Backcountry explorer and US Topo maps

These are the 2 apps I am running on my Lenovo tab 2 A10. have many many questions, It seems like it is nearly impossible to download tiles form either app a t a decent size zoom /detail level I like to be able to see level 15 but that often uses like 7 million tiles. and takes days to load.

The US topo maps is 2017 Atlogis geoinformattics Gmbh & co

It says I can cache maps for offline navigation so what I was attempting to do is one star roughly on 1 each card either 32 , 64 or 128 gig. When I do that it says removal of the card will erase the data> which seem swirl to me and scary enough that I haven't removed the card.
How do make sure the data won't be erased?

So are there any preloaded option for sale. The tablet uses a micro sd card.
Is there any tutorials on the net that address some of these issues. '
I have the same issues with Back country explorer

 

Topo USA is a Delorme product that installs as an application on a PC with maps of USA and also can load maps to an Earthmate GPS device.

There is an Earthmate Android App. After installing it prompted me for a Garmin paid account or to pair it with a Bluetooth device? I'm not certain how it works exactly in order to load maps, i.e. I think it requires a Garmin paid account to download maps and possibly another device with maps to pair with?

https://buy.garmin.com/en-US/US/p/577212

https://play.google.com/store/apps/details?id=com.delorme.earthmate&hl=en

US Topo Maps the app you're talking about is a free Android App. I haven't yet installed it on my Android. I'm currently working with Osmand that has state maps that can be downloaded. Doesn't really have topo maps but maps from different sources can be set to topo with contours and hill shades.

There is also Back Country however it doesn't appear to have options to download state or region maps. Maps are downloaded by selecting an area from an overlay map to download smaller and more specific areas. Documentation states you can download larger areas which potentially creates larger than normal map files. So users often only download the map areas they need and not an entire state or region.

 

Backcountry Navigator has some what they call Premium Add-Ons

https://crittermap.zendesk.com/hc/en-us/articles/115001513063-Premium-Add-ons-Map-Pricing

Backcountry Navigator has a warning about selecting an area the size of a state for downloading.

"State size downloads at full resolution are much too big to fit on your storage card. They could be upwards of 50 gigabytes. There are reports of the app hanging in a download because the size is simply too large."

https://crittermap.zendesk.com/hc/en-us/articles/215564623-Don-t-Download-State-Size-Maps-

Handheld devices such as PDAs, Smartphones, Tablets, etc. use a different type of OS designed for smaller, portable and mobile devices.

Can't really deal with large data files the same as PC applications. Probably is one reason whey you don't see full blown apps for use with a smartphone, pda, etc.

Another thing I notice is the data files such as map files are much larger for a handheld device and it's OS than that of a PC.

E.g. I have Delorme Topo North America 10.0 installed on my PC after installation the size of the map (comprised of data files) installed on my hard is 6.98 GB. The map covers the entire North America and Mexico for Topo & Street (2D & 3D), road and trail data, added more than 800,000 new road names in the U.S.; highly detailed lake, river and stream data for all 50 U.S. states, data for 38 US national parks and 100 provincial parks in Canada, as well as elevation data for all of the U.S., Canada and Mexico

Delorme Topo uses *.dat *.ind *.ddm *.v *.vi files for map data. I'm uncertain about their structure, I think a DAT file is similar to a DBF (database) file, IND I think is an index file, the others I'm less certain about.

After installing the paid version of US Topo I found my state (ranked 18th in square miles), was only able to shrink to a min of ~31 GBs from 32+ GBs. This is the size of a downloadable map file for only one state.

I'm not certain of all the technical reasons but assume it's a matter of difference between the type of programming and hardware architectures of PC and handheld devices.

PC maps appear to be much more compressed. A mapping app designed for a smart phone I would guess won't be able to utilize map data the same as a PC application which requires more system resources such as memory, disc space, etc. I'm only guessing but think a smartphone map app may use a different type of map structure where the map data is more easily accessible by a smartphone app that takes up fewer bytes of memory and drive space.

If a data files are compressed I would think additional code would be needed to decompress and read the data. Perhaps the more a data file is compressed the more difficult it becomes to decompress? You would need to ask a programmer who works with this type of programming.

I don't know all the technical reasons, only that the map files created for handheld devices and their map apps are much larger than map files used for pc map applications.