Pear cordons against a fence

[ameno]

Yes, that's the graft union, and that should indeed remain at least an inch (ideally a couple inches) above the soil surface.
There are two reasons for this. One, as it is a wound it is more prone to infection, and if its buried then infection could get in and cause the graft to fail. The second reason is that if it is buried then the scion could start to produce its own roots, and you don't want that as you would lose all the benefits of the rootstock (like dwarfing, precocity, disease resistance, etc.)

[Rapscallion]

Thanks Ameno.
have I got it the right way up?

[nickdub]

As long as the roots are below the ground and the union is not, then you should be fine.

As an aside the ground looks very dry under the fence which, if so, would mean you need to do a lot of watering of the trees first year.

[Dave8abond]

The part in the centre of the circle is where the bud of the desired cultivar grew from . If it was propergated by budding, anything lower than that will be rootstock. If it was bench grafted the graft union will probably be 2 to 4 inches below.