Mathematical model

Hi all.

I would like to know what is your point of view in regard of building mathematical model on DP. Common practice is that any vessel is to stay outside 500m zone for usually 30 mins to allow the model to build up. Fine, but during that stage sometimes I am witness of different practices made by different DPO’s.

The question is - shall the vessel stay still on AUTOPOS waiting 30 mins, or meanwhile she can start making her way on full DP to the location, ie. with slow speed 0.2kn? Theoreticaly such a small movement shouldn’t significantly affect sea forces calculations. When the vessel is not moving for 30 mins then definitely it would provide decent model to have, but some clients insist to come closer asap to not waste a time…

Secondly, lets consider such a typical scenario - during the job, all is working good, but vessel has to step off the platform let’s say 100m and for some reason this has to be done quickly as per request. We deselect one axis (surge) then move away. How about the mathematical model then? Is it really gone? Some people move back to the installation after another 30mins on full DP but other DPO’s don’t wait and just return to original location instantly when it is permitted by 2nd party.

Thanks for your answers.