我认为值得记住的是，并非所有平面地图都是墨卡托投影.如果不特别了解该地图，很难确定.您可能会发现世界上一小部分区域的大多数地图更可能是 圆锥 类型的投影，其中地图上的感兴趣区域比全球墨卡托投影上的更平坦".离赤道越远，这一点尤其重要(而英国离它也足够远).

I think it's worthwhile to keep in mind that not all flat maps are Mercator projections. Without knowing more about that map in particular, it's hard to be sure. You may find that most maps of a small area of the world are more likely to be a conical type projection, where the area of interest on the map is "flatter" than would be on a global Mercator projection. This is especially more important the further you get away from the equator (and the UK is far enough away for it to matter).

您可以使用您正在尝试的计算获得足够接近"，但为了获得***准确性，您可能需要使用具有明确投影的地图，或者创建自己的地图.

You may be able to get "close enough" using the calculations you're trying, but for best accuracy you may want to either use a map with a well-defined projection, or create your own map.