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I'm trying to load a Garmin map designed to work on a 1gb card. My computer only sees 940mb capacity when there is an empty "Garmin" folder on the card. The file is "1000MB-lon_-82.79_to_156.09.gmapsupp.img" and is 945mb. I tried reformating the card (FAT32) to see if I could make my computer see more capacity, but it didn't change. Are there any tricks to getting these files onto what seems to be an appropriately sized card, or am I always going to be stuck with a 1/2 empty card?

asked 11 Jun '11, 23:32

bumbee's gravatar image

accept rate: 0%

It sort of doesn't work like that....

In computer terms,

8 bits = 1 byte; 1024 byte = 1 kilobyte; 1024 kilobytes = 1 megabyte; 1024 megabytes = 1 gigabyte; 1024 gigabytes = 1 terabyte

Whereas, retailers use a different measurement system, where they are equating 1000 megabytes to a gigabyte.

Obviously, this means they can sell hard drives and SD cards as 1GB, but they will appear to the computer as being less than that, i.e. your 940mb card.

You need to either make the garmin file smaller, or buy a bigger card.

Cheers Chris

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answered 12 Jun '11, 09:13

c2r's gravatar image

accept rate: 18%

2gb or 4gb cards are fairly cheap and the map is growing so its best to get a bigger card,you'll grow into the half empty bit anyway. I also find its simpler to download the latest map every two weeks onto the spare card.

(12 Jun '11, 10:00) andy mackey

I'm guessing that whoever you're getting the map from is trying to size that to fit on common size cards - I'd have a word with them mentioning that their 1Gb map doesn't fit on your 1Gb card. Obviously the usual caveats apply - they're using their spare time creating these maps so I wouldn't expect an instant solution from them.

Another option is to make your own map - search this help site for mkgmap (which is the most commonly-used software to do that) will find some pointers. There's also a wiki page. One advantage of creating your own map is that you can make the map as small as you like by restricting the area that you create the map for - the longitude in your download file name suggests that it includes most of the USA and Canada, Mexico and New Zealand. Assuming that you don't want ALL of those it should be quite easy to create a smaller file.

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answered 12 Jun '11, 10:28

SomeoneElse's gravatar image

SomeoneElse ♦
accept rate: 16%

edited 15 Jun '11, 07:50

ALE's gravatar image


@SomeoneElse -- Yes, the map I've found on OSM says it's specifically supposed to fit on a 1gb card. It's just the USA, but covers west to Alaska and Hawaii. Much more than I need, but is a ready to go map that I SHOULD be able to load and go without downloading and learning several other pieces of software. The "500mb" series didn't have one that covered the range I need. I believe I've found a source that will load into MapSource so I can pick the sections I need without filling an entire card. The best things in life may be free, but that doesn't make them the easiest. After I've taken the road-trip that the maps are needed for I'll have time to learn more resources.


(13 Jun '11, 04:35) bumbee

Whereabouts did you download the "1Mb" map from? It's probably still worth letting the creator know that their 1Mb maps don't fit on 1Mb cards. Whoever it is it's unlikely to notice this help question (and they might not be in a position to resolve it immediately for the reasons mentioned above, but at least they'll know that there's an issue).

(13 Jun '11, 12:26) SomeoneElse ♦

@SomeoneElse: I edited your answer because it is Gigabytes and not Megabytes.

(15 Jun '11, 07:51) ALE

@ALE - thanks, it's all Greek to me...

(15 Jun '11, 09:28) SomeoneElse ♦

I don't know what Garmin model you have, but from my experience a 1 GB map will put a serious strain on your device hardware and make the map draw quite slowly, especially with home-made maps (i.e. the ones produced using non-Garmin software).

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answered 13 Jun '11, 06:43

Breki's gravatar image

accept rate: 10%

I use a 4gb that works ok on my vista HCX but it is one of the later faster HC micro SD cards, they also allow cameras to take successive photos in a shorter time and the map transfers faster from PC to this memory card compared to a standard one.

(13 Jun '11, 22:20) andy mackey

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question asked: 11 Jun '11, 23:32

question was seen: 5,803 times

last updated: 15 Jun '11, 09:28

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum