How to Use the Geometry Layer

PTV xMap Server allows custom vector objects to be drawn on your maps by adding the so called GeometryLayer. In this tutorial we show you how to use a GeometryLayer and how to define vector shapes.

Well-known text (WKT)

WKT is a textual markup language that allows you to specify vector objects on a map. The most important WKT object types are points ( POINT ), lines ( LINESTRING ) and polygons ( POLYGON ). Below you find a short introduction into the WKT format.

Point

A point is declared with the keyword POINT followed by its X- and Y- coordinates which are separated by a space and surrounded by parenthesis. Please notice following example:

POINT(800000.0 6900000.0)

Line

A line is declared with the keyword LINESTRING followed by a list of comma separated points. Please notice following example:

LINESTRING(800000 6860000, 800000 6880000, 900000 6880000, 900000 6860000)

Area / Polygon

A polygon is defined by a list of so called LinearRings, which are lists of points where the first and the last point are the same. If you define a polygon with only one LinearRing, you get a simple polygon with the LinearRing's points as verticals. However, if you create a polygon with more than one LinearRing, then the additional LinearRing(s) can be used to define holes within the original polygon (provided the second polygon lies within the first one).

Simple Polygon in shape of a triangle:

POLYGON( (800000 6900000, 900000 6900000, 850000 7000000, 800000 6900000) )

Polygon in shape of a triangle but with one hole:

POLYGON( (800000 6900000, 900000 6900000, 850000 7000000, 800000 6900000),
(830000 6910000, 870000 6910000, 850000 6950000, 830000 6910000) )

Click here for additional information on WKT.

Using WKT to define shapes

Java snippet

Define at first both polygons. As second step create two objects as type of Geometry setting the polygons with further relevant properties.

Step 1:

Polygon polygon1 = new Polygon();
polygon1.setWkt("POLYGON((800000 6860000, 800000 6880000, 900000 6880000, 900000 6860000,
800000 6860000)" + ",(820000 6862000, 820000 6868000, 880000 6868000,
880000 6862000, 820000 6862000))");

Polygon polygon2 = new Polygon();
polygon2.setWkt("POLYGON((800000 6900000, 900000 6900000, 850000 7000000, 800000 6900000)" +
",(830000 6910000, 870000 6910000, 850000 6950000, 830000 6910000))");

Step 2:

Geometry geometry1 = new Geometry();
geometry1.setDescription("firstPolygon");
geometry1.setId(0);
geometry1.setGeometry(polygon1);
geometry1.setReferencePoint(point);

Geometry geometry2 = new Geometry();
geometry2.setDescription("secondPolygon");
geometry2.setId(1);
geometry2.setGeometry(polygon2);
geometry2.setReferencePoint(point);
);

Setting the shape's style with GeometryOptions

GeometryOptions allow you to alter the appearance of the drawn shapes. You can define such properties as line color, fill color and transparency. For a complete list of options see the list below or read the PTV xMap Server API on this topic.

GeometryOptions are always applied to a group of Geometry objects called Geometries. If you have multiple Geometry objects and want to apply different styles you have to group them into different Geometries.

List of available options

All colors are 24-bit RGB values. If you have 8-bit red, green and blue values, the color value equals as follows:
blue*216 + green*28 + red

Step 1: Define a new method with RGB values.

Java snippet

// helper method to calculate the color
private static String rgbToColorString(int red, int green, int blue) {
int color = (blue<<16)+(green<<8)+(red);
return ""+color;
}

Step 2: Create geometryOptions and set some properties:

Java snippet

// set some geometry options to alter the appearance of the shapes
GeometryOption[] geometryOptions = new GeometryOption[]{
new GeometryOption(GeometryOptions.BORDERCOLOR, rgbToColorString(0,128,255)),
new GeometryOption(GeometryOptions.FILLCOLOR, rgbToColorString(255,0,0)),
new GeometryOption(GeometryOptions.FILLALPHA, "200"), // 0-255
new GeometryOption(GeometryOptions.AUTOCENTEROBJECTS, "1") // 0-255
};

Step 3: At least put both objects into the new instantiated array derived from the class Geometries[ ].

Java snippet

// bundle geometries with geometry options
Geometries geometries = new Geometries(new Geometry[]{ geometry1, geometry2},
geometryOptions);

Defining a GeometryLayer

Finally, the class GeometryLayer is defined including relevant properties in order to display the shape of the given object. Due to the opportunity to define several layers such as CustomerLayer or GeometryLayer an individual name and a corresponding draw priority should be defined.

The range of the draw priority is from 0 (minimum priority => drawn underneath all other layers) to 50000 (maximum priority => drawn above all other layers). The detailed information is added to the PTV xMap API documentation.

Also the object information is available such as the real or pixel coordinates. Set the objectInfos property whether it is needed for further actions. If ObjectInfoType.GEOMETRY is added the coordinates of each point from the above defined shape will be output in the result list. Further properties and their meaning are also documented in the PTV xMap API documentation.

Add layer as a new GeometryLayer object and set name, geometries, draw priorities, visibility and object information.

Java snippet

public static final int PRIORSTREET=150;

// put the geometries into a layer
GeometryLayer layer = new GeometryLayer();
layer.setName("geomLayer");
layer.setDrawPriority(DrawPriorities.PRIORSTREET);
layer.setVisible(true);
layer.setGeometries(new Geometries[]{geometries});
layer.setObjectInfos(ObjectInfoType.GEOMETRY);

Source Code

The example mapping with GeometryLayer is also executable as a stand-alone java program.

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