How the map works

Taking the map offline

On this screen

Saves the area you are currently looking at as a named region. It records the bounding box, a zoom range and which basemap was showing — it does not fetch anything yet. Think of it as marking the ground you care about.

Map regions

The regions you have marked. Each one shows how much ground it covers, how many tiles that works out to at the zoom range you chose, and roughly how much space they will take. Widen or narrow the zoom range and the numbers move with it — a region at zoom 14 costs about sixteen times what the same region costs at zoom 12.

Download for offline

Fetches the tiles and keeps them on the device. It stores the basemap you have selected plus any layers switched on over it, and the panel names what it is about to store before you press it. A tile that has already been downloaded by an overlapping region is not fetched twice.

Two things it will tell you that it could have glossed over. If part of a region falls outside what the map covers, it says how much rather than counting it as saved — that is the sort of reassurance there is no way to check until there is no signal to check it with. And if you press Stop, it stops there and keeps what it already had.

Once a region is downloaded, the map draws from those tiles with no network at all. The figure under the region list is read from the browser rather than estimated, and is what decides whether the next download will fit.

What cannot be downloaded here, and why

Anything drawing from Mapbox cannot be stored offline by this app — Mapbox Outdoors, Satellite Streets, and Byways Topo when it is reading Mapbox geometry. Mapbox reserve offline storage to their own native mobile toolkit. This app is a web view, which is not that toolkit and has no offline facility at all — so it says so rather than offering a button that quietly downloads something else.

Worth being exact, because it affects what a paid tier could offer: Mapbox offline is a real capability, it is simply not available on the web. Their mobile toolkit downloads regions properly and is billed under their mobile pricing. Reaching it would mean the app drawing its maps natively on the phone rather than in a web view — a different piece of engineering, not a setting, and not something a paid plan alone unlocks.

Byways Topo drawing from our own archive can be. The archive is one file rather than a service, so a download reads the region out of it and keeps the pieces on the device — same regions, same counts, same progress line as any other download. It is what the second foundation below was for.

Everything else can too: USGS Topo and Imagery, the state aerial and lidar layers, BLM, the FAA layers and the rest. All of it is public data with no such condition attached.

The OpenStreetMap community tile servers are also left alone. Nothing forbids downloading from them, but their usage policy asks bulk downloaders to run their own servers, and filling a phone from a volunteer-funded service is what it asks people not to do.

Save as a picture

The one export that always works. It costs no tiles, needs no account and no network, and on a phone in a canyon it is often the whole answer. On a phone it offers Save to Files alongside Messages and AirDrop.

Why some maps download and some do not

There are two kinds of basemap here, and the difference decides what you can take with you.

Picture maps

USGS Topo, the aerial imagery, the state lidar hillshades. These arrive as finished pictures — the agency drew them, and the app places them. They are public data, they cost nothing to use, and they can be stored on your device. Everything you can download is one of these.

Drawn maps

Byways Topo is drawn in the browser: the palette, the road hierarchy, the route shields and the labels are all this app's, applied to raw geometry streamed in as you pan. That is why it looks the way it does and why it stays sharp when you rotate or zoom between levels.

Where that geometry comes from decides everything else. From Mapbox it has two consequences: viewing it uses a metered allowance, and Mapbox reserve offline storage of their data to their own native toolkit, which this app is not built on. So the best-looking map was the one you could not take out of signal — which is the wrong way round for a back-roads atlas, and is what the section below is about fixing.

The second foundation

The cartography is ours; only the geometry underneath is rented. So Byways Topo now knows how to draw from a second source: an OpenStreetMap-derived vector basemap we host ourselves, distributed as a single archive the browser reads a slice of at a time. Same drawing, different foundation — no metered allowance, and a map that is a file, which is what makes downloading a region a sentence that can mean something.

Two things came out better than expected. The road hierarchy survives intact — the eleven weights that let you read this map at speed, from interstate down to footpath. And the route shields stop guessing: Mapbox describes a marker's shape and leaves the question of who numbered the road to be worked out from wherever the map happens to be looking, which is wrong within a few miles of a state line. The new source names the network outright.

Some things are genuinely lost, and they are listed rather than absorbed. There are no contour lines and no hillshade in the new source — both are already available here as their own overlays. There is no surface field at all, so the dashed unpaved marking cannot be drawn from it, which is a real loss on a map that describes itself as tracks and surfaces. And nothing marks a road carrying two route numbers, so a doubled road gets one shield rather than two.

Mapbox stays available. The point of the change was never to leave it behind — it is that the default should not cost money to look at, or stop working where there is no signal.

Layers and what they mean

The map underneath, and the layers over it

One basemap is drawn at a time; layers stack over it, each with its own opacity. A layer switched on for one state stays on when you leave that state and comes back when you return — it is simply not drawn or listed while you are elsewhere.

Zoom floors

Some layers only load past a certain zoom, and say so with an amber zoom in to 10 badge rather than appearing broken. The floor is not fussiness: these services answer a fixed number of features per request, and a request covering too much ground comes back truncated. On a layer about where you may not fly a drone, a silently missing cell reads as open airspace, which is the wrong way to be wrong.

Where the data comes from

Every layer names its source in its own description. They are agency services read live, not copies — so a layer reflects what that agency publishes today, including its gaps.

The agency's own map is the authority. A published service can lag the map an agency prints, a gate can close the week after a dataset is refreshed, and a boundary drawn at one scale is not a survey. Use this to plan and to orient; check with the managing office before relying on it for access.

Not responding

A red badge means that layer's service is not answering. Some are known to be intermittent — the FAA's drone layers sit behind a request quota shared with every other consumer of that service, and it is regularly exceeded by people who are not us. The layer keeps whatever it last drew rather than blanking.

The drone layers

Nothing here is a flight authorisation. It is the FAA's own data drawn on a different map, and it can be out of date.

Drone ceilings

The UAS Facility Map: the grid LAANC reads when it approves a flight. The number is how high LAANC will grant that authorisation instantly — not a speed limit for the sky. Every cell on the grid is inside controlled airspace, and a Part 107 flight there needs authorisation whatever the cell says. A ceiling of 0 does not mean the airspace is closed; it means nothing is pre-approved and the request goes to further coordination or FAA DroneZone instead.

Outside controlled airspace there is no grid at all. That is Class G, where no authorisation is needed — an absent cell is an answer, not a gap.

Restrictions and advisories

Red is do-not-fly; amber is permitted with permission or with care. These are standing and scheduled restrictions only. Same-day temporary flight restrictions — wildfires, VIP movements — are NOTAMs, and they are not in this layer. The card links to the FAA's current list; check it before you fly.

Military operating areas are deliberately left out. They do not restrict civilian flight and are generally based well above where a drone flies, so drawing them would fill the screen with warnings that do not apply.

Directions and the trip planner

The trip planner works out how far apart your stops are, how many days that is, and where the days break. It will also draw the actual road route. What it will not do is give you turn-by-turn directions, and that is a decision rather than a gap — navigation is what Apple Maps, Google Maps and Waze are for, and they are better at it than anything this could become. So a stop is handed to whichever of those you already use.

Why a single stop offers three apps and a whole trip offers one

Because the three do not agree about what a link may carry, and only one of them takes more than one destination.

• Google Maps takes a start, an end, and up to nine stops in between. That is the whole trip, opened as a route you can then start.
• Apple Maps takes one destination. Its link format has no multi-stop form at all.
• Waze takes one destination, and answers a link carrying several with an error rather than quietly using the first.

So every waypoint and every tapped place offers all three, and Send to Google Maps on a trip offers one. If your trip has more stops than a Google link holds, the planner says exactly how many it is sending and how many it is leaving out — a trip that quietly loses its last four stops is something you discover in a car park.

Walk-in stops

A pin dropped at a waterfall is often not on a road. The router does not refuse it — it silently routes to the nearest road it can reach — so the planner measures the gap, draws it as a dashed line, and says how far it is on foot. That distance is deliberately left out of the driving time, because the car does not go there.

Accounts and your own files

Everything you save — folders, waypoints, notes, imported files — lives in your browser by default and needs no account. Signing in syncs those folders between devices; signing out leaves them on the device, because clearing them would look like data loss.

Exports are GPX by default, which is what Garmin, Gaia, AllTrails and every handheld will import. GeoJSON is offered alongside it for anything that wants the full properties.