Description Economy: Overland Adventures

Similar to floor plans in dungeons, overland maps enable description economy for overland travel and the world at large. They use the same elements -- map, key, encounter table, on a larger scale. 

The map

The overland map shows terrain (plains, forests, deserts, swamps, lakes, hills, mountains, oceans), routes (roads, passes, rivers, fords and bridges, coasts), settlements (towns, villages), and points of interest (castles, towers, keeps, ruins, dungeons, caves, landmarks, stone circles and unnatural effects), and the scael. It also can show borders or areas of control or roaming grounds for major factions. Together with a random encounter table, this is an economic way to describe the land. 

Put as much enriching detail as you can right on the map: evokative names of forests, towns and rivers, and the random encounter table. You can use colors to layer more information. A brief key can detail points of interest with one or a couple of lines of text on one page, or you can put that right on the map. For detail on specific points of intrest, dive down with a separate dungeon or town map.

You even can provide your players with a map handout, thereby giving the information to help them think what adventures might be of interest to explore. Here is an example of a map for the DM, and the corresponding one for the players.

Scale of the map 

For overland travel, traditionally hex grids are used, as you can move in any direction, and avoid the weird distance distortion effects from moving on square grids in steps, but it does not really matter. Your players do not even need to know what you use, and you just can measure distances directly, as you only need to be able to determine what is in a given area for random encounters and travel speed.

For a world map, a scale of about 24 miles per grid unit, equiavalent to one day of travel works well. Such a map will only show important cities, not minor towns or villages. It will cover a small continent, and allow for weeks of travel between faraway places. The Darlene map for Greyhawk uses 30 mile hexes, but it does not say so on the map, so I simplified to 24 miles or one day of normal travel per hex for my home game. 

For a region map, a scale of about 24 miles to an inch works well In Germany, we use centimeters, so on square graph paper, 5 miles per square of 0.5 cm is about 25 miles per inch. That covers about seven by eleven days of travel. While this still may not show individual homesteads, it will show small towns and large villages. The OD&D rules used 5 mile hexes, with a speed for foot travel of 3 hexes per day, mounted travel of about 6 in clear terrain, giving a similar size (and ruled that each hex would contain 2-8 villages of 100-400 inhabitants, so these small villages would not be on a map.)

Here are example region maps from my old campaign using the Darlene world map, for the Wild Coast, the Amedio Jungle, and the Bright Desert. These do not match the official canon, other than honoring settlements and terrain from the Darlene map. I ad-libbed towns and villages, and plugged in sites from Dungeon magazine adventures complete with the adventure to flesh them out. I used separate one-page dungeons for things like magic towers, or for the main towns on the map. 

Stocking the map

Like with dungeon floor plans, for overland adventures the map provides a meaningful framework, with points of interest that are complemented and fleshed out by random encounters, and natural structures in the form of roads and terrain.

You can think about this as you do about dungeon stocking: first you draw a map, then determine the factions, and place designed sites and areas on that map, for example dungeons, major towns, important castles and faction headquarters, the dragon's lair. For the rest, use a procedural approach to either pre-stock it, or even better, to generate it on the fly. 

Procedurally generated content or ad-hoc improvisation adds variation, and in combination with creative imagination to make it fit in, creates a richer world. If you do it on the fly, it frees you from wasting hours to pre-describe every area on the map, most of which will never be visited. 

You design a few procedures to generate castles and encounters that can be re-used over and over again, and create different experiences. Only who or what is it, and how many must be worked out by you, the rest can be covered by general rules of encounter distance, surprise and attitude, by combinatorics: is the encounter hostile or friendly, who is surprised, do you see them from afar or stumble upon them, are they out and about or in their lair, will they pursue?  

If your encounter tables include static items like homesteads, or villages, or if creatures are encountered in lair, the characters obviously cannot encounter them if they are not moving (e.g. at night, camping). In such cases, you must decide or predefine, if you just ignore the encounter, replace it with a re-roll or the next one in the list, or if you create a wandering encounter from it (e.g. the woodsman is not in his hut but out and about, because his son has vanished, and he is desperately searching for him. The hut is somewhere nearby).  

Encounters so created will also establish permanent finer details for your map, for example if you roll for a cottage, village,  keep or lair. And the players will never know.  

In Gygax' OD&D Greyhawk campaign, all he had was hex-grid wilderness map (he used the one from "Outdoor survival" that indicated sites for castles, roads, rivers, and terrain). Scale was three hexes per day on foot (so about 8 miles per hex), and the players would explore it hex by hex, the so-called "hexcrawl" (as opposed to "dungeon crawl"). All the content was or made up either "from whole cloth" on the spot or procedurally generated. OD&D included rules for all of this, getting lost and by random encoutner probabilities and tables for each territory type, with special rules for generating castles (which could be ruled by a wizard - so essentially wizard towers, or by a priest, so essentially temples).

Encounter cadence

You either will be checking a given number of times per day for encounters, or whenever the characters enter a new area (hex, map square) - in the latter case, the scale and size of your grid matters. 

Typical schemes are one per day, twice (day, night), trice (day, night, dawn/dusk), four (day, night, dawn, dusk), or six times per day (dawn, morning, afternoon, dusk, night, small hours). Encounter probabilities are typically 1 in 6, although more "dangerous" terrain often has higher probabilities (2 in 6 for forests, hills, deserts, 3 in 6 for swamps and mountains). Along travel routes the chance is also higher - albeit more likely with harmless merchants or ruling military than with monsters. 

Encounter Tables

The simplest approach is to not develop a specific table and just use a generic one by terrain, for example from appendix B of the 5e DMG (or from the older editions, use 1e if you prefer, or the OD&D tables). 

A more flavorful way is to create an encounter table specific to your map, to reflect what lives there. Your map will likely cover different terrain types, and you may want the pips for different creatures to differ between them, or maybe between day and night in the cursed woods (e.g. forest creatures by day, shadows by night). 

Yet another approach define who dwells or has their territroy in an area on the map, and if an encounter is indicated, that is what is encountered. For example in the woods described above, if you are in the fairy section, you could encounter pixies that will prank you with illusions, while in the warg reaches, you would encounter a pack of wargs instead. (Yeah "worgs", we all know it's wargs).

You can also overlay a general encounter table with specifics. Simply use a table with some pips for general encounters, say on a roll of 1-6 on d10, that is shared. On  a roll of 7-10 you instead encounter the area's special creatures.