How often to resurvey a microwave hop for vegetation growth

Most operators don't have a resurvey policy for vegetation. They have a fault ticket policy. A hop runs fine for years, then a storm knocks a limb into the path, or a dry summer pushes a stand of poplar through the Fresnel zone, and the first anyone hears about it is a signal-quality alarm at the NOC. By then the crew is reacting, not planning.

The real resurvey interval for a given hop depends on what's growing under the path, how fast it grows, and how much clearance margin you built in at commissioning. Most networks don't have species-level canopy data for every hop, so they default to either "never" or "whenever someone complains." Neither is a resurvey interval. Here's how to set one.

What drives the interval

Three things determine how fast you need to look again: species mix, baseline clearance, and path length through canopy.

Fast growers like poplar, eucalyptus, and many pines can add well over a meter of height a year under good conditions. Oak, beech, and other hardwoods grow slower, often a fraction of that. If you don't know what's under a given span, assume the faster end and survey more often until you do know.

Baseline clearance matters just as much as growth rate. A hop with six meters of clearance over the canopy at the Fresnel boundary has years of runway before a fast grower closes the gap. A hop with a meter and a half of clearance might close it in a single growing season. Two hops with identical vegetation can need completely different cadences because one was engineered with margin and the other wasn't.

Path length through forest matters too. A hop that clips the edge of a tree line for 200 meters is a different risk than one that runs the length of a wooded valley for three kilometers. More canopy under the path means more places for one fast-growing outlier to matter.

Put together, a hop with slow-growing hardwood and generous clearance might genuinely be fine on a multi-year cycle. A hop with fast growers and tight clearance needs eyes on it every season, not every few years.

Why annual is the floor, not the answer

An annual pass is the cadence that catches encroachment while it's still a trim job instead of a fault. Growth happens over a season. A year-over-year canopy-height comparison against your clearance envelope gives you the lead time to schedule a crew before the next storm or dry spell pushes a borderline span over the line. Wait two or three years between looks and that lead time disappears. By the time you survey again, a hop that was six months from a problem is already a ticket.

That's the gap between a resurvey interval and a growth rate. Tree growth doesn't pause for your survey schedule. If your cadence is longer than the time it takes the fastest-growing species on your paths to close the gap, you're documenting vegetation after the fact rather than monitoring it.

The practical rule most RF planners land on: survey every hop at least once a year, and treat any span with less than a couple of meters of clearance, or known fast-growing species, as a candidate for a closer look between full passes. The annual pass keeps every hop on your radar. The judgment calls about which hops need more attention come from knowing your canopy, not from guessing at it.

If you're still setting that baseline from a spreadsheet of fault tickets and crew memory, an annual canopy-height check against your Fresnel clearance envelope turns that guesswork into a report you can actually schedule trims from, link by link.