GR translation: across the heath over the giant grave-mounds

[Mike Jing]

V747.5-12, P761.36-762.4   He appears first with boots and insignia shining
as the rider on a black horse, charging in a gallop neither he nor horse
can control, across the heath over the giant grave-mounds, scattering the
black-faced sheep, while dark stands of juniper move dreamily,
death-loving, across his path in a parallax of unhurrying fatality,
presiding as monuments do over the green and tan departure of summer, the
dust-colored lowlands and at last the field-gray sea, a prairie of sea
darkening to purple where the sunlight comes through, in great circles,
spotlights on a dancing-floor.

The published translation thinks the phrase "over the giant grave-mounds"
modifies "the heath", meaning the heath is on the other side of the giant
grave-mounds. Is that actually correct? Somehow it doesn't feel right to me.