Size of the altimeter

Do you mean the result of SensorHistory.getElevationHistory()  ?  the easiest way is to count the number of samples using the iterator.  When you first turn on a watch, it can be zero and grows over time to some limit (often something like 4-6 hours of data, with each sample being a minute or two apart.)

Sorry. I wasnt that clear. I mean before I use the iterator. I can directly get the newest, oldest, min and max value. And exactly at that point I miss the size. 
is it possible, that the heart history is bigger than the heigth history. On my VA4 it seems to be once 360 and once only 180?!

When you make the call you can specify oldest first or newest first, and you can see the min and max

When you first get the iterator, use

min=iter.getMin();
max=iter.getMax();

Exactly. And now count=iter.getSize()?

Like I said you have to walk the samples and count them,  You can also specify the number of samples or use the timestamp with the :period when doing the getElevationHistory() call.

Ok. Thank you