Notes to self on web map-style tree viewers. The basic idea is to use Google Maps or Leaflet to display a tree. Hence we need to compute tiles. One approach is to use a database that supports spatial queries to store the x,y coordinates of the tree. When we draw a tile we compute the coordinates of that tile, based on position and zoom level, do a spatial query to extract all lines that intersect with the rectangle for that tile, and draw those.