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Pre-load offline maps before you leave Wi-Fi or cell coverage

A lot of the best high-power launch sites share a feature: no cell coverage. A dry lake bed, a remote BLM field, a farm pasture an hour past the last tower. Apple Maps wants a network to stream tiles, and when the network is gone so is your map — unless you have already pulled the tiles you need onto the phone. AltosUI lets you do that at home over Wi-Fi (the usual case) or over cell on the way out if Wi-Fi isn’t available — whatever gets the tiles cached before you leave network coverage behind.

Why offline maps matter at the field

The Map tab plots your rocket's GPS track on an Apple Maps basemap. The Recovery Map on the Recover tab is your walking map when it is time to go pick the rocket up. Both of those rely on map tiles, and both will feel very different at a cell-dead site if you did not prepare.

With tiles cached on the phone, the Map and Recovery Map use them transparently. You open the tab, you see the map, and the network's absence does not matter. Without cached tiles, you see the basemap degrade to whatever iOS has already held in its own short-term cache — usually not enough.

What AltosUI downloads

The offline-map downloader pulls Apple Maps tiles to the app's on-device cache. You choose the region, the zoom range, and the map type — the app handles the tile math and the transfer. Everything that ends up on the device also shows up as an on-disk size so you can manage storage honestly.

Configuring a download

The download UI takes a handful of inputs. Set them once for a site you fly regularly and the job becomes quick.

  • Location — pick a known launch site from the catalog, or enter manual coordinates if your field is not in the catalog yet. The launch-site overlay catalog is the same list you see as shaded circles on the map.
  • Zoom range — how far in you want to be able to pinch. Higher zoom means more detail and more tiles. Wider range means more storage.
  • Radius — how far out from the center point you want coverage. A few kilometers is usually plenty for a typical club field; high-power sites with long drift may want more.
  • Map type — Road, Hybrid, or Satellite. Pick whichever matches what you use in flight; if you are unsure, Hybrid or Satellite tends to be more useful at rural sites where there are not many roads to label.
  • Walking Tiles — an option that fills in the higher-zoom tiles you will need on foot during recovery. This is the one you want enabled for the Recovery Map to look right at close range.

Downloads show live progress as they run and the current on-disk cache size as it grows. Nothing is hidden — you see exactly how much storage you are committing before you commit it.

A practical order of operations

  1. The night before the launch, on your home wifi, open AltosUI's offline-maps settings.
  2. Pick the launch site from the catalog if it is listed; otherwise enter the coordinates of the pad area.
  3. Set the zoom range and radius to cover the pad area plus a generous buffer for recovery.
  4. Turn on Walking Tiles so the Recovery Map has the close-in detail you will need on foot.
  5. Pick the map type you fly with, start the download, and leave the phone on wifi until it finishes.

When you arrive at the field, everything is already on the device. The Map and Recovery Map just work — you do not need to remember to flip anything on. The app uses cached tiles when the network is gone and online tiles when it is not.

Managing what is on the device

Over a season you will collect caches for a handful of sites. AltosUI lets you delete individual caches or clear the whole set — useful if you switch between home fields and a distant event field, or if you are just getting tight on storage. The on-disk size is visible so you know what you are giving back.

If you only fly at one field, you can cache it once and forget about it. If you fly at several, most people cache the current season's sites and drop the ones they are not using.

The desert-site workflow

The scenario this feature is built for: a Saturday morning drive to a dry lake bed, the last cell tower disappearing somewhere after the gas station, and a rocket due up in three hours. Without pre-loaded tiles, the Map tab is a blue dot on a blank basemap and the Recovery Map is no better — you are navigating by compass bearing and distance alone, which works, but is not the experience AltosUI was designed to give you.

With pre-loaded tiles, the blue dot lands on real terrain. Fence lines, washes, road networks, and the edge of the lake bed are all visible. When the rocket lands and you switch the Recover tab to Map mode, the route line between you and the rocket overlays real ground features. That changes what recovery feels like at a cell-dead site — from counting paces toward a number, to walking across a recognizable landscape.

Pairs well with

Offline maps work together with two other features that are easy to overlook before you need them:

  • The launch-site overlay catalog shows shaded circles for known club fields worldwide. If your site is in the catalog, it is one tap to select it for the offline download.
  • The AR Recovery HUD and Recovery Map both benefit from Walking Tiles being enabled — the close-in detail is what makes a walking map feel like a walking map rather than a pinpoint on a satellite photo.

What this is not

Offline maps are a basemap cache, not a GPS substitute. Your phone still needs its own GPS fix to know where you are, and your flight computer still needs its GPS fix to know where the rocket is. Cached tiles only solve the problem of the map disappearing — they do not solve the problem of a position disappearing. For how the app represents GPS accuracy on screen, see GPS uncertainty circle explained.

If a site you fly regularly is not in the catalog, the launch-site catalog guide covers how to request an addition. In the meantime, manual coordinates work fine — the download does not care whether the center point came from the catalog or from you typing it in.