How to calculate roaming cost?

Since this is 'Other' section, I thought it would be a place to start this topic.

I am interested if anyone has any idea how to calculate roaming cost if you have these variables:

Device: TK103A (gps103 protocol) (How big is the data package?)
Send data interval: 30s (apart from SOS and acc on and off signals)
The charging interval of the telecom operator is 10KB + 10KB.
Roaming cost:

• GPRS (Euro/MB) MB: 13,16Euro
• GPRS (Euro/10kB) 10kB: 0,1285

One message with GPS info is less than 100 bytes (GPS103 protocol), but if you add communication protocol overhead (establishing connection, headers etc) it would probably be slightly more than 100 bytes. Then you need to add heartbeat messages (about 20 bytes long).

So, let's say roughly 200 bytes per message, then the device would use 25KB of data per hour.

Note that this calculation assumes ideal connection. If connection is lost most likely your telecom operator will charge minimum chargeable unit (which I guess is 20KB in your case). This means you can get changed for 20KB even if you used only 100 bytes if the reception is poor.

I'll be traveling for a week soon and I will test 2 devices and see how they behave, and what the cost is going to be.
If the device looses the connection, or it drops out, I'll be able to notice that on the server, correct?

I believe that worst part is when switching networks, when the road is close to the border, signals overlapping.

I'll definitely report back here when I come back...

Maybe, just maybe, there is a way to come up with some approximation formula...

Thank you.

Yes, you should be able to see re-connections on the server (in logs).

Well, here is the update:

I spent 8 days in roaming, and upon my return, I requested detailed listing from my telecom provider:
SIM card used 1,33 MB data while in roaming - roughly around 16 Euros...

I am now looking at some global SIM cards...

Any suggestions?

It's not too bad. How many GPS reports did you get from your device?

I received them regularly, every 1 min, except while device was searching for network. But I can see inconsistency in connection while in roaming.

This is part of the listing while on home network and sending info every 30s:

This is part of the listing while in roaming and sending information every 1 minute:

Looks like the connection is not as stable as in your home network.