anchor.diff:  Point dakar = geo.makePoint(-17.45, 14.69);
   ----
   
  -=== Writing WKT
  +Circles and rectangles are also supported, polygons require JTS to be present.
   
  -RDF4j 2.1.x uses Spatial4J 0.4.1, which does not support writing shapes to WKT just yet (added in 0.5).
  -
  -An extremely simple writer could look like:
  -
  -[source,java]
  -----
  -public static String toWkt(Point p) {
  -   return "POINT(" + p.getX() + " " + p.getY() + ")";
  -}
  -----
  -
  -== Queries
  +=== Distance query
   
   Using the function described above, the coordinates can be added to subjects.
   
  
positive.code: = GeoSPARQL
  
  (Work in progress)
  
  == WKT Literals
  
  Geographic coordinates can be stored as literals with the "Well-Known Text" (WKT) datatype. WKT allows for very simple, i.e. a single point, but also very complex shapes, e.g. shapes consisting of multiple polygons. 
  
  === Order of coordinates
  
  WKT can also describe coordinate reference systems (CRS) and projections. 
  One common source of confusing is that, by default, the X-coordinate (longitude)is followed by Y-coordinate (latitude) while many people are used to the Y-X (latitude-longitude) notation.
  
  Spatial4j provides some convenient functions to generate geometric shapes.
  For instance, a series of points representing the center of the cities of Amsterdam, Brussels... can easily be generated using `SpatialContext.GEO`.
  
  [source,java]
  ----
  
negative.code: Make sure to include the rdf4j-queryalgebra-geosparql jar in your project.
  
  The following query returns the distance between city centers in kilometers.
  `GEOF` provides geometric functions, while `UOM` provides unit of measurements.
  Note that the metric unit is spelled `metre` (not the US spelling `meter`)
  
  [source,java]
  ----
  