What does "send to device" really do?

There are a few threads on here that indirectly shed some light on that process. They typically are discussing the inability to delete waypoints on a particular gps device from within BaseCamp.

What usually happens is that BAseCamp will send the information over in a file having a specified name, e.g., temp???.??? (Sorry I can't remember the file name) then the unit will, usually on the next power cycle, combine that file with its normal internal data file. The units seem to differ in their details. The earlier devices rend to be very protective of their internal files hence BaseCamp is unable to delete stuff from the unit and therefore the only way to make data go away is by doing it on the unit.

Now Garmin seems to be expending much more energy trying to rationalize the interactions among their devices and software and improve the communication between the hardware and software teams.

Symbols don't necessarily match between Basecamp and Garmin's devices, so if you try to send a symbol that doesn't match you'll get something else.

On the nuvis it works as Augustfalcon mentioned, Basecamp creates a file called temp.gpx that is merged on boot. This in itself can cause issues as if you don't delete that file later you'll never be able to delete the waypoints/favourites it contains. Nuvi files cannot be deleted via Basecamp.

Most recent handhelds on the other hand allow deletion using Basecamp.

I think the eTrex Venture HC uses the Garmin USB protocol and not mass-storage (or MTP) mode. Therefore the talk about the temp.gpx file is not applicable.

The Garmin USB protocol does not allow items on the device to be deleted. It's a limitation of the device, or more precisely the protocol, itself. You can read and write data--that's it. Now when sending a data item that already exists some models overwrite the existing item and others create a duplicate (e.g. with a '1' at the end of the name). I don't know what the Venture HC does.

If I modify track in BaseCamp and then write to the device, I guess I see two tracks on the device: track and track 1. But which is which? In other words, do I want to preserve track1 and delete track, or is it the other way round?

Well if you didn't make any changes then which ever (track1 would be easier since you don't have to do a rename as well). If something changed presumably you want to keep track1 and delete track.

IMHO, trying to synch and keep track of different sets of objects between the device and BC can be mind-boggling. It's possible to eliminate the issue by following a strategy of:

1. Keep everything you need or have ever used and might need again in the BC database - waypoints, routes, etc.
2. For a trip, have all needed items in a list unique to that trip and create any new routes there, including new routes that are modifications of existing routes. Name every item in a clearly descriptive way.
3. Before connecting the device, turn it on and delete everything that was on it from previous use, including the log file assuming you have previously downloaded any desired tracks from previous use.
4. With the device empty, connect it and send the entire list containing the trip data to the device.

With this method, all questions of route comparisons, unique route naming, multiple versions of items, etc., are resolved within BC and all changes are kept in one consistent place.

I think the eTrex Venture HC uses the Garmin USB protocol and not mass-storage (or MTP) mode. Therefore the talk about the temp.gpx file is not applicable.

The Garmin USB protocol does not allow items on the device to be deleted. It's a limitation of the device, or more precisely the protocol, itself. You can read and write data--that's it. Now when sending a data item that already exists some models overwrite the existing item and others create a duplicate (e.g. with a '1' at the end of the name). I don't know what the Venture HC does.

Hmmmm, uh, let's see, MTP is not a mass storage protocol. ;)

It is a Media Transfer Protocol that can allow other-than Media files to be transferred to a Host device. MTP devices can not be mounted as a Mass Storage volumes on a computer they are typically represented as a Media Device: Mac OS X does not support MTP well. USB on the other hand does support Mass Storage Class and was designed for the purpose of having the device "look like" a mounted storage volume.

Garmin uses USB MSC (UMS) and the protocol does support the deletion of files from the device with either the computer (Explorer or Finder) or with BaseCamp v4.2.2; but the device still has the final say. I believe that the eTrex will allow file deletion. If you have a Garmin device that uses UMS and you can not delete files on it then Garmin has chosen to limit that operation. I have no problem deleting files on my Montana or my fenix for example.

Hmmmm, uh, let's see, MTP is not a mass storage protocol. ;)

Which is why I said or :p I'm well aware of the differences.

The Venture HC supports the proprietary Garmin USB transfer protocol. It does not support mass-storage mode. It does not support MTP mode either. There is therefore no mechanism to transfer files (of any type in any direction).

Which is why I said or :p I'm well aware of the differences.

The Venture HC supports the proprietary Garmin USB transfer protocol. It does not support mass-storage mode. It does not support MTP mode either. There is therefore no mechanism to transfer files (of any type in any direction).

I bow to your sir...I mis-interpreted your "or" as implied reference to Mass Storage Mode rather than "in addition" to. :o