diff --git a/include/geojson.h b/include/geojson.h
new file mode 100644
index 00000000..ef6aee44
--- /dev/null
+++ b/include/geojson.h
@@ -0,0 +1,137 @@
+/*! \file */ 
+#ifndef _GEOJSON_H
+#define _GEOJSON_H
+
+/*
+	GeoJSON writer for boost::geometry objects, using RapidJSON.
+	This isn't core tilemaker functionality but helps with debugging.
+	As yet it only outputs (Multi)Polygons but can be extended for more types.
+
+	Example:
+		auto gj = GeoJSON()
+		gj.addGeometry(myMultiPolygon);
+		gj.finalise();
+		std::cout << gj.toString() << std::endl;
+
+	Or use gj.toFile("output.geojson") to write to file.
+	Calling finalise(true) will 'unproject' Y values (i.e. latp2lat).
+
+	Todo: support more geometries, set/write properties.
+*/
+
+#include <iostream>
+#include <math.h>
+#include "geom.h"
+
+#include "rapidjson/document.h"
+#include "rapidjson/writer.h"
+#include "rapidjson/stringbuffer.h"
+#include "rapidjson/filewritestream.h"
+
+typedef boost::variant<Point,Linestring,MultiLinestring,Polygon,MultiPolygon,Ring> AnyGeometry;
+
+using namespace rapidjson;
+
+struct GeoJSON {
+	Document document;
+	std::vector<AnyGeometry> geometries;
+
+	GeoJSON() {
+		document.SetObject();
+		document.AddMember("type", Value().SetString("FeatureCollection"), document.GetAllocator());
+	}
+	void addGeometry(AnyGeometry geom) {
+		geometries.emplace_back(geom);
+	}
+	struct SerialiseGeometry {
+		Value *obj;
+		Document::AllocatorType *alloc;
+		bool unproject;
+
+		SerialiseGeometry(Value *obj, Document::AllocatorType *alloc, bool unproject) : 
+			obj(obj), alloc(alloc), unproject(unproject) {}
+
+		double deg2rad(double deg) { return (M_PI/180.0) * deg; }
+		double rad2deg(double rad) { return (180.0/M_PI) * rad; }
+		double latp2lat(double latp) { return rad2deg(atan(exp(deg2rad(latp)))*2.0)-90.0; }
+		Value ringToArray(Ring &r) {
+			Value arr(kArrayType);
+			for (auto &point : r) {
+				Value pt(kArrayType);
+				pt.PushBack(point.x(), *alloc);
+				pt.PushBack(unproject ? latp2lat(point.y()) : point.y(), *alloc);
+				arr.PushBack(pt, *alloc);
+			}
+			return arr;
+		}
+		void operator()(Point &p) {} // todo
+		void operator()(Linestring &ls) {} // todo
+		void operator()(MultiLinestring &mls) {} // todo
+		void operator()(Ring &r) {
+			Value coordinates(kArrayType);
+			coordinates.PushBack(ringToArray(r), *alloc);
+			obj->AddMember("coordinates", coordinates, *alloc);
+			obj->AddMember("type", Value().SetString("Polygon"), *alloc);
+		}
+		void operator()(Polygon &p) {
+			Value coordinates(kArrayType);
+			coordinates.PushBack(ringToArray(p.outer()), *alloc);
+			for (auto &inner : p.inners()) {
+				coordinates.PushBack(ringToArray(inner), *alloc);
+			}
+			obj->AddMember("coordinates", coordinates, *alloc);
+			obj->AddMember("type", Value().SetString("Polygon"), *alloc);
+		}
+		void operator()(MultiPolygon &mp) {
+			Value coordinates(kArrayType);
+			for (auto &polygon : mp) {
+				Value polyCoords(kArrayType);
+				polyCoords.PushBack(ringToArray(polygon.outer()), *alloc);
+				for (auto &inner : polygon.inners()) {
+					polyCoords.PushBack(ringToArray(inner), *alloc);
+				}
+				coordinates.PushBack(polyCoords, *alloc);
+			}
+			obj->AddMember("coordinates", coordinates, *alloc);
+			obj->AddMember("type", Value().SetString("MultiPolygon"), *alloc);
+		}
+	};
+	void finalise(bool unproject = false) {
+		Value features(kArrayType);
+		for (AnyGeometry &g : geometries) {
+			// type
+			Value obj(kObjectType);
+			obj.AddMember("type", Value().SetString("Feature"), document.GetAllocator());
+			// properties (todo)
+			Value properties(kObjectType);
+			obj.AddMember("properties", properties, document.GetAllocator());
+			// geometry
+			Value geometry(kObjectType);
+			boost::apply_visitor(SerialiseGeometry(&geometry, &(document.GetAllocator()), unproject), g);
+			obj.AddMember("geometry", geometry, document.GetAllocator());
+			// add to list
+			features.PushBack(obj, document.GetAllocator());
+		}
+		document.AddMember("features", features, document.GetAllocator());
+		geometries.clear();
+	}
+	std::string toString() {
+		StringBuffer buffer;
+		Writer<StringBuffer> writer(buffer);
+		writer.SetMaxDecimalPlaces(5);
+		document.Accept(writer);
+		std::string json(buffer.GetString(), buffer.GetSize());
+		return json;
+	}
+	void toFile(std::string filename) {
+		auto fp = std::fopen(filename.c_str(), "w");
+		char writeBuffer[65536];
+		FileWriteStream os(fp, writeBuffer, sizeof(writeBuffer));
+		Writer<FileWriteStream> writer(os);
+		writer.SetMaxDecimalPlaces(5);
+		document.Accept(writer);
+		fclose(fp);
+	}
+};
+
+#endif //_GEOJSON_H