That's a smidge earlier than my primary area of interest, and I'm no cartographer, but this page from the British Library gives some food for thought as well as some linked pages that may shed more light, but the overall gist is that, generally, Medieval maps were utilitarian: often designed more with the idea of showing you what's between, or how to get from, point A and point B, rather than detailed images of large areas from which people could glean whatever information they could. Some of the maps depicted this page of regional maps and this page of city maps also seem to support this idea: it's not detailed cartography, things aren't necessarily to scale, but it's enough to get you pointed in the right direction and shows some major features to help you get your bearings and keep you going.