I think the question has to be broken into two parts, which is what your topic-starting post does to a certain extent.
1. Are compasses present in Middle-Earth?
2. If compasses are present, would Rangers use them?
Harper wrote:The Numenoreans were known for their sailing abilities and their colonial expansion. Personally, I would equate their maritime technology to our Age of Exploration (or even beyond). I think that they certainly would have had celestial navigation instruments as well as some notion of latitude. Do you think that they would have had compasses? Sunstones? As their direct descendants (and recollecting that Elendil, et al. arrived on ships), is it reasonable to assume that this knowledge was retained? In addition lets remeber that Gondor had a formidable Narvy (at least at times). As a maritime power, is it reasonable to assume that such technology was used by them?
Before the introduction of the magnetic compass to Europe, the Vikings were thought to have some navigational tools. The
Uunartoq dial may have been used to determine latitude, and sunstones are said to have been used to navigate by sunlight on cloudy days in the Viking sagas. It's also thought that sunstones would have been effective even into the twilight hours. That, in combination with the long days of the summer raiding season at northern latitudes would have made them potentially very usable. Interestingly,
a piece of Icelandic spar was found on the wreck of a late 16th century sailing vessel near other navigational instruments, and it has been suggested that it was used for navigation due to the possibility of magnetic interference from the large metal guns on board. This suggests that knowledge of the use of sunstones may have been retained by sailors for hundreds of years.
The
compasses used during the 16th century aboard ships consisted of a large magnetized needle attached to the underside of a card, on which the compass rose was drawn. This supported by gimbals so the card would stay level, and all of this was attached inside a large wooden box that was attached to the deck in front of the helm. If the Numenoreans used this sort of magnetic compass, it would have to be greatly streamlined to be useful to a Ranger in the woods.
Harper wrote:If Hobbits had clocks, I think that it is very likely that compasses were also around. Also, let's not forget the "marvelous" toys which were passed out at the party--I always got the impression that thy were "mechanical". I don't imagine that jewelers would have a problem making a simple case for a compass. We know that there was jewelry. So, I think the ability to make the "case" portion of a pocket compass was definitely there and obtainable.
I've always been under the impression that the hobbits of the Shire have a level of technology that is comparable to 18th century, or maybe early 19th century. They have clocks, umbrellas, and pockets. This would suggest that they might have the technological level to make compasses, but they might not have had the need. The hobbits of the Shire don't seem to roam far, and "maps made in the Shire showed mostly white spaces beyond its borders" (FotR: Chapter 2, The Shadow of the Past).
Harper wrote:An example would be the "compass rose" which appears at the top of most of the maps.
I don't know that we can take this as evidence for compasses in Middle-Earth. It would depend on whether Tolkien was just providing a map for the convenience of the reader, or if he was recreating an artifact of Middle-Earth. It gets pretty meta pretty quickly...
Elleth wrote:I confess, I don't see brass compasses like colonial / civil war reenactors carry in a Ranger's kit: the design aesthetic is just so early-modern (Hobbits maybe?)
If you're interested in a little different aesthetic, the
Lewis and Clark compass has a slightly different look.
So, could there be compasses in Middle-Earth? Maybe! (Very helpful, right?) It certainly doesn't seem outside the realm of possibility.
Second question - If compasses are present, would Rangers use them?
Honestly, I feel like that is even more unclear. Aragorn is obviously the Ranger that we know the most about. He is described by Gandalf as "the greatest traveller and huntsman of this age of the world" (FotR: Chapter 2, A Shadow of the Past). In the Chetwood, he is described as leading the hobbits "confidently among the many crossing paths, although left to themselves they would soon have been at a loss. He was taking a wandering course with many turns and doublings, to put off any pursuit" (FotR: Capter 11, A Knife in the Dark). No mention of any navigational tool is made.
The Rangers are also thought to have supernatural abilities by the people of Bree. They "were believed to have strange powers of sight and hearing, and to understand the languages of beasts and birds" (FotR: Capter 9, At the Sign of the Prancing Pony). It's been suggested elsewhere on the forum that these abilities could be those of highly skilled woodsmen misunderstood. Navigating the wilderness without tools could play into that.
Now, it's possible that Aragorn has more knowledge of the geography of Middle-Earth than the "average" ranger (if there is such a thing). He was fostered in Rivendell, and "There are many maps in Elrond's house" (FotR: Chapter 3, The Ring Goes South). He may have a more complete mental map, and therefore may not need navigational aids where other rangers might.
Personally, a compass doesn't totally fit in with my mental image of a ranger, but that's just the idea of a ranger I have in my head. For safety reasons, I certainly don't think anyone would argue against carrying a compass, authentic or not.