Description: Nowadays, on the land management field, everybody heard about Geographical Information Systems (GIS). But yet, the meaning that everyone gives to the GIS is different, according to the use they do. The main obstacles on learning SIG in its entirety are: the complexity of the tool and the institutional duty to use it. We have looked how a continuing vocational training in GIS starts: we have noticed that, from the beginning, a conflict of interests take place between trainees (came to learn to use a computerized tool for specific tasks) and the trainer who place theoretical knowledge on the heart of the training process. How trainers manage the training process? Which abilities they mobilize to spur on the trainees, to determine them to learn entirely GIS instrument and not only some specific technical operations? We analyse the first moments of two training sessions. We try to notice which role the trainers have on the involvement of the trainees in the cognitive process. How trainers offer learning conditions for both theoretical and practical aspects? Methodology: Full training sessions (30 hours each one) have been video recorded, transcribed and analysed using analysing tools offered by didactics and mainly by vocational didactics. We have been chosen to lean on the theoretical field of the conceptualization as a condition in problem solving. On the vocational didactics field, we have been used theories of Lev Vygotski (Zone of Proximal Development), Jerome Bruner (Scaffolding) Gérard Vergnaud (operative form of the knowledge) and Patrick Mayen (developmental potential situation). We also have been taken into account the point of view of Guy Brousseau and his concept of didactical situation. Conclusions: We aim for two kinds of results. First one concerns work analysis of the trainers in continuing vocational education. We introduce self-didactisation to indicate what a trainer does when he uses trainees' experience as didactical tool : share experiential knowledge, but also encourage people to think about what they have to do in their present tasks, what they'll have to do and what they may have to do in the future. Concerning the theoretical results, we identify some elements which could open the discussion about the theoretical difference between didactics and vocational didactics: which difference/similarity between the contract proposed by the trainer to the trainees and the didactical contract introduced by Brousseau for compulsory education?