Showing maps and borders in Processing
A few days ago, I posted a video showing public procurement expanding geopraphically with the EU enlargements in the ’00s. There weren’t any borders, but you could sort of see the outline of Europe and how the dots spread east with time.
Adding actual borders to the map proved very frustrating. The Geographical Information System (GIS) space seems plagued by obtuse binary formats, stodgy desktop applications and a profusion of coordinate systems. I tried many avenues, one of the more promising being a smoothed map from MapShaper passed through TatukGIS and exported to KML. The coordinates from MapShaper turned out to be incompatible with the latitude/longitude ones I had from the Google Maps web services however.
After much searching, I found a KML-file in the Google Maps group (worldcountriesKML.zip) with the borders of all the worlds countries. It’s not smoothed in any way, so the haggard coastline of a country like Norway looks too thick when zoomed out. The result is better than the original though:
I implemented a simple Processing helper-class to parse and draw the KML. You instantiate it like this: helper = new XMLHelper(new XMLElement(this, "world.kml"));. It has a Init() method that takes a String[] of the countries you need and String denoting the XML path to the line coordinates, e.g. "Polygon/outerBoundaryIs/LinearRing/coordinates". After initialization you can ask it for its maximum and minimum coordinates using min_x, max_x, min_y, max_y. The Draw() method draws the map on the sceen, scaled to fit the size.
class XMLHelper
{
float coordscale = 1;
XMLElement borders;
Line[] lines = new Line[0];
public float max_y =0, min_y = 70, max_x = 0, min_x = 0;
public XMLHelper(XMLElement xe)
{
borders = xe;
}
public void Init(String[] wantedcountries, String coordpath)
{
XMLElement[] filecountries = borders.getChildren("Folder/Placemark");
for(int i = 0; i < filecountries.length; i++)
{
XMLElement c = filecountries[i];
if(Util.Contains(wantedcountries, c.getChild(0).getContent()))
{
// this one should be included on the map
String points = c.getChild(coordpath).getContent();
String[] point_a = split(points," ");
Point[] pointarray = new Point[point_a.length];
for(int j = 0; j < point_a.length; j++)
{
String[] xyz = split(point_a[j],',');
float x = float(xyz[0])/coordscale;
float y = float(xyz[1])/coordscale;
pointarray[j] = new Point(x, y);
max_x = max(x, max_x);
min_x = min(x, min_x);
max_y = max(y, max_y);
min_y = min(y, min_y);
}
// this looks slow
lines = (Line[]) append(lines,new Line(pointarray));
}
}
}
public void Draw()
{
for(int i = 0; i < lines.length; i++)
{
Line l = lines[i];
beginShape();
for(int j = 0; j < l.points.length; j++)
{
vertex(
map(l.points[j].x, min_x, max_x, 0, width),
height - map(l.points[j].y, min_y, max_y, 0, height)
);
}
endShape();
}
}
}
class Point
{
public float x,y;
public Point(float _x, float _y)
{
x = _x;
y = _y;
}
}
class Line
{
Point[] points;
public Line(Point[] _points)
{
points = _points;
}
}
static class Util
{
static boolean Contains(String[] a, String s)
{
for(int i = 0; i < a.length; i++)
{
if(a[i].toLowerCase().equals(s.toLowerCase()))
{
return true;
}
}
return false;
}
}