easier to understand.

SimpleLineSymbol simpleLineSymbol = new SimpleLineSymbol(SimpleLineSymbol.Style.SOLID, 0xFF00FF00, 3); // a point in a field near London, UK wgs84Point = new Point(0,51, SpatialReferences.getWgs84()); // convert wgs84 (lat / long) into projected coordinate system Point wmPoint = (Point) GeometryEngine.project(wgs84Point, SpatialReferences.getWebMercator()); // size of your square in metres double size = 100; // easier logic for point of square with offsets in metres Point p1 = new Point(wmPoint.getX() + (size / 2), wmPoint.getY() + (size /2), SpatialReferences.getWebMercator()); Point p2 = new Point(wmPoint.getX() + (size / 2), wmPoint.getY() - (size /2), SpatialReferences.getWebMercator()); Point p3 = new Point(wmPoint.getX() - (size / 2), wmPoint.getY() - (size /2), SpatialReferences.getWebMercator()); Point p4 = new Point(wmPoint.getX() - (size / 2), wmPoint.getY() + (size /2), SpatialReferences.getWebMercator()); // make polygon from points PointCollection pointCollection = new PointCollection(SpatialReferences.getWebMercator()); pointCollection.add(p1); pointCollection.add(p2); pointCollection.add(p3); pointCollection.add(p4); Polygon square = new Polygon(pointCollection); // Graphic and add to graphics overlay to display it Graphic squareGraphic = new Graphic(square, simpleLineSymbol); graphicsOverlay.getGraphics().add(squareGraphic);

Not a pretty bit of code, but it should point you in the right direction.

Does this help

Re: Transform a Point into a Polygon (Square)

GuilhermeFernandes — Fri, 19 Feb 2021 12:40:48 GMT

Thank you so much Mark. Worked perfectly.