ground boundary in a sentence

1. A gun battle broke out earlier this month between the villages over grazing ground boundaries, followed by tit-for-tat shootings this week.
2. Although there's a heated battle going on over how far to expand the urban ground boundary, the basic concept is as much a part of Portland as rain.
3. It models vegetative fuel either by explicitly defining the volume of the vegetation or, for surface fuels such as grass, by assuming uniform fuel at the air-ground boundary.
4. It's difficult to find ground boundary in a sentence.