How to reduce the size of a gmapsupp.img file on a card???

**Boki** · 25th September 2017, 09:25 PM

Two notes:
- for older devices, reading larger cards is not firmware then hardware problem. The same goes for older standalone (USB) card readers. You have reader and following chip projected to read exact type of cards. No firmware helps there.
In fact not size of was problem card then type. Older cards don't have class. There were also 4GB SD and CF cards (I even saw 8GB SD industrial), but in that time they were extremely rare and expensive. Especially those declared for high speed (4GB SD 150x were fastest then and damn high price, I bought 2GB).
- It's good to have a quality card. But the fact that you use Class 10 is absolutely unnecessary. Your device (or any other navi) can not use its speed, nor the amount of data it reads from them requires such a flow. The fact is that quality cards class 2 meet the requirements of such devices.
Free explanation: High Class cards (speed) are today needed mostly for digital cameras, when card have to record several MegaBytes large pic in only 1/10 of a second. Clear? And of course, you need even faster to transfer all of the recording to your PC

P.S. Capacity of chips on cards and other flash based memory is whole 2/4 or more GB (Giga Bytes). BUT. But addressing, file system of the chip itself and spare blocks take away the useful space and for the user stays less....
There is even a worse situation with modern hard drives (and some other devices - who said Mobile Phones

) where even firmware is located in memory chip(s).

**osiris4isis** · 25th September 2017, 09:36 PM

Originally Posted by jinxxxxxx

When you find that you can't load all of the USA from the 2018.20 mapset I ques you will just have to use 2 2gb CF cards.

In reality it doesn't matter how much data a card can hold if it can't hold all the data you need it to hold it is of little use. And I do know what I'm talking about.

Please stop posting nonsense. USA map 2018.20 is less than 2GiB. Even if you find ANY map that's more than the memory card you're using, you can still reduced it via MapSource.

Originally Posted by jinxxxxxx

Now I only use Sandisk Class 10 for my maps if you guy are dumb enough to trust unbranded memory that says a lot about you.

Nobody said to "trust unbranded memory." As a matter of fact, we posted it to persuade/warn users not to trust it and more importantly, WHY not to trust it.

It's clear to me from your many replies that YOU have no clue what you are talking about. Let the posts be self evidence of who knows what.

**Butters** · 26th September 2017, 04:09 AM

Well, to be precise the Lower 49 USA 2018.20 supplied as a compiled img file by Garmin via GarminExpress is 2,053,636,096 bytes or 1.91259765625 GiB (BINARY gibibytes) so won't fit quite on my Sandisk (so-called 2GB) cards which have barely more than 1.90 GiB of available space and definitely won't fit on any '2GB' microSD/SD which never seem to have more than 1.87 GiB available.

GMapTool info:

Code:

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The CF card isn't short by much though.

However the Lower 48 USA without any Caribbean Islands or Hawaii is able to fit on my '2GB' cards, which have usable space of 2,047,541,248 bytes, just a tad over 1.90GiB, with 5.06MiB to spare because the bare 48 states img is indeed well under 2GiB. Here's the proof:

MI USA Lower48

Unfortunately going from past experience with others who are unable or unwilling to get their heads around this stuff, I doubt our East Coast gentleman will acknowledge his misconceptions despite the clear evidence offered. It all comes back to confusion/conflation of decimal and binary forms of 'gigabyte' and an unwillingness by ppl to do the maths. He's hardly the first and won't be the last.

**Monz** · 16th March 2018, 09:01 PM

In fact it's exactely what I want to do (to be able to have the Countries or states of my choice ) because even if my Goldwing is able to read cards bigger than 2GB, it won't read the .Img file larger than 2GB.
I don't understant all that is written on this post but it looks as if the solution is there.

For now, I have to use two CF cards. One with the 2019 Canada maps (432 000 Ko) and swith it to an old North America under 2GB when I need to go to the States.

**Butters** · 17th March 2018, 12:29 AM

@Monz
Yes the solution is there. The only reason you don't understand fully what's written is that you and many more people haven't yet understood the confusing difference between the original binary interpretation of a gigabyte (which is now more correctly known as "gibibyte") and the more recent decimal interpretation of gigabyte. 1 gibibyte has a value of 2 to the power of 30 bytes or 1,073,741,824 bytes (i.e. put more simply, a multiplication factor of 1024 to higher values, bytes>kibibytes>mebibytes>gibibytes etc.) and the abbreviation of gibibyte is "GiB".

The term gigabyte now is usually given a decimal interpretation where 1 gigabyte has a value of 1,000,000,000 bytes (10 to the power of 9, or a factor of 1000) and it's abbreviation is "GB". I say usually because Microsoft is sticking stubbornly with the original binary interpretation which adds to the confusion seeing Linux and Mac OSs now both use the decimal sense for gigabyte. That seems even more weird as MS's Windows OS runs in base 2 but actually displays storage capacities using the current prefix for base 10. In their defense they're simply sticking with the original binary interpretation of those prefixes.

So, you can maybe now clearly see that 2 GB is 2,000,000,000 bytes but 2 GiB is 2,147,483,648 bytes. Also your so-called 2GB CF card only has effective storage available of ~1.90 GiB or 2,047,541,248 bytes. Your garmin-based GW Navi can actually read an image up to the FAT 16 file size limit which is one byte less than 2GiB or 2,147,483,647 bytes so by using a card larger than your 2GB CF you can get a slightly bigger img file on it, almost 100,000,000 bytes or ~10 MB larger in fact. If you have a later model GW with an SD card navi then your 2GB SDs have even less space than a CF.

If you've got your head around the above info, you'll now understand what's written in Post #23. If you still don't get it, read this page:

Code:

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**osiris4isis** · 17th March 2018, 12:42 AM

Originally Posted by Butters

So, you can maybe now clearly see that 2 GB is 2,000,000,000 bytes but 2 GiB is 2,147,483,648 bytes. Also your so-called 2GB CF card only has effective storage available of ~1.90 GiB or 2,047,541,248 bytes. Your garmin-based GW Navi can actually read an image up to the FAT 16 file size limit which is one byte less than 2GiB or 2,147,483,647 bytes so by using a card larger than your 2GB CF you can get a slightly bigger img file on it, almost 100,000,000 bytes or ~10 MB larger in fact. If you have a later model GW with an SD card navi then your 2GB SDs have even less space than a CF.

This is assuming
1. There are no bad sectors that would give less space than the "theoretical" limit
2. Taken into account of overhead of the FAT table

**Butters** · 17th March 2018, 01:18 AM

Originally Posted by osiris4isis

This is assuming
1. There are no bad sectors that would give less space than the "theoretical" limit
2. Taken into account of overhead of the FAT table

Yeah sure, let's confuse 'em a little bit more hey?

Anyway, i think bad sectors are ignored by the OS after a re-format (aren't they?), not even shown in used, free or total capacity and the overhead of the File Allocation Table is already accounted for when looking at available fee space in properties, which for this recently formatted 2GB CF is 96KB in overhead:
[Only registered and activated users can see links. ]

**osiris4isis** · 17th March 2018, 01:38 AM

That's correct. Unless you use specialized proggy to examine it. My point was if you're using "theoretical limit" in your math; you need to be aware, that you might get less. Don't forget, sector size* play a role in size used as well. A lot of small files will take more space than a single file of the same size.

* An important factor used in FAT, FAT32 or NTFS

**Butters** · 17th March 2018, 02:26 AM

Ok, i see what you were getting at now and i agree, it's theoretical maximum. As you may get less, all the more reason to use a 4GB SDHC card instead of a 2GB SDSC one in such devices. That way you'll maximize the image size right up to the FAT16 limit of 2,147,483,647 bytes .... or if using a device that can see up to 4GiB images in FAT32, utilize an 8GB card to maximize to the FAT32 limit of 4,294,967,295 bytes. Also, in some old devices that do refuse to use a 4GB card simply format as FAT16 then create a partition of 2GiB leaving the rest allocated.

**osiris4isis** · 17th March 2018, 02:28 AM

Give that man a medal. But not as shinny.

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