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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.

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Table of Contents

By topic / company:

By filename extension:

Navigation: DrDepth

all DrDepth file types

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.

PDF Download File Format Documentation (last change: 2021-06-06)

Navigation: Johnson Outdoors (Brands: Humminbird, ...)

AutoChart file type

File format of the Humminbird LakeMaster AutoChart PC program

Filename extensions: *.ACD
File format of the Humminbird LakeMaster AutoChart PC program.

PDF Download File Format Documentation (last change: 2022-06-25)

Navigation: Garmin

Apollo aviation database

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.

PDF Download File Format Documentation (last change: 2022-06-04)

firmware

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.

PDF Download File Format Documentation (last change: 2022-05-01)

firmware

Firmware Update

Filename extensions: *.GCD
Firmware update file for Garmin outdoor GPS devices.

PDF Download File Format Documentation (last change: 2022-05-01)

firmware

Firmware Update

Filename extensions: *.GCX
Firmware update file for Garmin Aviation G5 device.

PDF Download File Format Documentation (last change: 2022-03-04)

points of interest

Points of Interest

Filename extensions: *.GPI
Garmin Points of Interest file format.

PDF Download File Format Documentation (last change: 2020-06-15)

container

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.

PDF Download File Format Documentation (last change: 2021-12-02)

map

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:

PDF Download File Format Documentation (last change: 2022-05-17)

user data

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:

PDF Download File Format Documentation (last change: 2021-11-01)

index

Map Index

Filename extensions: *.MDX
Garmin map index file for use with MapSource and BaseCamp.

PDF Download File Format Documentation (last change: 2021-07-04)

mapsource

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.

PDF Download File Format Documentation (last change: 2021-11-29)

firmware

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.

PDF Download File Format Documentation (last change: 2022-03-03)

recorded sonar

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.

PDF Download File Format Documentation (last change: 2022-02-17)

topographic database

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).

PDF Download File Format Documentation (last change: 2021-11-27)

Navigation: Navico (Brands: Lowrance, Simrad, B&G)

map

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).

PDF Download File Format Documentation (last change: 2021-11-07)

shapefile

Shapefile

Filename extensions: *.LSF
Navico (Lowrance) Shapefile. Contains attributed vector data.

PDF Download File Format Documentation (last change: 2021-10-24)

map creator

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.

PDF Download File Format Documentation (last change: 2021-11-01)

sonar log

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).

PDF Download File Format Documentation (last change: 2021-06-02)

help

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)

video recording

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".

PDF Download File Format Documentation (last change: 2018-01-01)


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Author: Herbert Oppmann (email address) updated: 2022-11-12