Question with GPSMAP 62s and lotsa maps

[jimby]

Hi guys,

Just bought a 62s.  I am also an owner of a GPSMAP 60C as well.  I'm a relatively old hand at loading and managing maps.  I also updated the 62s firmware to the latest version and I am using all the latest Garmin software.

I am aware that the 62s allows you to create .img files with different names so you can avoid having to glom all the maps together in Mapsource as needed by the 60C.

So, I have a 62s with a 4GB microSD card that is about half filled.  I have about 8 different maps that I can enable and disable at will. I also have a the unit base map and a City Explorer map stored on the unit's built in storage.  All of this works just fine.

The issue I am having is this:  I have loaded the entire CA Topo map (available on this site) onto the SD card, and given it an appropriate name (ca_topo.img), but it doesn't show up in the map management on the 62s menu.  Now, if I select only half of the tiles (just southern CA, for instance) in Mapsource and load half the map onto the SD card, it shows up just fine with my given file name. Ditto with loading it into the 62s' internal storage.

Am I hitting some sort of segment or memory limitation of which I am not aware?

Thanks,
Jim

[Boyd]

Your unit has a limit of 4,000 segments. I don't think there's any easy way to know how many you have used on the device itself. You would probably have to look at each of the maps in mapsource and tally up the segments.

Older maps tend to have smaller segments for the sake of compatibility with older GPS'es that had tiny amounts of memory. Segment size is chosen by the map author and there are no standards. The DVD version of US Topo 100k contains about 6,600 segments. So you could max out your unit very easily if you loaded a big chunk of that.

There can also be issues if two maps share the same Family ID number (FID). That would cause the unit to group them together and you wouldn't be able to individually enable/disable them. Again, this code is chosen by the map author and with 3rd party free maps, it's just "luck of the draw" when it comes to hitting duplicates.

[jimby]

Thanks Boyd...I guess I probably hit the 4000 segment limit of the device.

My dreams of having the whole planet mapped to 20 ft CIs is shattered. 

j/k

Too bad there isn't a program out there that can combine map segments to make them larger but fewer (to take advantage of the new units' RAM)....


Regards,
Jim

[Boyd]

It could be done, but this site frowns on modifying the work of another author.

BTW, just to nitpick a bit, we aren't talking about "RAM" here. That is generally used to refer to the high speed memory used by the processor to crunch numbers and is typically only 64 to 128MB (MB, not GB). Maps are stored in flash memory and it would be more correctly termed "mass storage", like a disk drive. 

[jimby]

BTW, just to nitpick a bit, we aren't talking about "RAM" here. That is generally used to refer to the high speed memory used by the processor to crunch numbers and is typically only 64 to 128MB (MB, not GB). Maps are stored in flash memory and it would be more correctly termed "mass storage", like a disk drive. 

Actually I was referring to RAM.  I assumed that when you said that in the past map segments were designed to be small as older units' memory was limited that you were referring to RAM. Or were you referring to storage when you said "memory?"

The newer units have larger working memory (RAM) that I assume could handle larger segment size. Maybe I am incorrect in this assumption?  Or are these arbitrary limits by Garmin on segment size?

I wasn't referring to mass storage; mass storage is cheap & large these days

[Boyd]

No, you are still confusing RAM and mass storage. "RAM" is high speed memory that you cannot access in any way on the gps. It is used to run the operating system and do calculations. It is only available to the system itself and is not used for map storage.

Your GPS has internal flash memory and also a slot for a flash memory card. Flash memory is mass storage. It's formatted as FAT32, just like a hard disk. The maps are stored there along with some other system files that are user-accessible. Older GPS'es also had internal flash memory for map storage, but it was tiny by today's standards.... like 8MB for example.

Yeah, it gets real confusing because we commonly refer to "memory" but really mean "mass storage". I'm just as guilty of this as the next guy. 

[jimby]

Hi Boyd,

I am not confusing the two. I know the difference.

If you read my last post carefully, you will see where the misinterpretation occurred.

[Seldom]

I'm having some map visibility problems that I mentioned over on the map-making list.  I don't think I'm over the 4000 segment limit, but is there any way I can tell exactly how many tiles my OR300 thinks it has?

[Boyd]

OK Jimby, I see that you assumed I meant RAM when I said memory. I think? Anyway, it's all good.

If you wanted to count map segments and didn't want to go through the process of selecting everything again in Mapsource and counting tiles, I can only think of one other approach. You could use either Sendmap20 or gmaptool to open each map file that you've placed on the Oregon and count its segments. There's no button that you can press on the Oregon itself to provide that info (AFAIK).

[Indrid Cold]

use MapSource and select receive maps from device and it will give you a list and tile count (as long as you only have a gmapsupp.img file loaded.

[maps4gps]

My dreams of having the whole planet mapped to 20 ft CIs is shattered. 

By the time appropriate source data is publically available to create 20 ft coutours of the whole planet, the 4000 segment limit will likely be ancient history.  And what of the other data which makes a map?  Currently the most detailed coverage of the entire world's land surface is 1:1,000,000.