Other apps put the grave where YOU stood, not where the stone is. Photograph a west-facing stone, then an east-facing one, and the dots zigzag all over the row. Dot On The Stone uses your phone's compass to put each dot on the stone, and lets you drag it right where it belongs.
Everything stays on your phone. Nothing is uploaded unless you choose to share it.
Open the AppExample: the Plant Cemetery map, where every grave dot was walked and fixed by hand.
This is a free test version. Please tell us what works and what doesn't.