Bridge crane vs gantry crane in a log yard: how to tell them apart from above

If you're scanning a satellite pass or a flyover shot of a sawmill, nothing in the image comes with a label. You've got shapes, shadows, and rail lines, and you have to figure out what's moving logs and what isn't. Bridge cranes and gantry cranes get mixed up constantly in this kind of read, even though on the ground they look nothing alike. From straight overhead, the usual landmarks disappear and you're left with roofline, footprint, and rail track. Here's what actually separates them from up top.

What a bridge crane looks like from the air

A bridge crane rides on rails bolted to the walls or columns of a building. It lives inside a structure, almost always a mill building or a covered log storage shed with a green chain running through it. From directly overhead you won't see the rails at all, since they're mounted inside the walls, not on the ground. What you're looking for instead is the building itself: a long rectangular roofline, sometimes with a raised monitor section down the ridge where the bridge girder has clearance to travel. No legs poke out past the footprint of the roof. If you see a traveling hoist shadow but the whole thing stays inside a building outline, that's a bridge crane.

What a gantry crane looks like from the air

A gantry crane stands on its own legs, usually a pair of A-frames or box-section legs running down to wheels on a ground-level rail. It works outdoors, out in the open log deck, not tucked inside four walls. This is the giveaway from above: two parallel rail tracks running the length of a log pile, often somewhere in the 60 to 100 foot range apart, with the crane bridge spanning between them like a bridge over a creek. The crane itself usually sits mid-span, and at the right time of day you'll catch its shadow stretching clean across the logs below. Rail-mounted gantries built for log handling tend to be the single biggest piece of equipment in the yard, bigger than any stacker or front-end loader on site, so they show up even on a lower-resolution pass.

Straddle-type gantries complicate this a touch. They look similar from directly above but run on four separate leg clusters instead of two long continuous rails, more like a boxy spider straddling the deck than a bridge spanning a gap. Worth knowing the difference if you're trying to count equipment accurately rather than just confirm "yeah, there's a crane."

The quick tell: rail on the ground or rail on the wall

Trace the ground. If there's a visible rail running through open yard between rows of log decks, you're looking at a gantry. If the crane activity is boxed inside a roofline with no rail on open ground, it's a bridge crane working inside a building. That one distinction gets you most of the way there on any pass.

One wrinkle worth flagging: plenty of yards run both. A bridge crane handling the covered deck next to the mill, a gantry working the open storage yard out back for log sort and loadout. Don't assume a site only has one crane type just because the first thing you spot fits one category.

Why this matters for reading a yard without a site visit

Getting crane type right matters because crane count and crane size are two of the clearest signals a yard is running at capacity, or outgrowing what it's got. A sawmill that just added a second gantry to its storage yard is telling you something about throughput before anyone picks up a phone. That's the whole premise behind the quarterly equipment counts we run at Timber Yard Equipment: track stackers, cranes, and loaders site by site, alongside a rough read on log deck volume, so a sales rep can see which yards are adding iron before the mill makes it official.

If you cover sawmill and timber yard accounts and want that kind of read on your territory, take a look at what Timber Yard Equipment puts together each quarter.