Utility vegetation management glossary

Resolução Normativa ANEEL nº 1.137/2025, published by Brazil's electricity regulator ANEEL in October 2025, sets obligations for distributors on resilience to extreme weather, including communication with public authorities, contingency plans and vegetation management. Distributors keep a vegetation management plan (Plano de Manejo Vegetal) that identifies priority areas and the criteria behind them, with minimum content set in PRODIST Module 6, and report the results in a separate annual report.

How GridGuardian measures it Span-level risk classes give the priority areas and the criteria in an exportable form; see the Portuguese guide to REN 1.137.

The band along a line, measured sideways from the conductors or the centreline, inside which vegetation is checked against the required clearance. Its width depends on voltage, line construction and local rules, and it is usually narrower than the full right-of-way.

How GridGuardian measures it The buffer width is a setting per voltage level or section, and every span is recalculated when you change it (adjustable zones).

In the Australian state of Victoria, electric line clearance is the legal duty to keep trees clear of power lines, set by sections 84 to 84D of the Electricity Safety Act 1998 and by the Electric Line Clearance Regulations, which contain the Code of Practice for Electric Line Clearance. Distribution businesses, councils and other responsible persons prepare Electric Line Clearance Management Plans, which Energy Safe Victoria (ESV) evaluates and audits.

How GridGuardian measures it Span-level clearance and fall-in results, with dated evidence from the FieldGuard field app, can support a management plan; the plan itself stays with the responsible person.

A raster in which each cell holds the height of the vegetation above the ground. It is computed as the surface model minus the terrain model (DSM minus DTM), usually from LiDAR or stereo imagery.

How GridGuardian measures it LiDAR and stereo give a CHM in metres where it is needed; across the whole network, our own neural network estimates vegetation height in bands from Sentinel-2, calibrated with LiDAR, not to the metre (LidarGuard).

The actual distance between vegetation and a conductor or other energised part, at a given moment and conductor position. It is compared with a required minimum, such as the MVCD or a distance set by local rules or the utility's own specification.

How GridGuardian measures it Clearance in metres comes from LiDAR or stereo imagery; satellite height bands only show where to measure (which method, when).

Completion evidence is the proof that a vegetation work item was done to specification: dated photos, location, crew, quantities and a check that the span now meets its clearance. Post-work verification is the independent check of that evidence, in the field or from new imagery.

How GridGuardian measures it FieldGuard crews close each item with photos and position, and the next usable satellite pass shows whether the span's risk class went down (post-work verification).

Sag is the vertical drop of a conductor between two supports; it increases as the conductor heats up under load and high air temperature, or carries ice. Blowout is the sideways swing of the conductor in wind. Both can bring the conductor closer to vegetation than its still, cool position, which is why FAC-003-5 requires transmission owners to account for conductor movement across the line's rated operating conditions.

How GridGuardian measures it LiDAR records the conductor only as it hung during the flight; the worst-case position has to be modelled from line and weather data, which a single survey cannot measure (LidarGuard).

The strip of land that contains a power line and its surroundings, used as the unit of planning and analysis. It is often wider than the legal right-of-way, so that trees outside the right-of-way that could reach the line are included.

How GridGuardian measures it GridGuardian analyses a wider strip along every line and splits it into a buffer zone and an environmental zone that you can resize (zones).

Cycle-based trimming revisits every section on a fixed calendar, regardless of how fast the vegetation grows there. Risk-based trimming orders the work by measured condition and consequence, so fast-growing or critical spans are cut sooner and quiet spans later.

How GridGuardian measures it Every span is ranked by exposure times hazard into a risk class, and the work list is sorted by it (risk classes).

A tree, inside or outside the right-of-way, that is tall enough and close enough to strike the line if it fell, whether or not it shows a defect. Usage differs between utilities, and some use the term interchangeably with hazard tree; the FAC-003-5 supplemental material mentions danger tree identification programmes for trees with the potential to fall near the line.

How GridGuardian measures it Tree height from LiDAR or stereo, set against the distance to the conductor, shows which trees are within reach (hazard tree detection).

A digital model of the network and its surroundings, such as poles, spans, conductors and vegetation, kept in step with field measurements. Its value depends on how often it is refreshed and how accurate its inputs are.

How GridGuardian measures it GridGuardian keeps one risk picture per span and pole, refreshed by satellite and updated with LiDAR, vehicle, drone and field data where they exist (the platform).

A digital surface model (DSM) records the height of the top surface, including trees and buildings; a digital terrain model (DTM) records the bare ground. The difference between the two is the canopy height model.

How GridGuardian measures it LiDAR gives both, because some pulses reach the ground through gaps in the canopy; stereo imagery gives a surface model and needs a separate terrain model under dense canopy.

Vegetation that has entered a distance or zone it should stay out of, such as the minimum clearance around a conductor or the buffer zone. In FAC-003-5 the term covers vegetation inside the MVCD, whether by growth, by a fall-in or by the line and vegetation blowing together.

How GridGuardian measures it Height bands and growth trends flag spans heading towards the limit, and LiDAR confirms the distance (encroachment detection).

The wider band outside the buffer zone where vegetation and land use still matter: trees tall enough to fall in, fire fuel, protected habitats and water. It is checked for fall-in and environmental constraints rather than for clearance.

How GridGuardian measures it Its width is a setting, like the buffer zone, and results update when you change it (zones).

The NERC reliability standard Transmission Vegetation Management, approved by FERC in March 2022. It applies to overhead transmission lines operated at 200 kV or higher and to certain lower-voltage lines identified as critical, and requires owners to prevent encroachment into the MVCD, document their vegetation maintenance strategies, inspect 100% of applicable lines at least once per calendar year with no more than 18 calendar months between inspections, and complete their annual work plan.

How GridGuardian measures it Dated, span-level inspection results, work items and completion evidence can be exported for audit through file, API or SAP PM; compliance itself stays the owner's responsibility.

Portuguese for the easement strip along a power line in Brazil: land over which the utility holds rights to build, operate and maintain the line, with restrictions on buildings and tall vegetation. Its width is set for each line in its project and legal documents.

How GridGuardian measures it The strip can be loaded as a zone, so vegetation inside and outside it is reported separately.

A vegetation risk where a tree or large branch, often from outside the cleared area, falls or leans onto the line, for example in wind, under snow or after root or stem failure. The test is whether the tree is tall enough to reach the conductor if it fell towards it.

How GridGuardian measures it LiDAR or stereo height plus the distance to the conductor gives each tree's reach; satellite height bands show where to measure first (hazard tree detection).

Hungarian for trimming: cutting back the branches of trees and shrubs near overhead lines to restore clearance. It is distinct from fakivágás (felling a whole tree) and from clearing scrub.

How GridGuardian measures it Trimming, felling and scrub clearing are recorded as separate work items per span in the FieldGuard field app.

A vegetation risk where trees or shrubs grow upward or sideways into the clearance around a conductor. It develops gradually, so it is managed by measuring height and growth rate and cutting before the clearance is lost.

How GridGuardian measures it Height band, vigour and growth trend are tracked per span in the buffer zone from Sentinel-2, with LiDAR for the exact distance (encroachment detection).

A tree with a defect, such as decay, dead wood, cracks, root damage or a strong lean, that makes it likely to fail, and that could strike the line when it does. A hazard assessment combines the likelihood of failure with what the tree would hit.

How GridGuardian measures it Height and distance come from LiDAR or stereo; defects such as a dead crown need high-resolution imagery or a field check (hazard tree detection).

A planned approach that combines several control methods, such as mechanical and manual cutting, selective herbicide use and encouraging low-growing plant cover, chosen per site by safety, cost and environmental effect. The FAC-003-5 supplemental material names ANSI A300 Part 7, the industry IVM standard for utility rights-of-way, as one approach commonly used by industry.

How GridGuardian measures it Regrowth after each intervention is measured per span, so the method mix can be judged by results (vegetation analysis).

Light detection and ranging: a laser scanner on a drone, helicopter, aircraft or vehicle that measures the distance to millions of points and builds a 3D point cloud. It gives tree heights and conductor-to-vegetation distances in metres, but only for the date of the survey and only where it was flown or driven.

How GridGuardian measures it LiDAR is used where the satellite flags risk; you can upload your own data or try samples in the LiDAR analysis tool (LidarGuard).

A workflow in which software marks likely objects or conditions, such as poles, defects or vegetation classes, and a qualified person checks, corrects or rejects each label before it is used. It speeds up review while a person stays responsible for the result.

How GridGuardian measures it In GridGuardian the machine pre-labels and an expert validates; you can try the image analysis in the machine vision demo (ImageGuard).

In NERC FAC-003-5, the calculated minimum distance between a conductor and vegetation that prevents flash-over, across the line's rated operating conditions. The values are listed in FAC-003 Table 2 by voltage and site altitude, and NERC notes that prudent practice keeps substantially greater distances at the time of vegetation work.

How GridGuardian measures it MVCD checks need distances in metres, which come from LiDAR; satellite height bands are not precise enough for them (LidarGuard).

The EU network of protected nature sites set up under the Birds and Habitats Directives. A plan or project likely to have a significant negative effect on a site goes through an assessment and permitting procedure, so vegetation work there may need permits, timing limits or specific methods.

How GridGuardian measures it Spans crossing Natura 2000 sites are flagged before work is scheduled (BioGuard).

The Normalised Difference Moisture Index, computed from near-infrared and short-wave infrared reflectance, tracks the water content of vegetation canopies. Values falling below the same place's seasonal normal can be an early signal of drying.

How GridGuardian measures it Canopy moisture is compared with each pixel's own normal for the same week in earlier years (drought and fire fuel).

The Normalised Difference Vegetation Index, (NIR minus red) divided by (NIR plus red), measures green, photosynthetically active vegetation. It shows where vegetation is and how vigorous it is, but not how tall it is.

How GridGuardian measures it Vigour and regrowth after cutting are tracked per span from Sentinel-2 (vegetation analysis).

The breeding period of birds, when cutting and felling can disturb or destroy nests. Many countries restrict vegetation work during it, with dates and rules that vary by country and species.

How GridGuardian measures it Work plans can be checked against nesting calendars before scheduling (BioGuard).

A tree standing outside the utility's right-of-way, where the utility may have limited rights to cut, but tall enough to reach the line. FAC-003-5 states the aim of minimising encroachments from vegetation located adjacent to the right-of-way, and work on these trees usually needs landowner contact or a permit.

How GridGuardian measures it The environmental zone covers the land beyond the right-of-way, so off-ROW trees within reach are listed per span.

Measuring 3D shape from overlapping photographs taken from different positions, by aircraft, drone, satellite or vehicle. It reconstructs visible surfaces well but cannot see the ground under dense canopy.

How GridGuardian measures it Drone photo surveys and stereo satellite pairs are processed this way (drone platform).

Portuguese for pruning. In Brazil, pruning of trees near urban distribution lines often involves both the municipality and the distributor, and ANEEL guidance expects formal instruments that set out who inspects, prunes, removes and replaces trees.

How GridGuardian measures it Pruning items are recorded per span with photos and position in the FieldGuard field app.

Labelling each point of a LiDAR or photogrammetric point cloud by what it hit: ground, vegetation, building, conductor, pole and so on. Clearance analysis depends on it, because conductor and vegetation points must be separated before distances are measured.

How GridGuardian measures it Classification, cleaning and clearance analysis are part of LiDAR processing (LidarGuard).

A temporary, planned shutoff of power to specific areas by a utility, used as a last resort when strong winds and similar conditions pose an imminent risk that its equipment could start a wildfire. The term is used in California, where the California Public Utilities Commission oversees it.

How GridGuardian measures it GridGuardian does not make shutoff decisions; span-level dryness and vegetation risk can be one input to them.

How often a satellite or constellation can image the same place. Usable observations are fewer than revisits, because clouds, haze and snow block optical images.

How GridGuardian measures it Sentinel-2 revisits every few days and cloudy passes are discarded; how often the risk picture is refreshed is a package setting (satellite vegetation management).

The strip of land along a line over which the utility holds legal rights, by ownership, easement or permit, to build, operate and maintain it, including vegetation control. Its width and the rights it carries differ by line, voltage and country.

How GridGuardian measures it The right-of-way can be loaded as its own zone, so vegetation inside and outside it is reported separately.

GridGuardian's four-level span risk class, from the product of exposure (how close the vegetation is, the voltage, what the span feeds) and hazard (growth rate, species, dryness, storm and fall-in potential). HC0 means no action, HC1 watch, HC2 plan and HC3 act now.

How GridGuardian measures it Each span's class updates as new passes arrive (how risk is ranked, live Atlas).

The System Average Interruption Duration Index: the total duration of sustained interruptions (longer than five minutes) experienced by the average customer over a period, usually a year. Utilities commonly calculate it following IEEE Std 1366 and report it with and without major event days.

How GridGuardian measures it GridGuardian does not calculate SAIDI; span risk lists can be exported and joined with your outage records.

The System Average Interruption Frequency Index: how often the average customer experiences a sustained interruption (longer than five minutes) over a period. Vegetation-caused faults that interrupt customers count in both SAIFI and SAIDI.

How GridGuardian measures it GridGuardian does not calculate SAIFI; span risk lists can be exported and joined with your outage records.

A European Copernicus satellite mission with a multispectral imager of 13 spectral bands and pixels down to 10 m. Its free, regular images of land and vegetation are widely used for vegetation indices and change monitoring.

How GridGuardian measures it The GridGuardian base layer is Sentinel-2 based and covers the whole network continuously; a 10 m pixel does not resolve single branches, so detail comes from LiDAR or high-resolution imagery (satellite vegetation management).

The section of an overhead line between two adjacent supports (poles or towers), including the conductors and the ground beneath. Many utilities plan and record vegetation work span by span.

How GridGuardian measures it Every result in GridGuardian is tied to a span and its two poles: one risk picture per span (the platform).

Two or three images of the same place taken from different angles, usually in one satellite pass, from which heights are computed by photogrammetry. High-resolution stereo gives a surface model and tree heights without a flight, but cloud, steep terrain and dense canopy limit it.

How GridGuardian measures it High-resolution stereo is bought for flagged sections through the data marketplace and processed; the imagery itself is not resold.

The survey after a storm that finds fallen or leaning trees, broken poles and downed conductors, ranks repairs and documents the damage. Speed and coverage matter most in the first hours, and detail matters later for repair planning and claims.

How GridGuardian measures it Before-and-after imagery, vehicle and drone surveys and field reports are compared span by span (storm damage assessment).

The planned interval between two vegetation maintenance visits on the same line section. In risk-based programmes the interval is set per span from measured growth and risk rather than as one value for the whole network.

How GridGuardian measures it Regrowth after cutting is measured per span, so the next visit is planned from measurement (regrowth).

A utility's documented approach to managing vegetation on its transmission lines, covering the maintenance strategy, work methods, inspection frequency and annual work plan. FAC-003-5 requires documented strategies of this kind and lists these elements in its supplemental material.

A measured drop in vegetation water content or vigour compared with the same place's normal for the season, from moisture indices, temperature and rainfall records. Dry vegetation burns more easily and drought-stressed trees can be more prone to failure, so dryness raises the hazard side of risk.

How GridGuardian measures it Canopy moisture against its own normal is reported as an early signal, not a forecast (drought and fire fuel).

Satellite or aerial imagery fine enough to show individual tree crowns, poles and buildings, typically with pixels of about half a metre or finer. It is bought per area and per date, so it is usually targeted rather than network-wide.

How GridGuardian measures it Imagery at 0.3–0.5 m is bought only where the satellite flags risk, through the data marketplace, and processed; the imagery itself is not resold.

Ground that stays saturated or under standing water for long periods. Along lines it blocks crew and vehicle access and stresses tree roots.

How GridGuardian measures it Standing water and waterlogged ground are flagged along the line (inland water and flooding).

A plan that documents the measures a utility proposes to reduce the risk of its equipment causing wildfires, such as vegetation management, inspections, grid hardening and operating practices. In California, utilities file them with the Office of Energy Infrastructure Safety, and the CPUC ratifies approved plans.

How GridGuardian measures it Span-level vegetation, dryness and completion records can feed the vegetation part of such a plan.

A bundle of vegetation work items, grouped by area, span list or contractor, issued to a crew with locations, quantities and specifications. It is the unit of planning, pricing and acceptance.

How GridGuardian measures it Ranked spans become work packages that go to crews in the offline FieldGuard field app.