Навигационное счисление. 3 часть. Дрейф, течения, ошибки

Everyone knows that Russia, and therefore all of us, are surrounded by enemies. So, the task is extremely simple - these same enemies have turned off our GPS. For now - only GPS, let's start with the simplest. And now, completely unexpectedly, we need, firstly, to restore the navigation service on the boat in new conditions, and, secondly, to bring the boat to its destination, in accordance with the previously planned plan. No green men can lead astray people for whom the sea is their home. Satellites are lost, we switch to the backup navigation system - the classic one. This is not an accident, so there is no reason to call rescuers. Most likely, it will not even be necessary to change the trip plan. There will be noticeably more navigation work, yes, it will turn into routine accounting work with a lot of calculations, with plotting, and constant monitoring of the course and speed in order to keep the uncertainty of our location within the bounds of decency. In addition, it will most likely be necessary to adjust the transition tactics taking into account the increased navigation errors.