--- a/pkg/octree/tin.go	Sun Dec 30 16:24:51 2018 +0100
+++ b/pkg/octree/tin.go	Mon Dec 31 11:13:49 2018 +0100
@@ -32,15 +32,24 @@
 	errTooLessPoints = errors.New("Too less points")
 )
 
+// Tin stores a mesh of triangles with common vertices.
 type Tin struct {
-	EPSG      uint32
-	Vertices  []Vertex
+	// EPSG holds the projection.
+	EPSG uint32
+	// Vertices are the shared vertices.
+	Vertices []Vertex
+	// Triangles are the triangles.
 	Triangles [][]int32
 
+	// Min is the lower left corner of the bbox.
 	Min Vertex
+	// Max is the upper right corner of the bbox.
 	Max Vertex
 }
 
+// FromWKB constructs the TIN from a WKB representation.
+// Shared vertices are identified and referenced by the
+// same index.
 func (t *Tin) FromWKB(data []byte) error {
 	log.Printf("info: data length %d\n", len(data))
 
@@ -201,6 +210,8 @@
 	loadTinByIDSQL = tinSQLPrefix + `WHERE id = $2` + tinSQLSuffix
 )
 
+// GenerateTinByID generated a TIN by triangulating a point cloud
+// from the database.
 func GenerateTinByID(
 	ctx context.Context,
 	conn *sql.Conn,
@@ -219,6 +230,7 @@
 	return &tin, nil
 }
 
+// Scan implements the sql.Scanner interface.
 func (t *Tin) Scan(raw interface{}) error {
 	if raw == nil {
 		return nil