What is the RTMAP file format?
An .rtmap file is a Tiled Raster Map in the proprietary CompeGPS / TwoNav format, developed by CompeGPS TEAM S.L. (now marketed under the TwoNav brand). The format stores georeferenced raster map imagery split into a grid of tiles, enabling GPS navigation software and devices to load and render only the map sections currently needed - reducing memory pressure and speeding up panning and zooming on resource-limited GPS hardware.
.rtmap files are binary and carry a CompeGPSRasterImage identifier string in the file header. They belong to a multi-file map package: a complete calibrated map typically includes companion files such as an .rmap index or a .imp calibration file that supply geographic coordinate data, scale, and projection parameters. The .rtmap itself holds the tile image data; without its companion files the tiles cannot be correctly placed on the earth's surface.
The format is read and created primarily by CompeGPS Land (now TwoNav Land) on Windows and macOS, and by the TwoNav GPS app on Android and iOS. It is also compatible with a range of dedicated TwoNav GPS receivers.
Because the format is proprietary and undocumented publicly, third-party GIS tools do not natively support .rtmap. Conversion to or from open raster formats generally requires TwoNav Land or another compatible CompeGPS tool.
Security & safety
RISK: LOWA .rtmap is map image data, not executable, so opening one in TwoNav software is safe. The only practical issue is incompleteness: a .rtmap separated from its .imp control file and sibling tiles may fail to display - that's a missing-files problem, not a security one. Buy/download maps from TwoNav or reputable map providers.
Format details
in a nutshellPrograms that open RTMAP files
Windows1 app
CompeGPS Land / TwoNav Land
Free Install TwoNav Land (formerly CompeGPS Land), then open the map; keep the .rtmap tiles and the .imp file together in one folder. 
macOS1 app
TwoNav Land (macOS)
Free Use the macOS build of TwoNav Land if available for your version; load the map folder containing the .rtmap + .imp set. 
Android1 app
TwoNav (GPS app)
Freemium Install the TwoNav app and copy/sync the map (all .rtmap tiles + .imp) into its maps folder to view it on the phone.
TwoNav (GPS app)
Freemium Install the TwoNav app and import the map through the app/TwoNav account to use it on iOS. Technical details
deep spec| File structure | Binary tiled raster image container; raster map data is partitioned into a regular grid of tiles for partial loading |
| Header identifier | `CompeGPSRasterImage` string reported at the start of the file header (no publicly confirmed fixed-offset magic bytes) |
| Tile organization | Each tile covers a fixed geographic bounding box; the grid layout enables selective loading during pan and zoom |
| Geographic referencing | Coordinate calibration and projection data are stored in companion files, not embedded in the `.rtmap` tile itself |
| Multi-file dependency | Requires companion calibration or index files (e.g. `.rmap`, `.imp`) to form a complete, georeferenced map package |
| Tile image encoding | Raster tiles typically encoded with JPEG or a similar compressed image format inside the binary container |
| Zoom-level handling | A full map set may span multiple `.rtmap` files at different resolution scales to support smooth zoom transitions |
| Supported projections | WGS-84 (GPS standard) is primary; additional projections depend on source map data and the companion calibration file |
| MIME type | `application/octet-stream` - no registered IANA media type exists for this format |
| Software ecosystem | CompeGPS Land / TwoNav Land (Windows, macOS desktop); TwoNav GPS app (Android, iOS mobile) |
| Hardware compatibility | Compatible with dedicated TwoNav and CompeGPS GPS receivers that support custom raster map loading |
| Third-party GIS support | No native support in mainstream GIS tools such as QGIS or OziExplorer; CompeGPS/TwoNav tooling required |
| Intended use case | Offline navigation raster maps for outdoor activities - hiking, cycling, marine, and aviation - on GPS devices |
| Related proprietary formats | `.rmap`, `.imp`, `.vmap`, `.cmap` - all part of the CompeGPS / TwoNav map file ecosystem |
| Released | CompeGPS Land/Air era (CompeGPS TEAM, now branded TwoNav) |
| Specification | www.twonav.com |
RTMAP conversions
Community Q&A
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