File Format Documentation
I have fun reverse engineering file formats and creating documentation for it. Here are some results of my work.
The documentation comes as a PDF (portable document format) file which describes the sections and fields that make up the file together with their purpose. It also contains a reference section which contains links to the used sources of information, to programs using this file format, and to places where sample files can be obtained.
Table of Contents
By topic / company:
By filename extension:
Navigation: DrDepth
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File formats of the DrDepth PC program |
Filename extensions: *.DDB, *.DDD, *.DMM, *.DNT, *.DRD, *.DWP
File formats of the DrDepth PC program that was later bought by Humminbird (more exactly: Johnson Outdoors Inc.), and replaced by LakeMaster AutoChart.
- DDB: Database
- DDD: Demo
- DMM: Mobile map
- DNT: Waypoint notes
- DRD: Data
- DWP: Waypoint data
Download File Format Documentation (last change: 2024-01-27)
Navigation: Johnson Outdoors (Brands: Humminbird, ...)
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File format of the Humminbird LakeMaster AutoChart PC program |
Navigation: Garmin
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Apollo Aviation Database |
Filename extensions: *.BIN
Aviation Database for Apollo GX device series (GX50, GX55, GX60, GX65 and 2101 GPS units). These devices were made by II Morrow, Inc. which was bought by UPS Aviation Technologies which was then bought by Garmin as Garmin AT. They are GPS receivers combined with a comm radio. The date base contains airports with their frequencies, runways and approaches, intersections, radio beacons, and special use airspaces.
Download File Format Documentation (last change: 2022-06-02)
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Firmware File |
Filename extensions: *.BIN
Single ARM firmware file for Garmin outdoor GPS devices. This type of firmware files is encountered only embedded in GCD and RGN firmware update files.
Download File Format Documentation (last change: 2024-03-17)
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Firmware Update |
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Firmware Update |
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Points of Interest |
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Image, UserData, and Text-to-speech Container |
Filename extensions: *.IMG and *.ADM
Garmin Image (IMG), UserData (ADM), and Text-to-speech (TTS) Container File Format.
This file format is used to combine a set of files into a single file. It is similar to a file system on a disk, but it lacks hierarchy. The contained files (called subfiles) form a flat list - there are no subdirectories.
This file format is used for image files (IMG) with filename extension *.img, for user data files (ADM) with filename extension *.adm, and for Text-to-speech data which usually appears in *.RGN files in region 17.
There are separate documents available here for the IMG and ADM subfiles.
Download File Format Documentation (last change: 2021-12-02)
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Map |
Filename extensions: *.DEM, *.GMP, *.IDX, ...
Garmin IMG map file for use in outdoor GPS devices.
Uses the IMG/ADM/TTS container file format (documentation also available here) to combine all the subfiles into a single file.
This document describes the file format of the following subfile types:
- DEM: Digital Elevation Model
- GMP: Subtile of a larger area
- IDX: ?
- LBL: Labels for map elements, city names, localities, etc.
- MAR: ? marine? (in bluechart 2 nautical charts)
- MD2: ?
- MDR: Binding individual map files together.
- MPS: Similar to the TDB file in that it is a list of maps along with other information describing the set.
- NET: Road network information (intersections, etc.)
- NOD: Routing information.
- QSI: ?
- RGN: Map elements such as polylines, polygons and points.
- S16: ?
- SNR: ?
- SRT: Lookup table for characters
- TRE: Map structure information that organizes the map elements into a data tree.
- TRF: ?
- TYP: Custom rendering styles. How a map element will be rendered on the GPS which allows you to display things in a different way.
Download File Format Documentation (last change: 2023-02-24)
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UserData |
Filename extensions: *.PRX, *.RTE, *.TRK and *.WPT
Garmin ADM file for storage of user data on marine GPS devices.
Uses the IMG/ADM/TTS container file format (documentation also available here) to combine all the subfiles into a single file.
This document describes the file format of the following subfile types:
- PRX: Proximity records
- RTE: Routes
- TRK: Tracks
- WPT: Waypoints
Download File Format Documentation (last change: 2023-01-27)
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Map Index |
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MapSource / BaseCamp |
Filename extensions: *.MPS, *.GDB and *.GFI
Files with filename extension *.mps are created by MapSource. Starting with version 6, MapSource introduced a slightly modified format using filename extension *.gdb. BaseCamp stores its user interface data in *.gfi format.
Download File Format Documentation (last change: 2024-02-04)
 |
Firmware Update |
Filename extensions: *.RGN
Firmware update file for Garmin outdoor GPS devices.
RGN probably stands for "region". Note that the RGN files contained in IMG files have a completely different structure and purpose.
Download File Format Documentation (last change: 2024-05-16)
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Recorded Sonar Data |
Filename extensions: *.RSD
These files are created by Garmin ECHOMAP and some GPSMAP devices, and can be opened and viewed with HomePort.
Download File Format Documentation (last change: 2024-03-19)
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Topographic Database |
Filename extensions: *.TDB
Topographic Database: The file that holds the information which *.img belong to the mapset. Mapset: An assortment of map tiles (*.img) that is joined together by .tdb, overview image (mapset00.img), and .mdx
(cited from here).
Download File Format Documentation (last change: 2021-11-27)
Navigation: Navico (Brands: Lowrance, Simrad, B&G)
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Atlas Type 5 |
Filename extensions: *.LCM and *.AT5
Navico map format.
The AT5 map format is a Lowrance map format supported by a wide range of Lowrance GPS devices [..]. The AT5 format is able to combine vector layers, such as contour lines, with raster (image) layers
(cited from here).
AT5-charts work with seachart-plotters from Lowrance, Simrad and B&G. It is also possible to use them with Insight Planner which is a tool for marine navigation
(cited from here).
Download File Format Documentation (last change: 2021-11-07)
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Shapefile |
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Map Creator Project |
Filename extensions: *.SAP
Navico Map Creator / Insight Map Creator Project File. Stores all program settings and the directories and file names of input and output files.
Download File Format Documentation (last change: 2021-11-01)
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Sonar Log |
Filename extensions: *.SLG, *.SL2 and *.SL3
Binary format used by Navico chart plotters to save tracks. *.slg is format 1 (sonar only), *.sl2 is format 2 ( sonar and structure) and *.sl3 is format 3 (includes ForwardScan).
Download File Format Documentation (last change: 2021-06-02)
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Information File |
Filename extensions: *.NIF
A Navico Information File (NIF) is created when you use menu entry Settings > System > About > Create report. The report is a comprehensive picture of everything connected to your system, its configuration, status and settings
(cited from here).
This file is just an archive in the
"tar" format which is then compressed with
gzip. To open the file and extract its contents on a Windows operating system, you can use the command line tools tar and gzip from the
Cygwin project, or you can use archivers like
7-Zip (use context menu entry 7-Zip > Open in Windows Explorer) or
WinRAR (rename *.nif to *.tar.gz first).
Other: Panasonic (Brands: Matsushita, Technics, JVC)
 |
HD Writer AE |
Filename extensions: *.CONT, *.IIS, *.PMPD and *.TMB
HD Writer AE is a program from Panasonic that comes with their Digital Video Cameras which use the AVCHD recording format.
A *.cont file describes the content of a scene or directory, an *.iis file contains data for the Intelligent Index System, an *.mtv file contains additional info for the MPEG2 video (*.m2ts), a *.tmb contains a thumbnail image, and an *.pmpd file contains "maker private data".
Download File Format Documentation (last change: 2024-01-27)
The icons on this page were taken from:

Author: Herbert Oppmann ( ) |
updated: 2024-05-24 |