OpenSeaMap and Garmin nautical chart plotter

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on Garmin GPSmap 526

OpenSeaMap works on built-in Garmin Chartplotters of the GPSMAP series and on actual handhelds.


Revier gmapsupp.img for SD-card PC-Version for MapSource Update Comments
Europe Central (Next Generation) Download gmapsupp.img Download MS-Version twice per month
Europe Central Download gmapsupp.img Download MS-Version outdated version
Europe North Download gmapsupp.img Download MS-Version outdated version
Europe South Download gmapsupp.img Download MS-Version outdated version
America Central Download gmapsupp.img Download MS-Version outdated version
America Northeast Download gmapsupp.img Download MS-Version outdated version
America Northwest Download gmapsupp.img Download MS-Version outdated version
America Southeast Download gmapsupp.img Download MS-Version outdated version
America Southwest Download gmapsupp.img Download MS-Version outdated version
Red Sea and Indic Download gmapsupp.img Download MS-Version outdated version
Japan and China Download gmapsupp.img Download MS-Version outdated version
Indonesia Download gmapsupp.img Download MS-Version outdated version
Australia Download gmapsupp.img Download MS-Version outdated version
Arctic Download gmapsupp.img Download MS-Version outdated version


  1. Download the Zip-file.
    With 16 MBit about 30 minutes.
  2. Unpack archive (7Zip may cause problems).
  3. Install map:
    for SD-Card: copy 'gmapsupp.img' to the folder 'garmin' on your SD card.
    MapSource-Version: in folder 'openseamap' execute "install.bat" (MapSource or BaseCamp has to be installed before).



North Europe
Central Europe
South Europe, Mediterranean


America North, West Coast
Central Amerika, Caribbean
America North, East Coast
File:Osm america southwest.JPG
America South, West Coast
File:Osm america southeast.JPG
America South, East Coast


Red Sea, Indic

Characteristics of the map

When zooming in, you can see buildings.
When zooming out, the streets disappear and you will see an overview map of rivers and water surfaces.

Garmin GPSMap 526
Piloting chart
Garmin GPSMap 526
Harbour plan
Garmin GPSMap 526
Overview map

Tips & Tricks

  • Older devices may only support maps up to 2 GB. Use Mapsource version and upload a smaller part of the map in this case.
    Mapsource Europe (2012)
  • In case that some card tiles are not displayed on the GPS device, i. e. there are gaps, you should download a smaller map section onto the device using the MapSource version. This issue can happen on many Garmin devices if the downloaded map is too big.
  • New Colorado, Oregon and Dakota devices works well.
  • Older devices, equipped with the latest firmware-release, are even able to show scanning-pattern-charts. In the online-fullscreen-chart: choose menu "Tools > download chart". The file-format of these charts has to be KMZ. By the scanning-pattern-format all OpenSeaMap-sea-marks are displayed the same way as in the online-view. There has to be only one single KMZ-file in the directory CustomMaps on the Garmin device. Nevertheless you can use several KMZ-files, if you save them in other directories and move one for the time being, if needed, to \Garmin\CustomMaps\.


  • Next generation of map now online.
  • Many iENC features are now shown on the map.
  • Automatic update works again (thanks to new server).
  • Charts now as PC-version for MapSource.
  • Map updates are generated automatically.
  • A new server makes it possible to keep more maps up to date.
  • Groynes are displayed.
  • Built-up areas can be allocated to the Garmin MarineType "land urban" and will be displayed in different colours.
  • When zooming out, water surfaces and rivers will be displayed as before while streets move to the background.
Limitations and known issues
  • You cannot set the zoom level at which points of interest (POI) are displayed on newer marine devices. The map was therefore limited to POIs that are worth looking at from a nautical point of view in order to prevent the map from being too detailed.
  • Labelling of polygons (e. g. sports fields) is displayed too prominently on marine chartplotters. As this cannot be corrected, the labels of most of the objects are simply hidden.

Device list

Oregon 450

OpenSeaMap works on the following Garmin devices:
OK = tested successfully

All these devices should work for OpenSeaMap, also all the hand-helds and chart plotters in this list:

ok Type Comments
OK Echomap 50 s Plotter with integrated Fishfinder
OK GPSmap 7015
OK GPSmap 7012
OK GPSmap 6012
OK GPSmap 6008
OK GPSmap 6012
OK GPSmap 6008
OK GPSmap 5015
OK GPSmap 5012
OK GPSmap 5008
OK GPSmap 4012
OK GPSmap 4010
OK GPSmap 4008
OK GPSmap 720 / 720s Touch screen
OK GPSmap 620 Portable two-in-one touch screen device for street and marine applications
OK GPSmap 531 / 531s
OK GPSmap 527
OK GPSmap 526 / 526s
OK GPSmap 521 / 521s
OK GPSmap 421 / 421s
OK GPSmap 172C No longer available
GPSmap 60 cx Outdoor
OK GPSmap 60 CSx Outdoor
GPSmap 62 s Outdoor
GPSmap 62 sc Outdoor
OK GPSmap 62 st Outdoor
GPSmap 62 stc Outdoor
OK Colorado No longer available
OK Dacota 20 Outdoor
OK eTrex 10 Outdoor, by Mapsource + Multistorage (only 12MB)
eTrex 20 Outdoor
OK eTrex 30 Outdoor
eTrex Legend HCx Outdoor
OK eTrex Venture HC Outdoor, by Mapsource
OK eTrex Vista HCx Outdoor
Montana 600 Outdoor
Montana 650 Outdoor
Montana 650 t Outdoor
OK Oregon 550 Outdoor
OK Oregon 450 Outdoor with marine mode

Technical background

Over time, the various Garmin devices for car, outdoor and marine applications have evolved in different directions.

New maps are only compatible with the device for the respective target group. NT maps with lane assist guides and traffic information only work on Garmin nüvi devices, whereas the very detailed and colourful topographic maps are meant for use in outdoor devices. However, Bluechart G2 Vision only works in combination with marine devices. All sea maps, either traditional Bluechart, G2 or G2 Vision, work without TYPE files, as these do not display particularly detailed or multi-coloured images on shore. The Bluechart version does not offer green meadows, brown fields or even tree symbols in a forest. However, outdoor devices were designed to be used in a car or on a boat as well. For this reason, a partial support for NT and Bluechart (G2) was implemented. Unfortunately, they did not implement lane assist guides or Bluechart Vision.

So far, Garmin marine devices do not support TYPE files (for freely definable symbols, colours and textures). In order to display polygons, only a few clearly defined colours and textures are available. Without TYPE files, however, the priority of polygons cannot be defined. Maps that are displayed perfectly on Garmin outdoor or travel devices generally do have the same quality on marine devices and are therefore unusable.

Garmin has built in a locking mechanism in newer marine devices to prevent older Bluecharts (without G2) from being used (Message: "Karte nicht kompatibel" [Map is not compatible]). This lock also takes effect when OSM cards are involved.

Thus, a special OpenSeaMap chart was developed for owners of Garmin marine devices. It is particularly designed to adapt to the options of marine devices, which are rather limited compared to those of outdoor devices. This chart also works on outdoor devices with marine mode (e. g. Oregon) without any restrictions. It should also work for older marine devices. However, you should not download the entire map of Europa to less powerful devices in one go, but choose MapSource sections instead. Otherwise the image buildup will be very slow and there can be gaps in the map if the working memory is too small.

On devices that are exclusively used in cars (nüvi series) the map will probably not work without restrictions. Devices for aviation have not been tested so far.