great-circle

MySQL OpenGIS CROSSES doesn't seem to work for me: SET @ls = 'LineString(1 1, 2 2, 3 3)'; SET @xx = 'LineString(0 2, 10 2)'; # SELECT AsText(EndPoint(GeomFromText(@ls))); select crosses(GeomFromText(@ls), GeomFromText(@xx)) returns 0 - expected 1 How would I rewrite this as a MySQL function? Bonus points for using lat, lon and spherical projection (and maybe the Great Circle.) PS I can't create tags and I have lost my old login: Useful tags would be: MySQL OpenGIS CROSSES greatcircle lat lon - :) Just use INTERSECTS(line1,line2) SET @ls = 'LineString(1 0,1 2)'; SET @xx = 'LineString(0 1, 2 1)'

I have a Latitude, Longitude, and a direction of travel in degrees true north. I would like to calculate if I will intersect a line defined by two more Lat/Lon points. I figure the two points defining the line would create my great circle and my location and azimuth would define my Rhumb line. I am only interested in intersections that will occur with a few hundred kilometers so I do not need every possible solution. I have no idea where to begin. The simple answer is yes -- if you start from any lat/lon and continue traveling along some great circle, you will eventually cross any and all