Field manual · 02/17

Maps & Overlays

The Map Type button is the map sheet: which base map you are on, what is stacked over it, which of your own maps are loaded, what is downloaded for offline use, and the presets that restore a whole setup in one tap.

base maps

Twenty base maps, grouped in the Map Type sheet as Apple Maps, Google Maps, Mapbox, OSM-based, USGS and Custom Maps — plus the offline-only Satellite (Esri) you pick when downloading a region. They render on four engines — MapKit, MapLibre, Google and Mapbox — and your grid, pins and tools look the same on all of them.

Base map	Notes	3D	Contours
Apple Maps
Standard	Road map	✓	—
Satellite	Imagery	✓	—
Hybrid	Imagery with labels	✓	—
Satellite Flyover	Permanently 3D	always	—
Hybrid Flyover	Permanently 3D, labelled	always	—
Google Maps
Google Standard / Satellite / Hybrid / Terrain	No scale bar, no PDF printing	—	—
Mapbox — Pro, online only
Mapbox Standard	Vector map with 3D terrain and buildings	✓	—
Mapbox Satellite	Imagery draped over 3D terrain	✓	—
Mapbox Outdoors	Topographic, over 3D terrain	✓	✓
Mapbox Streets	Street map over 3D terrain	✓	—
OSM-based
OpenStreetMap	The standard OSM raster map	—	—
OpenTopoMap	Topographic, contours printed into the tiles	—	✓
Carto Topo Map	Vector topo map with live hillshade	—	✓
USGS (United States)
USGS Topo	The National Map topographic series	—	—
USGS Imagery	Aerial imagery with topographic detail	—	—
USGS Hydro	Hydrography	—	—
Custom
Custom Map	Your own XYZ source, MBTiles or imported raster	—	—

The Map Type sheet showing the Presets and Map Overlays sections above the base map groups — Map Type sheet

Mapbox — the 3D engine PRO

The Mapbox group adds a fourth rendering engine built for relief. All four styles drape over real elevation so a tilt shows the actual shape of the ground, and Mapbox Standard adds extruded 3D buildings. It is a Pro, online-only engine — the styles stream from Mapbox and are not part of an offline pack.

The grid overlay works on every base map, on all four rendering engines. Switching between Apple, Google, OpenStreetMap and Mapbox does not cost you your MGRS grid.

Live contour lines are a separate tool and draw over any base map, satellite included — see Terrain Analysis. The Contours column above marks only the maps that ship with contours already printed on them.

3D tilts the map into real terrain and buildings, and the button is offered on Apple Standard, Satellite and Hybrid and on every Mapbox map — the maps where tilting shows actual 3D content. The Apple Flyover types are that mode permanently. Every other map hides the button rather than offering a tilt with nothing to see.

map overlays

Map Type → Map Overlays → Add Overlay builds an ordered stack of raster layers drawn over the base map. This is map imagery — trails, pistes, sea marks, your own tiles — and is not the same thing as the layers that hold your saved items.

Built-in overlays PRO

Ready-made layers from OpenStreetMap, drawn over any base map: Hiking Trails (waymarked hiking routes and footpaths), Ski Trails (ski pistes and marked ski routes), Cycling Trails (signposted cycling route networks) and Sea Marks (buoys, beacons and navigation marks).

Your custom maps

Any raster source you added yourself in Map Type can be stacked as an overlay too — an imported GeoTIFF over satellite imagery, for example.

Each entry in the stack has its own controls:

Opacity: 20 % to 100 %
Brightness: −100 % to +100 %
Contrast: −100 % to +100 %
Saturation: −100 % to +100 %, where −100 % is greyscale
Hue: 0° to 360°, in 5° steps
Invert Colors: Flips the tile — turns a white-background topo sheet dark
Erase Color: Makes one colour transparent so the map underneath shows through — White, Black or a colour you pick, with a Tolerance slider. The quick way to drop the paper background out of a scanned sheet or a GeoPackage's white fill.
Move Up / Down: Reorders the stack
Show / Hide: The eye, without removing the entry
Reset: Returns opacity and every adjustment to default
Remove: Takes the layer out of the stack

Basemap Adjustments applies the same sliders to the base map itself. Drop the saturation and raise the contrast under a coloured overlay and the overlay reads clearly.

Built-in overlays stop at zoom 18. Past that the tiles are magnified rather than refined — the data simply does not go deeper.

Built-in overlays are not part of an offline pack unless Include Map Layers was switched on when the pack was created. On a downloaded region they otherwise appear only while you have signal.

your own maps PRO

Map Type → Custom Maps → Add Custom Map loads a map the app does not ship.

Name: Required — how it appears in the map list
Source Type: An online tile service, or a file on the device
URL Template: An XYZ or TMS template
MBTiles File: Import MBTiles File from Files, or Download MBTiles from URL
Max Zoom: How deep the source goes
Tile Size: 256 or 512 pixel tiles

Import a scanned or georeferenced map

Map Type also imports GeoTIFF, GeoPDF and AlpineQuest .aqm files. The app reads the file's coordinate system, ground resolution and zoom range, converts it into a tile pyramid, then reports that it was added to Custom Maps and is now the active map — or tap Add as Overlay Instead to stack it over the base map you are on rather than replacing it.

Open a map file from another app. Send a .tif, GeoPDF, .aqm, .gpkg or .mbtiles into Tactical GPS from Files, Mail or any share sheet and it goes straight into Custom Maps. A raster MBTiles asks first: Use as Base Map or Add as Overlay Layer; a vector MBTiles is used as the base map directly.

A GeoPackage can also carry map tiles, features and elevation coverage at once — import it from Settings and it contributes to all three. See Import, Export & Backup.

image overlays PRO

An image overlay pins a flat picture to the map — a hand-drawn sketch map, a scan without a coordinate system, an operation graphic — and stretches it to fit the ground.

Open Map Type → Image Overlays → Add Image from Photos and pick a picture.
You drop into placement: drag and pinch the image until it sits over the right ground.
The overlay joins the list with its own Opacity slider (10 % to 100 %), a Reposition button to place it again, and Delete.

Unlike a GeoTIFF, an image overlay carries no georeference of its own — you place it by eye, so it is the tool for artwork and sketches rather than survey-grade raster. It is also listed in the Loaded Maps panel for quick opacity and show/hide.

the loaded maps panel

Once anything is stacked on the map — overlays, image overlays, several item layers — a Loaded Maps button appears in the control column with a count badge. It opens a panel that puts the whole stack in one place without going back into the Map Type sheet.

Basemap: Shows the current base map; tap to open Map Type
Map Overlays: Touch-and-hold to drag an overlay up or down the stack, each with an opacity slider (20 % to 100 %) and an eye PRO
Image Overlays: Opacity and show/hide for each placed picture
Item Layers: Your saved-item layers, each with an opacity slider, an eye and an Active badge on the editable one

Reordering overlays and changing a layer's opacity are Pro; seeing the stack and toggling an eye are free. Manage Layers… at the foot jumps to the full layer list.

the location button

The location button in the control column cycles three states, so one control both centres the map and chooses how it tracks you:

Off: The map stays where you put it. The button is white.
Follow: The map keeps your position centred as you move. The button turns green.
Heading Up: The map centres on you and rotates to the way you are facing, so the map matches the ground in front of you.

Tap again from Heading Up to return to Off. The states read out as Off, Follow Position and Heading Up for VoiceOver.

offline maps PRO

Two things work offline, and they are different. Caching is automatic: every tile you look at is kept, so ground you have already scrolled over stays available with no signal. An offline region is deliberate: you box an area and download it whole, in advance.

Position and zoom the map over the area you want. The box follows the screen.
Open Map Type → Offline Maps → Add Offline Region.
Give it a Region Name — this is required.
Pick the base map to bake into the pack. This is also where Satellite (Esri) lives — a high-resolution imagery layer offered only here, for offline use.
Decide whether to Include Map Layers (the overlay stack) and Include Terrain Data (elevation for contours and analysis).
Check the estimate — the panel shows roughly how many tiles and how many megabytes.
Download.

The panel says	Meaning
Zoom level OK	The area will download at a sensible size.
Large area – zoom in more	It will work, but expect a big download.
Area too large – zoom in	Refused. Box a smaller area.
Too many tiles – zoom in	Refused on tile count rather than area.

Packs download to zoom 14 — zoom 16 for the imagery base maps (USGS Imagery and Satellite (Esri)), which only gain detail from deeper tiles. There is no max-zoom choice; the depth is fixed and clamped to whatever the base map supports. Zoom 14 is roughly the detail of a 1:50 000 sheet; deeper zooms still work online and from the automatic cache.

Each downloaded region's row menu offers:

Refresh Tiles — discards and re-downloads the pack, for when the underlying map has been updated.

Export as MBTiles and Export as GeoPackage — hands the region to another application as a standard file. USGS base maps only: The National Map permits bulk download, and the other sources' licences and vector styles do not. Exports are capped at 20 000 tiles, trimming the deepest zooms first.

Settings → Map Cache → Auto-Refresh Offline Maps keeps packs current on its own: Never, Every 30 Days or Every 90 Days, checked at launch.

map presets PRO

A preset is a named snapshot of your whole map setup. Map Type → Presets → Save Current View stores it; tapping the row applies it.

A preset captures the base map, which custom source is active, the entire overlay stack with every per-layer adjustment, the basemap adjustments, whether the grid is on and its system, density and opacity, the dark-mode setting and the 3D setting.

Each preset's menu offers Update with Current View, Rename and Delete.

Build one preset per job — Navigation on hybrid with a fine grid, Terrain on Carto topo with contours and hillshade, Night with the base map darkened and everything desaturated — and switch in one tap instead of six.

A preset whose custom map source has since been deleted falls back to the Carto topo map, and one pointing at an unavailable Google base map falls back to Apple Standard. Stack layers whose source is gone are dropped silently rather than breaking the preset. Presets are included in a backup archive and merge by identity on restore.

touch lock

The padlock in the control column freezes every map gesture — pan, zoom, rotate and tilt — on all four engines. The button turns red while locked, and the lock survives switching base maps.

For a phone on a vehicle mount, strapped to a forearm, or in a jacket pocket where a stray touch would otherwise lose your position on the map.

Unlocking restores rotation to whatever the compass button had it set to.

Add Lock Map as a quick-action chip and it becomes a one-tap toggle that reads Unlock while active.

the grid overlay

The grid button on the map shows and hides it; Settings → Grid controls how it looks. All four map engines draw it from the same source, so it registers identically on Apple, Google, MapLibre and Mapbox maps.

Grid Type: MGRS, UTM, Lat/Lon, CK-42, CK-42 X/Y or Custom
Grid Density: Coarse · 100 km, Standard · 10 km, Fine · 1 km, Ultra · 100 m
Colours: Three levels, named for the system in use
Line Thickness: ×0.5 to ×3, in 0.25 steps
Grid Opacity: 20 % to 100 %, in 5 % steps
Label switches: Turn the zone / square and the line-value labels on or off

The three colour rows are renamed to match the system: MGRS gives Zone (GZD), 100 km Grid and Fine Grid; UTM and the CK-42 grids give Zone Boundaries, Major Lines and Minor Lines; Lat/Lon gives Equator & Prime Meridian, Major Lines and Minor Lines.

The label switches follow the system too: MGRS has Zone & Square Labels and Grid Number Labels; UTM and CK-42 have Zone Labels and Line Value Labels; Lat/Lon has the line-value labels only.

Grid settings with the system, density, three colour rows and the opacity slider — Grid settings

CK-42 grids

CK-42 and CK-42 X/Y draw the Soviet Gauss-Krüger grid on Pulkovo 1942 — the one printed on Warsaw-Pact map series. The two differ only in axis order, matching the sheet or the receiver in front of you. These are grid overlays; the matching coordinate readout is a separate setting — see Coordinates.

Custom reference grid

Set Grid Type to Custom and Manage Custom Grids builds your own lettered-and-numbered grid: an origin and corner, cell width and height, a rotation, the number of columns and rows, and whether each axis is lettered or numbered (with an optional Skip I and O). Labels sit along the edges or in every cell. Up to 400 cells — a drop-zone grid, a sector overlay, a search-box reference of your own.

The grid is zoom-adaptive — it thins out as you zoom away so the map never disappears under lines.

map cache

Settings → Map Cache → Clear Cache shows how much space the automatic tile cache is using and empties it.

The size shown is net of your downloaded offline regions — it only promises space that clearing can actually free. Clearing the cache never deletes an offline region.

The Carto topo base map with live contour lines and hillshading — Topographic base map

Tiles from OpenStreetMap, OpenTopoMap and the trail overlays are cached as you zoom and scroll. Scrolling over your area of operations on wi-fi before you leave is a rough but effective substitute for a downloaded pack.

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