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Started by nik, December 09, 2011, 01:19:42 PM

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I am old and not tech savy-took four tries to log on.  I have a Garmin 76cx and wanted to down load NOAA raster charts.  Have easily downloaded and put on GPS GPSFILEDEPOT maps.  Try to follow instructions for down loading what is listed as free raster charts and does not make sense as they do not seem free.  Need, it seems to buy some software.  Am I missing something,  Is there a place to down load charts or should I spring for the Garmin blue charts


What exactly are you trying to download? Can you post a link?


Those are not in a format that will work directly with your GPS. Looks like Oz make some here using a program like MOAGU perhaps?

I suspect you will be better off purchasing Garmin's maps.


Thanks for the quick response.  I sea kayak in coastal waters so was looking for charts.  The 24000 maps are helpful with the overlay of trails as it has buoys but NOAA charts have more specific info such as depths and sand bars etc.  I guess I will bite the bullet but thank you for the responses.


The newer GPS units do a much better job with the raster maps.  MOAGU is the only option for true raster on the unit you own.
Dan Blomberg
Administrator - GPSFileDepot
GPS Units: Garmin Dakota 20, Garmin GPSMap 60csx, Nuvi 255W, Nuvi 250W, ForeRunner 110, Fenix 2, Tactix Bravo, Foretrex 401
See/Download My Maps!


For clean graphic raster maps, a raster-to-vector polygon converter is probably the best approach. Standard Moagu maps break a raster map down into points, not polygons - best quality, but unless the map is mostly white, very slow. BMap2MP will do this; command-line, but Moagu has a built-in GUI front-end that simplifies the project. Will take some significant work to get the best results; there's a tutorial at GPS File Depot that describes the process for a nautical chart.

MapWel will also do raster-to-vector conversions, quite nicely, and also let you create your own vector-based maps. Non-standard .img files make it more difficult to install in BaseCamp/MapSource for transfer to older Garmins; for newer Garmin models, you can just copy the .img file to your unit.


    Greetings all,

    (NOTE 2012feb09: please go to reply #14, I got it to work fairly well.  Neat product)

    I'd posted sometime earlier about using Moagu to load a NOAA chart into my little Rino 120.  Seemed to convert and load ok, but file did not appear in the GPS.  Since then, I purchased an Etrex Vista hxc.  For other non-tech-heads who wish to follow this path; it works. Sort of.  Here is a summary of converting NOAA chart 18532.

    The basic steps are;
    1. download or otherwise acquire the chart's georeferenced computer file
    2. convert it to Garmin's *.img format
    3. load it into the GPS

    Just three little steps.....

    NOAA charts download as *.kap files.  This chart consisted of  five *.kap files.  It took a bit of investigation to find the one for the neighboring stretch of the Columbia River.   Once determined, NOAA software, "NOAA Chart Reprojector," converts *.kap to TIFF graphic files, *.tif. Note that a second file extension *.tifw appears. This file contains the georeferencing information. It is essential. To make it digestible for Moagu, however, follow instructions and edit the extension to *.tfw. Oh, and check the image's pixel size. If too large, Moagu can not handle it. Why is that? As Dr. Who would say, "I will tell you later" (if I find out). To make smaller, see instructions on using "microdem" software.

    Then enter the land of Moagu.  Not all Garmin models are compatible but my new Etrex hcx is. Bring the *.tif and *.tfw files into Moagu, follow the directions closely and 30-40 minutes later..... To transfer the file to the etrex, I used "sendmap" software because the upload buttons on Moagu were inoperative.

    The steps are a bit convoluted. It took the vintage 1946 Tenessee processor in my shoulder-top-computer a couple of tries to get it right. And if I can get it right, just about anybody should be able to do so. Be patient, as the directions state, converting the *.tif and *.tfw files to *.img takes about 10 minutes; each 4-5 minutes. Then loading the file into the Garmin via usb was 15-20 minutes. Final map size ~134 Mb.

    Helpful hints are found on line at Careful reading helps.

So was it worth it? Aside from the satisfaction of making the process work, there are negatives.

  • First, The NOAA chart is readible only when the scale bar in the GPS map window is 500 ft. Zooming out brings up the Garmin base map and zooming in reduces the image to dots.
  • Second, the image is on the grainy side, especially as compared to Garmin's MapSource topos.
  • Third, panning to different parts of the chart is very slow. The image disappears and then gradually fills in. Likely a bit too heavy a load for the Hcx's image processor, though at 5 kts motoring or sailing, the screen will, I am guessing, be able to keep up.
  • Last, determining where one is in reference to the surroundings is difficult because of the small screen size. It puzzled me and I had an idea of what to look for. This could be problematic in conditions of low visibility, or in unfamiliar waters or especially both.

There may be workarounds for some of these issues and I am open to trying them.  Suggestions most welcome.

So why bother? Some possibilities:

  • It could serve as back up to paper charts, or help determine location on a paper chart
  • Oregon, Dakota and other compatible Garmin units have larger screens or perhaps faster image processing than the Hcx
  • Better than nothing if paper charts or Garmin's proprietary software are not available

I plan on a stroll along our waterfront in the next day or two to see whether it will show my location and the shore accurately and remap at a walking speed. Time permitting, will try reducing initial file size (pixel count) to see whether a smaller file pans more easily among other workarounds.

Best,  Forester

p.s. Establishing a connection between the computer and Garmin took a bit of work.  Even though the Garmin and computer were connected by a USB cable, and the Garmin screen showed a connection and the computer showed the Garmin as "E:" drive , Moagu could not detect the connection until I rebooted the Garmin, twice I think, while leaving it attached to the computer via USB cable.  Also ensure the cable is stuck all the way on the Garmin.[/list]


I decided to see whether reducing map size would load and pan faster.  I didn't immediately see how to use MICRODEM to redcue file size, so I decided to reduce file size with Paint.NET and see what happened.

First reduced pixels on one dimension to 1/4 x 1/4 original number.  Processed and loaded files  (something like 5 tiles, 12 Mb) to Garmin with Moagu.  Result; the NOAA chart would not appear at any scale setting.  Hmmm...

Then reduced pixels to 1/2 x 1/2 of original (2 tiles, 40 Mb file).  Loaded to Garmin ok and it appeared at the 500 foot scale, BUT the image was smaller than the full sized file.  Handy for viewing river features, but it placed my house and adjoining burg in the middle of the river.  Just a bit inaccurate....

Then erased that map with sendmap20, and reloaded the full sized 134Mb version.  Took about 12 minutes to load.  Home and adjoining intersection are within ~1/100 minute of the first time I loaded the full map.  Maybe pixel error on the Garmin's screen.

If anyone could supply advice on using MICRODEM to reduce file size while keeping registry, I am open to feedback.  Thanks in advance.

Best,  Forester



Many of us here use Globalmapper for all kinds of projects. It's really powerful and can do just about everything. Very easy to re-sample raster imagery at any resolution you like. Looks like it will also open and save your .kap files.

If you get serious about mapmaking, you might want to have a look. It's not cheap, but personally I couldn't do without it. You can download the free trial here, which does everything but export data. In the past, they would give you a free key that would unlock all the program features for 30 days for evaluation if you sent them an e-mail too:

I've never used MOAGU but it looks like a pretty cool program. I have been developing my own methods and software to process raster imagery (discussed in another thread). I've split my current project into tiles that correspond to USGS quads (~6.5 miles x 8.5 miles), and have found that when they get larger than about 2.5 MB each, the gps starts to struggle with them. By keeping them mostly within the 1 to 2 MB size range, my different units (couple Nuvi's and a Montana) can draw the map in realtime, even while using track-up mode, driving 65 mph and viewing through the .3 mile zoom range. It still works fine at .5 mile zoom too, but I start to notice a little lag in the position of my vehicle. There are 87 of these tiles in the full map.

I think that MOAGU takes a different approach to converting raster imagery than me, so I don't know how much this will apply to you. But the size of the individual map tiles will still be very important. Are you saying that your map has 2 tiles that are 20MB each? If so, I think it's going to really tax most gps units. See if you can break it into much smaller tiles. Somewhere you should find the right trade-off between tile count and size. With Globalmapper, you can easily "grid" your source raster imagery into as many separate tiles as you like at any resolution you want it sampled at.


Moagu is a hack for older Garmins; a modestly clever hack, but with serious limitations. The limit on image size is due to limitations in the graphics library that I used; for images larger than 100 megapixels, the program is likely to choke. I hope to remedy this ultimately for my G-Raster program, but given the increasingly shrinking market for Moagu, it's unlikely to happen for that program.

It sounds like you're using the original Moagu format, which is a full point-by-point vectorization of the raster image into points. Decent for accurate reproduction, but painfully slow on any image that doesn't have mostly white as a background color; doubly so if you're not using one of the older faster Garmins, like the 60Cx or 76Cx. Resizing the image is unlikely to help, as it's the Garmin screen pixel density that affects display speed, not the pixel density of the original image. To get the image to display at a lower zoom level, set the "Detail" setting from Normal to High (but be prepared for even slower draw speeds).

I would recommend using Moagu's built-in BMap2MP GUI, as that's a front-end for a raster-to-vector conversion based on polygons, which will display much faster than a point-by-point (with some image degradation). The tutorial on this site should walk you through using that utility, and you will be much happier with the display speed, even if it will still be pretty slow. In either case, you will see some degradation of the image quality; can't be helped. You might try the MapWel raster to vector converter, as it seems to work somewhat better than BMap2Mp.

Finally, if you absolutely need these charts, you will absolutely get better results using actual raster charts on the newer generation of Garmins. The eTrex 20 is available for less than $200, the Oregon 450 is often on sale for about $250. And the newer Garmin GPSMap 78 series is designed for marine use (it floats).


Also worth noting that those models you mentioned (eTrex/Oregon/78) support raster maps with a maximum of 100 tiles. The Montana supports raster maps with 500 tiles, which will give you substantially more coverage. :)


Boyd and Leszepk,

Thanks for your detailed and helpful responses. Shows how far down the learning curve I am!  Will pursue your suggestions.  Best, Forester



Spent the evening trying different settings.  800 foot scale seems to work the best for NOAA chart 18532_2, the Columbia River from Bonneville Dam to Hood River, OR; a long skinny map; 500 foot scale was too close in.  Played with the color settings and tile sizes and they do change the image qualities.  Finally got a clean, four or five color, nicely readible image, but its 538 tiles and 201 Mb.  Whew; accomplished a bit of housework while it was processing.  Will try a couple more things to see whether file size can be reduced and image quality retained.  Will post results.

Best,  Forester

p.s. Thanks for the suggestions for the marine models. 


A bit more careful reading of instructions and practice with Moagu produced graphically good results; non-grainy image, simple legible colors, legible lettering and though slow to refresh, is likely speedy enough for a small slow sailboat. :)

Here are the settings:

•color setting: "checked"
•scale: 800
•tile size: "large"
•contrast: "left unchecked"
•combine: "yes"

*File size: 114 tiles, 94 Mb
*Display colors: non-grainy; land, tan; shallow water, light blue; deep water, white; lines, black; buoys etc., river mile markers, red. Numbers and letters are legible black.
*Refresh time: much better than the first attempt's 137Mb file. Ok for sailing.


*Tile setting "small" gave nice colors, 538 tiles, 201 Mb, and super slow refresh rate
*Checking "contrast" (with large tile size); colors were black, white and red; yielded 252 tiles at 58 Mb, good refresh rate but difficult to discern land from water because both were white.

Overall? Neat product. Maybe not as fast as Garmins' nav charts (have not tried 'em and which anyway do not seem compatible with the etrex vista hcx), but graphically good, the price sure is right and it should work ok for the nearby river. Plan on trying chunks of Puget Sound next.

Cheers to the developers! For those folks just getting their feet wet with this product, I worked my self into a blind alley more than once. Keep trying. Keep reading the instructions. What helped greatly was to set up a unique map file name for each run,#####_#abcd, based on chart's number with letters indicating key settings. For each run, record the file name, settings (map number, which settings were used, etc.), and outcomes (tile number, file size, colors, refresh rate, etc).

Best, Forester

p.s.  20120218, Discovered that the NOAA chart disappeared from the Etrex when batteries are low, however, it reappeared after installing fresh batteries.