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I'm trying to come up with the D&D 3.5e world's functional equivalent to a real life Non-Directional Beacon (NDB).

Are there any existing spells in D&D 3.5e that can be cast on durable objects (say, stone monoliths) to make them into some sort of beacon that can be homed upon (or better yet, used for direction-finding purposes) from a long distance (miles, not feet) by some other means than sight (say, with the aid of a spell or magic item used or carried by whoever desires to home in on it)? Magic items are welcome instead, provided they are durable enough to survive being placed outdoors!

Source material is unrestricted save for epic level spells (a straight Wiz20, Clr20, or Drd20 should be able to make a beacon). It should cost less than constructing an inn or other permanent structure, and should not require special jewels or other exotic materials in the monolith itself. However, if the homing/direction-finding function can work over the many miles required, then the range of imbuing the object does not matter -- it's not a major problem if a touch-range spell requiring several hours of work is needed to set one of these up, as the beacon-monoliths are set-and-forget. The homing function itself, though, must be available cheaply (as a first or second level spell if not a cantrip or orison for divine casters; bonus points if it's available as an arcane spell as well); a permanent magic item is acceptable instead provided it is not bound to a specific instance of one of these beacons, small enough for a user or their mount to wear, and costs less than oh, say, 10,000gp.

Custom magic item research should not be a problem, nor is custom spell research. Houserules can be proposed here -- I'm workshopping this here because I don't know how to translate what I want from the RL terms I understand it in to something a DM who is utterly unfamiliar with the real-life IFR environs can understand.

Also, teleportation itself isn't workable (teleport isn't accessible enough, and probably has too short of a distance, besides, this needs to work on a day-in-day-out basis), and find the path may not work so well in an aerial environment (can you set up a holding fix with it?). The same accessibility argument holds for Plane Shift...

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    \$\begingroup\$ Any restrictions on source material? Spell level? Cost? Distance? Rarity? \$\endgroup\$ – Miniman Feb 3 '15 at 0:26
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    \$\begingroup\$ Are custom magic item rules allows? How strict are the house-rule options? Is spell-research allowed? \$\endgroup\$ – Brian Ballsun-Stanton Feb 3 '15 at 0:30
  • \$\begingroup\$ I meant restrictions on what is used to home in on the beacon as well as on the construction of the beacon. \$\endgroup\$ – Miniman Feb 3 '15 at 0:35
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    \$\begingroup\$ Homed in on to what end? \$\endgroup\$ – Hey I Can Chan Feb 3 '15 at 0:45
  • \$\begingroup\$ And would Plane Shift be a viable method to lock into the beacon? Because that could really affect how this Mox Beacon of yours might work. \$\endgroup\$ – Thomas Jacobs Feb 3 '15 at 0:45
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The spell "Locate City" has a range of 10 miles per caster level, and allows the sense of distance and direction to the "nearest community of a minimum size designated by you at time of casting." With nearest being counted without movement through solid objects.

Thus, with a sufficiently large caster level, a sufficiently accurate census, and a sufficiently large population density of villages and cities, it should be quite possible to get a very good idea of where a person is based on gated counts of censuses.

The trick to building a navigation network out of this is by creating artificial communities in "known positions" which count for purposes of this spell. (How to do that is functionally a DM call, but a metropolis built in great miniature with undead squirrels haunt-shifted into it to count as "occupants" suspended in the sky isn't a... horrible option.) For each of these metropoli, anchor to them to the sky via 3 immovable rods within a spacing dedicated by the modal range of the spell being used (which itself becomes a question of assets and magic item economies.)

Much like with dGPS, since you can set the community size of each of these, it turns into a 4-colour map problem equivalent. By knowing north, having a chart of these undead beacons, and casting the spell N times (where N is the set of granularities allowed for by "minimum population" in the spell), you can get a direction and distance to each of the nearest "population-unique" beacons. Then it's a matter of triangulating against the map to identify where the individual is.

Circle dance would be preferable (as it has no maximum range), save for the fact that it requires firsthand knowledge of a creature, which rather reduces the utility, (though being taken on a tour of the "sky thrones" and meeting the undead squirrels sitting on each would itself, be hilarious). If you're OK with houserules, you can probably assert that each squirrel's truename can count as firsthand knowledge of them for purposes of circle dance. Then it's merely a matter of referencing the appropriate truenames of the beacons, and finding where the vectors intersect. But that's much less cool.

...

Or they can just cast find the path (or Knowledge(Geography) perhaps boosted to absurd levels with divine insight or improvisation) to get there and if visibility prevents landing due to some obscure house-rule, use dispel fog to clear a lane to your landing area and blindsight and/or true seeing and/or short range teleportation and/or feather fall to deal with any traps or concerns at the landing pad.

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  • \$\begingroup\$ Preexisting settlements can cause a lot of interference if you are using this method. For instance, it probably doesn't work at all near or inside a metropolis. \$\endgroup\$ – Martin Epsz Feb 3 '15 at 11:24
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    \$\begingroup\$ Surely if you're inside a metropolis you can just ask someone where you are? \$\endgroup\$ – Racheet Feb 3 '15 at 12:17
  • \$\begingroup\$ @Racheet: not if you are 5000' above said metropolis and trying to get down to it through solid clouds down to 500' AGL and blowing snow that limits visibility to a quarter-mile! \$\endgroup\$ – Shalvenay Feb 4 '15 at 0:15
  • \$\begingroup\$ OTOH: fantastic answer overall -- If Locate City's accurate enough to substitute for a VOR/DME parked in the town square, that puts me 95% of the way to a working IFR navigation infrastructure without any extra work on the ground! \$\endgroup\$ – Shalvenay Feb 4 '15 at 0:24
  • \$\begingroup\$ @Shalvenay I'm trying to work out a total cost of ownership for these systems. How many end-users of the systems will there be? \$\endgroup\$ – Brian Ballsun-Stanton Feb 4 '15 at 0:32
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If your goal is to make the equivalent of a GPS system (and if you can be flexible about the "some means other than sight" criterion), I think Permanent Image is probably the least awkward solution. http://www.d20srd.org/srd/spells/permanentImage.htm

Fly a few thousand feet up and create a giant image of some sort of crest, like the coat of arms of the local ruling family. Do this over any important landmark that people would want to travel to, using a unique crest for each one. The cost is very cheap (100gp per 20-foot cube plus some ten-foot cubes), so if desired you could cast several Permanent Image spells to make the image very large.

It's not completely clear from the spell description, but I believe these images could also be glowing so that they would be visible at night.

If eleventh-level spellcasters are not available, I believe you could use Illusory Wall to accomplish a similar (but less pretty) effect. http://www.d20srd.org/srd/spells/illusoryWall.htm

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  • \$\begingroup\$ Alternate answer, not relying on sight: use permanency and ghost sound several times to create a very loud ongoing sound, at a frequency undetectable by human ears. To find the beacon, cast speak with animals followed by summon monster I to summon a celestial dog and ask it where the noise is coming from. The major drawback to this method is that it will drive away any animal with hearing in that range, which could have environmental consequences. \$\endgroup\$ – Dan B Feb 3 '15 at 19:40
  • \$\begingroup\$ Nice... and much more elegant than my thought of an undead or warforged making absurdly high spires by playing a lyre of building. \$\endgroup\$ – Hey I Can Chan Feb 3 '15 at 21:58
  • \$\begingroup\$ @DanB -- unfortunately, I cannot be flexible in the "some means other than sight" criterion -- ever looked out the window of an airplane flying in solid cloud? Your alternate answer has promise, though...perhaps you could scrap your existing answer and replace it with your alternative? \$\endgroup\$ – Shalvenay Feb 4 '15 at 0:13
  • \$\begingroup\$ If all you want is to travel between cities, you should just use Locate City. :) However it may be worth noting that a large city might have a spellcaster who can cast Control Weather every day, so clouds might not be an issue. \$\endgroup\$ – Dan B Feb 4 '15 at 8:56
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You could mock this up with a customized version of Locate Object (senses the nearest beacon, range: 1 mile per level), along with a network of beacons (statues of the travel deity for the setting, with permanent Dancing Lights cast on them to give a visible beacon - see this OOTS comic for a nice example)

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