SKYDOG ATI LLC
Professional Drone Thermal Imaging & SAR Services in New England.
Lessons from the Field: A SAR Drone Pilot’s Notebook
A Reflection on Search & Rescue Operations
Jenness Keller
FAA Part 107
Infrared Thermographer Level 1
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When I first started flying drones for Search and Rescue (SAR), I thought technology would do all the work. I was wrong. The years since have been a humbling education, taught not just by successful finds, but by the "empty" missions and the feedback from more experienced pilots. What follows is not a rulebook, but a collection of lessons learned—scars and successes—shared in the hopes that they shorten your learning curve.
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Note: This covers active Search operations only. It does not cover Search and Recovery operations, which typically utilize different mapping technologies and specialized SAR software.
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1. Equipment: Understanding Our Eyes in the Sky
Most of us are flying with the industry standard: uncooled microbolometers with a 640 x 512 resolution (like those on the Matrice 4 Thermal or Matrice 30T). These operate in the Long Wave Infrared (LWIR) spectrum.
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The Reality of LWIR
Working with military tech as a software engineer, I’ve learned to respect what we have. LWIR is excellent for detecting body heat against a cool background, but it has distinct limitations. Unlike Short Wave IR (SWIR), which handles moisture and atmospheric haze better, LWIR struggles with humidity. Water vapor absorbs LWIR energy, meaning on a super humid night or in dense fog, your range is drastically cut.
Furthermore, uncooled sensors are susceptible to "thermal drift." If you fly hard and the drone heats up, the sensor can get noisy. I’ve learned to let the drone acclimate to the outside temperature for a few minutes before launching critical searches.
Frequently use the FFC (Flat Field Correction) option on the pilot screen. It recalibrates the microbolometer to correct for thermal drift and non-uniformity noise.
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2. Pre-Mission Prep: The Flight Before the Flight
Spend 10 minutes on the ground to save 30 minutes in the air.
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Airspace Safety: My first check is always airspace. I use AirHub Portal or Air Control on my phone for immediate situational awareness. If I'm at my PC planning a mission, I consult the FAA UAS Facility Maps to check grid restrictions.
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Topography & The "Local" Factor: Maps don’t tell the whole story. I look for natural barriers (bodies of water, cliffs) that would funnel or draw a lost subject. I assess the tree mix—evergreens are thermal blockers, while hardwoods in winter are transparent. This also is when to look for possible launch sites. Elevation readings are a good starting point, then on-site visits will be the deciding factor.
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Launch Sites: Always check online maps (Google Maps, OnX, Google Earth) and also ask local experts or the incident commander for the best high ground. A launch site 50 feet higher can mean maintaining connection behind a ridgeline. Using a repeater, like the DJI D-RTK 3, can also have an excellent impact on signal range at challenging launch sites (3000' to RC and 15 mile range for drone).
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Inform Stake Holders: In most cases, it's a good idea to inform the police, especially for night operations. They've always appreciated being made aware and at times are needed. Especially if near any roads, private property etc. Also, schools or landowners if on their property.
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3. Lost Animal Behavior: Psychology Over Technology
Finding a lost animal isn't just about looking; it's about thinking like them.
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Fight or Flight: Most lost animals are in survival mode. They don't just wander; they react.
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Dogs: When lost, dogs often revert to feral instincts. They may not respond to their name and might actually flee from searchers or owners. They tend to follow the path of least resistance but will hunker down in deep brush if injured or terrified. See Fight or Flight.
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Horses: As prey animals, they seek open spaces where they can see threats, or they herd up. They are surprisingly calm but will drift toward grazing areas.
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Cattle: They follow the herd and water. If a cow is alone, it is likely sick, injured, or stuck.
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Migration: Almost all animals eventually prioritize safety, water, and food (in that order). I always check water sources first.
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4. Seasons and Canopy Impact
Seasons dictate tactics. In summer, the "thermal clutter" is high; rocks and trees hold heat late into the night. In winter, the background is cold, making living things pop, but sunny days will still warm up exposed rocks and trees.
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Dealing with Sun (The Enemy of Thermal): On sunny days, rocks and stumps heat up to body temperature. This is where the IR Pallet IronRed or DJI "Inspection View" (or similar high-contrast modes) becomes vital. DJI "Inspection View" will narrow the temperature span (Isotherms), One can filter out the ground clutter, improving isolating to biological targets. Also planning Dawn, Dusk or night flights will help. If the need to fly on a sunny day, arriving a few hours before dusk can work out, since the sun is especially low already. Allows concentrating missions of Eastward/Northernly facing hillsides etc.
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5. Weather Impact
Weather is the filter through which we see the world.
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Fog: The enemy of LWIR. It acts like a wall. If I can't see 100 yards with my eyes, the thermal likely can't either. Tree-top flights are required.
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Icing Conditions: If the temperatures are close to freezing (above or below), with low cloud cover, icing can stop flights.
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Full Sun: This is worse in warmer seasons, since there are more objects exposed to heat up.
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Full Cloud Coverage: Actually my favorite condition. Clouds block the sun from heating the ground, creating a uniform, cool background. This also applies to dawn and night searches.
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Smoke: LWIR penetrates smoke much better than visible light, but heavy particulates (carbon) will still scatter the signal. SWIR is better here, but LWIR is still a potent tool for fire SAR.
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Warm vs. Cold: Detection is all about Delta T (difference in temperature). Uncooled microbolometers detect relative temperatures.
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Limitation: The sensor struggles with the thermal mass of a cooler temperature next to a smaller object with a higher thermal signature. Distance to the object is a significant factor here. For example, if standing near an engine in nadir mode: the top of your head may be 90°F, but if a truck is near you (even 20’ away), the truck will "pop" more than you, especially from 100’ or higher.
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6. Gimbal Angle: The Geometry of Detection
I used to fly strictly top-down (nadir), but reading a Norwegian SAR research paper (In-Depth Analysis: Norwegian Police Drone Search Techniques in SAR Operations) adjusted my approach.
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Key Recommendation: The "70 Degree" Rule
The research argues against the traditional "lawnmower" mapping angle of 90° for search missions. Instead, it recommends an oblique angle (typically around 70° down) for the following reasons:
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Side-Profile Visibility: A 90° view often fails to detect people because it only shows the top of the head/shoulders, which blends into the terrain. A 70° angle captures the "side" profile of a body, which is easier for the human eye and AI to detect.
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Tree Canopy Penetration: A straight-down view is blocked by tree branches. An angled view allows the camera to see under the edges of tree canopies.
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Context: It provides enough context to identify objects while maintaining a high enough ground sampling distance (resolution).
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My Approach:
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90° (Straight Down): Highest emissivity (accuracy) and best for mapping. It is usually the best angle once a target is located or in the process of recovery. However, it offers the smallest thermal footprint.
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70° (The Sweet Spot): The Norwegian SAR study changed how I fly. This angle allows you to see the side profile of a standing person or animal, offering a larger thermal target. It optimizes coverage width while maintaining good signal.
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55° (Reaching Out): I use this for "pivots" (scanning). It lets me look far ahead. The terrain needs to support this (e.g., bogs, fields, winter hardwoods). The trade-off is low thermal accuracy; thermal signatures will look cooler than they are, but a solid shape that looks out of place can be your target.
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Success Story: One horse and two dogs were found recently this way. All were in the woods, at the far end of a flight.
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Technique: Try to never lock the gimbal. Constantly tilting helps you see through gaps in the trees and under canopies.
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7. Altitude: Finding the Balance
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300’ AGL: My standard patrol altitude for large open fields. It provides a wide field of view.
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150’ (or Tree Top): Essential for difficult conditions (dense canopy, summer heat). In heavy woods, I have to be low enough to look between the branches, not just at them.
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Laser Ranger Finder: This can be a drone saver if in hilly terrain. Even if looking out at 70 degrees, this range will save flying into a tree, if you keep it at a safe range. Since the collission avoidence is disabled at night, this is a huge help.
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8. Grid vs. Freelance Missions
There is a time for rigid discipline and a time for intuition.
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Freelance (Hasty Search): When I first arrive, I often fly "freelance" to hit high-probability Points of Interest (POIs)—the last known point, nearby water, or trails. Performing ‘pivots’ at those areas can pay off. It’s fast and covers the "obvious" spots.
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Grid (Methodical): If the hasty search fails, I switch to a grid. It ensures 100% coverage.
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Hybrid : I often combine them. I will fly a grid line, but when the drone reaches the end of a leg, I stop and perform a Pivot.
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The Pivot: I spin the drone 360 degrees while tilting the gimbal between 55° and 70°. This allows me to look "deep" into the woods surrounding the grid before turning back for the next leg.
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9. DJI IR Palettes: Painting the Heat
Color is subjective, but over time, I’ve settled on a hierarchy of utility:
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Tint: My go-to. It uses a high-contrast grayscale for the background but highlights the hottest pixels in red/orange. It screams for attention when something hot enters the frame.
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Black Hot: The "Hunter's Palette." To the human eye, spotting a dark black dot moving against a gray background is often easier than spotting white-on-gray. It feels more natural for tracking motion.
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White Hot: The standard. Good for urban areas, but I find it causes more eye fatigue at night than Black Hot.
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IronRed: Good for for extreme heat differences (like a fire) or a warm sunny day.
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10. Remote Controller Pilot Tools
Min/Max Temperature Window: The thermal interface has a great feature: the Min/Max Temperature Window.
On the touchscreen, dragging a finger from the top-left to the bottom-right of the screen draws an adjustable box. The drone will then analyze only the area inside that box, showing the hottest and coldest points relative to that specific area.
This is great for challenging conditions, such as snow-covered ground on a cloudy day with many small areas of exposed water. In Tint mode, since everything is relative, the water might normally show up as pink (near the hot end of the spectrum) because it is in the warmer range from all else. i.e ~30 degrees (it's moving). By using the box tool, you can isolate specific areas to eliminate these false positives—just remember to account for altitude, gimbal angle, target size, proximity to large mass thermal signatures, target insulation (e.g., a thick-coated Husky vs. a Boxer), and the health of the subject. I.e. A dog may show as 35 degrees (like a Boxer) where it is many times warmer than that. If the dog is a Husky, many times harder to spot.
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SBS (Side By Side) Mode: This mode allows two views to be shown on the screen. Typically, the elft side would be IR and the right side, zoom. The DJI Matrice 4T allows configuring all cameras, including the collision avoidance cameras.
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Final Thought
The drone is just a tool and this is one opinion. Everyone has their technique and preferences. The real sensor is the pilot. Stay humble, trust your gut, verify with your screen, and never stop learning from the pilots who flew before you. Safe flying.
Sources
In-Depth Analysis: Norwegian Police Drone Search Techniques in SAR Operations (PDF)
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A Guide Comparing DJI Mavic 3 Enterprise, Thermal & Multispectral. - Prisma Technologies
Uncooled VOx Microbolometer. Refresh Rate: 30Hz. NETD: ≤ 50mk@F1.0. Resolution: 640x512@30fps.