Looking at the Vigilant TMG training manual, the doghouse is just part of the 'fly off the map' approach used by the VGS.
They use 1/4 mill charts and mark the following on it: start point, fixes, turning points, doghouse (Mag heading, mag track, leg altitude), clock marks and fuel circles (fuel remaining and fuel required to divert with reserve).
That all slots in with the use of MDR for calculatng drift, groundspeed etc.