Satellite Vegetation Monitoring for Electric Utilities: What It Can and Can't Do

Trees are a leading cause of outages on many utility systems. Patrols, helicopter surveys and LiDAR all work, but they can be expensive and slow, and they give you a snapshot. Satellite imagery is free, refreshed every few days, and covers a whole network at once. It can't do everything a survey does. Here is what it does well and where it stops.

How satellite vegetation monitoring works

• Imagery. Sentinel-2, a European Space Agency program, provides free 10 meter multispectral imagery and passes over the same ground about every 5 days.
• NDVI. The Normalized Difference Vegetation Index compares near-infrared light, which healthy plants reflect, with red light, which they absorb. Values run from -1 to +1. Higher means more green vegetation in that pixel.
• Ranking. LineGuard buffers your line by the corridor width you choose (the default is 15 m, about 50 ft, on each side), reads NDVI for each segment, and ranks segments against the rest of your network: the top 10% are High, the next 25% Medium, the rest Low. Because the ranking is relative, every network has a top group, even a well-maintained one. High-ranked segments within 500 m of each other are grouped into numbered work zones on a map, and an AI-written summary in the PDF explains the results in plain language.

Why utilities use it

• Speed. Upload a line file and get a ranked screening, work zones and a PDF in minutes for a small network. A full 500 miles takes longer.
• Frequency. Imagery refreshes about every five days, cloud permitting, and Professional has no cap on the number of reports. You can screen before a growing season, before you set a work plan, or any time you want a fresh dated record.
• Cost. Professional is $299 a month for up to 500 miles, about 60 cents a mile per month at the full 500. A screening does not replace LiDAR or patrols, because it measures neither height nor clearance. It helps you decide where to spend the patrol and survey money you already spend.

What NDVI can and can't tell you

• Higher NDVI means more green vegetation in the pixel. It does not tell you the vegetation is a tree, how tall it is, or how close it is to a conductor.
• Irrigated crops, lawns and pastures can read as high as trees. Roads, bare ground and water pull the number down, so a road running under a line can pull a segment's reading down.
• Comparing images from different dates can show where vegetation has changed. LineGuard screens one date per report today, and readings from different seasons should not be compared directly.

Where it fits with NERC FAC-003

FAC-003 applies to specific transmission lines: those at 200 kV and above, plus some lower-voltage lines that the Planning Coordinator or Transmission Planner has designated or that are part of a Major WECC Transfer Path. FAC-003-5 is the current version, and FAC-003-4 is the one before it. For lines in scope, R6 requires an annual Vegetation Inspection.

A LineGuard report can sit alongside your inspection records:

• A date-stamped screening record that states the imagery date and cloud cover
• Corridor widths you set
• Ranked segments and work zones to plan field inspections
• A PDF with the method, the rankings and a map

Whether a satellite screening satisfies R6 for a given line is up to the registered entity and its Regional Entity. It does not measure clearance distances. For lines outside FAC-003, such as most distribution, the same report is a maintenance planning record. See our FAC-003-4 and FAC-003-5 clearance guide and our 138 kV clearance guide.

Getting started

1. Upload a zipped shapefile, GeoJSON, KML or KMZ of your line network.
2. LineGuard picks a recent low-cloud Sentinel-2 image, reads NDVI along your corridor and ranks the segments.
3. Download the PDF, look at the work zones, and send crews to check the top ones.

The free plan covers up to 25 miles, one report every 30 days.

Satellite monitoring doesn't replace field crews

• Satellite gives a first pass. Crews confirm what is actually there.
• Instead of checking every mile first, crews can start with the highest-ranked work zones.
• Anything that needs a measurement, a species call or a height still needs someone on site or a survey.

Limitations

• 10 m pixels find stretches, not individual trees.
• No height and no clearance measurement.
• Rankings are relative to the network you upload.
• Clouds can delay a usable image, sometimes by weeks. Leaf-off and snow change the readings.
• Crops, lawns, roads, bare ground and water distort the reading.
• Your line data matters. A line drawn a few meters off will read differently.