This paper addresses the problem of accurate and reliable path following of a heavy industrial mobile robot evolving with centimetric accuracy requirement. For this purpose sliding estimation is a crucial issue, even more in off-road context with uneven and slippery terrains. So, we focus on position and sliding observers design in function of the distance covered, thus allowing to carry on maneuvers at any operational speed with constant accuracy. Furthermore, these observers are not affected by path tracking errors. Implementation in simulation demonstrates efficiency of such algorithms.