Thread: Why is 'Suppmap1' in Nuvi 1xxx Inventory? & Why are some maps unselectable named as 'gmapoem'?

2^10 vs. 10^3
Historically most people defines 1 kilobyte as 2^10=1024 bytes, 1 megabyte as 1024 kilobytes, 1 gigabyte as 1024 megabytes and so on. That's the definition that was used in the beginning of calculating bits and bytes in computers and PCs.
Storage manufacturers have hijacked the term and by political and technical lobbying got the SI definition of decimal counting for kb, MB, GB, TB etc. to be commercially accepted. They claim that k stands for 10^3=1000, M for 10^6=1000000, G for 10^9=1000000000 and that it allows them to use the decimal definition of prefixes for bytes. That even despite the de facto standard for computer science had been binary 1024 calculated prefixes for decades.

When we where using kB and MB it didn't matter so much if it was decimal or binary definition behind the symbols. But we loose approx. 2.34% for each step in the k -> M -> G -> T -> P ...
1 kB is ~97.66% of 1 KiB
1 MB is ~95.37% of 1 MiB
1 GB is ~93.13% of 1 GiB
1 TB is ~90.95% of 1 TiB
1 PB is ~88.82% of 1 PiB
...
...
So with TB and PB we have lost close to 10% or more from what many of us actually expected from binary calculated units.

Gigabytes vs. gibibytes class action suit nears end

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Microsoft still uses the term gigabyte (GB) as calculating 1024 MB or 1024*1024 kB or 1024*1024*1024 bytes. I'm also using 1 GB as 1024 MB in normal everyday life but tries to be as accurate as possible here in the Noeman forum. So here at Noeman I'm trying to use KiB, MiB, GiB when appropriate. Most file host forums also shows MB but uses binary calculation such as it should be displayed as MiB instead.

We could even complicate it further by using the original definition of a byte - one data word used for CPU calculation or data storage. That means 1 byte = 4 bits in a 4-bit CPU world, 1 byte = 8 bits in a 8-bit CPU environment and so on. In my Windows 7 64-bit OS that would mean 1 byte = 64 bits.

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2^32
If you have a FAT32 file system it means the address space is 32-bits. Calculating from address 0 (zero) and up to 2^32-1. The -1 comes from that you start with address 0. That's the maximum unsigned 32-bit integer that could be used in linear addressing. This is equal to 4 GiB - 1.

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Some (un)usefull historical data
In the old DOS days with 16-bit application there was a lot of tools like DOS Phar Lap Extender to break the OS limit of 16-bit addressing. By using such extenders they could write 32-bit applications to run in a 16-bit OS.

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About the total numbers of map families (MapIDs) that can be used at the same time in a Garmin unit.
I haven't tried to measure this by science and taking the time to test my Garmin units. If I load my 32 GB Samsung Class 10 microSDHC card with 4 City Navigator NT, 7 TOPO maps and 6 BC g2 the result is that some maps is not seen by the unit.
Perhaps Mapperoni would be kind and share his more exhaustive evaluations of that subject. I think Mapperoni tested the capacity of a GPSmap 62 unit with TOPO Norway Adventure. There's a total of 20 maps in that series and all have a different MapID.

I thought the limits put on the map size ( Especially for units like the Montana 650 ) was based on how many "Tiles" were in am image and not the actual size of the image file.

I can't recall exactly what the tile limit was, but it was somewhere around 2025 tiles I thought for official Garmin maps.

For "custom" maps, the tile limit on the Montana used to be 100, but has recently been increased to a 500 tile limit for "Custom" maps on the Montana.

It will also depend on whihc GPS unit you are using and which Firmware/Software version.

If That Topo Norway Advenbture has more than the allowed number of tiles than the GPS will not work.

If there are 20 Map "Families", there well may be over the allowed number of tiles... I don't know.

There may be a way to movfe some of the tiles into another map image file and turn both the img files on using the Montana and they "may" both show up as one "may" overlay the other.

BTW.... I'm not an expert. Like many here... I'm still learning.

@timp4411

Some of the previous models have a limit of 2025 map tiles. The Garmin Oregon and Montana can handle at least 4000 map tiles.
Sorry if I didn't gave the full background but there's at least what I wrote in post #2:

Originally Posted by Ballebar

About the 4 GiB barrier!

Well, you can put as many <= 4 GiB map files as you want in the Map directory of your memory card. As long as there's room for all the files anyway.
The problem is other constraints like how many map tiles your unit supports and the most severe constraint about the number of map families it can support.
If I store all TOPO Norway Adventure in one gmapsupp.img then I have 20 map families there. That's NOT readable by any Garmin unit I've tested including the Garmin Montana 650t. Normally it works with 16 or 17 MapIDs as the total for all maps but not with 20.

All the problems with map families have been discussed in some other forums by other users. There's special patched variants of TOPO Norway Adventure with one single MapID for all 20 regions. I believe that Mapperoni is the creator of one such release.

The full installation of TOPO Norway Adventure have 727 map tiles and it would generate a file size of 1.24 GB according to MapSource. So it's well under 4000 or 2025 map tiles and also lower than 4 GiB and even less than 2 GiB.

Hi Ballebar,

Sorry for not reading the post from the beginning as you had already discussed the tile limitations.

Obviously, tile limitations are not the problem this time.

Have a great day !

Regards.

Originally Posted by Ballebar

2^10 vs. 10^3...............

OK, here comes another rule break .....THANKS, Ballebar!

NOW i've got my head around it. I just wish i had found something as clear and easy to understand as that when i searched outside for it. There would be other 'village idiots' high-fiving themselves after reading your post too (sorry timp4411, i didn't mean you, i mean me). Surely you could find a place for that explanation post as a tut/guide somewhere else as well... i'm betting it would helpful be to many, many others. System wouldn't let me Rep you again so soon, but it will happen. Maybe others can and will. I may sleep without shiraz tonight... nah, i'm gonna have it anyway .