I can't identify terrain with any certainty unless it's visible (i.e. lit up, but not the grey scale memory). I can see some heath and I can see something that's coniferous, but I'm always uncertain about whether it's forest or mire in that case. I use the looking function to identify the terrain of locations of interest.
Given how few heath locations there are, it ought to be fairly easy to look at each of them and find the ones that have coniferous forest to the north of them (where the shelter should actually be) and walk into those few tiles from the heath tiles (you might even walk to each heath tile regardless, given how few there are). I've never had any trouble finding the blood scapes by walking through a tile they're present in (zooming in and then out can easily miss them in coniferous tree infested terrain).
In order to actually see each heath terrain tile and identify it and its norther partner may require you to walk there to get close enough to see them on the overmap.
Also, the F6 map is crucial to identify which terrain is within the search area rather than outside of it.
Another search method is to just walk across the overmap from each side to the other in a line, shift the line one step, and repeat until the whole area is covered, identifying the terrain of every tile that might be of interest (and its partner to the north/south), zooming in only on the tiles that are actually of the right type (and I would recommend zooming in on the heath tile and walk to the coniferous tile in order to reduce the risk of zooming in too close to the animal and risk triggering an immediate attack).