Sailing down the east coast we often came across Cardinal Markers that just 'didn't seem to be' of value without a chart. They make sense when approaching from the 'ideal' direction but sometimes had we not been using a chart showing the obvious obstruction I feel we could have made a mistake. I have attached an example. If we approach the East Cardinal marker from the east (Position 'A') then we are safe to pass on the east side... we cannot pass to the north or the south because we would end up on the west side (in the example shown the actual obstruction was actually on the south side of an east cardinal marker which doesn't make sense to me!). If I am not using a chart, how wide a berth or how big should the radius be if in the example my intention was to arrive at point 'X' ? (See greyed arc which I would gather would be the no go zone) Is there a standard that is used to place them a certain distance from a known obstruction or are they just not something you can navigate by without a chart? (or perhaps I am not reading them correctly?) Like I said with the luxury of a chart it is blindingly obvious but if you can imagine not having a chart I feel it could be quite confusing.