How to Make a Thermal Map of Your City in 7 Steps

Cities are getting hotter than ever. An easy way to encourage people to add more green space and white surface coatings is by showing them a thermal photograph of their neighborhood.

A high-resolution thermal image taken using a FLIR 8000 series camera

You’d think that it would be easy to get pictures of how hot cities get in summer. It’s not. While satellites, aircraft, and drones are taking all sorts of photographs of the Earth, the surface temperature of cities, otherwise known as long-wave thermal, hasn’t been getting enough attention.

Thermal photography of cities is important because cities are getting hotter than ever. Hot urban temperatures in summer cause demand on the electricity grid to double in some cities (such as NYC) because people turn on the AC — and AC gobbles energy. Excessive heat also leads to heat-related illnesses and even death. There’s even a direct correlation between temperature and violent crime — the reason being that heat causes people to get become more aggravated.

The green and orange image above is what a high-resolution thermal image looks like. The orange and red areas indicate hot surfaces like roofs and asphalt roads. The green areas show cool things, like grass and trees.

This image was a gift from Thomas Schmack, who works at a geo-mapping company in Santa Cruz, California. He’d done a recent flight survey of the area.

Can we use thermal satellites?

NASA does have one thermal satellite, but it’s terribly low resolution — one pixel on the image represents about 100 meters on the ground.

NASA has recently made exciting progress on thermal imaging from space. Its Jet Propulsion Lab recently placed a thermal sensor called EcoStress on the International Space Station. It has revealed the urban heat islands of cities around the world.

These maps of four European cities show ECOSTRESS surface temperature images acquired in the early mornings of June 27 and 28, 2019, during a heatwave. The images have been enhanced to delineate key features such as airports. Airports and city centers are hotter than surrounding regions because they have more surfaces that retain heat, such as asphalt and concrete. Credit: NASA/JPL-Caltech

But there’s a catch to measuring thermal data from space. The wavelength of heat is so much longer than the wavelength of visible light, that by the time the electromagnetic waves make it all the way from Earth, through space, and up to the sensor on the space station, they get too blurry to make a high definition image.

There may be plans by satellite companies to launch new thermal satellites, but even if they do, we won’t be able to achieve the high resolution we’d like to see on the ground of being able to see a single tree or how one roof compares to another. You won’t be able to search a thermal satellite image for your local elementary school and see what surfaces are producing the most heat.

Can I use a drone?

Drones are good for capturing an aerial image of a small area such as school, campus, house, store, or office. You can attach a smaller FLIR camera to a drone and fly it around for 15 minutes to gather your image. You might be able to use the FLIR iPhone add-on for $399 on Amazon and attach it to a low-cost drone (If you do take any thermal images by drone, we’d love to see them!). However, if you want to capture an entire city, a drone does not compare to a planned flight by a light aircraft.

Good news is that creating a high-quality thermal map of your city with an aircraft need not be impossibly difficult or expensive. An aircraft can capture a small city in a few hours and cost under $1,000 per hour.

How thermal photography works

Thermal photography works just like regular photography, but it focuses on the long wavelengths that exist just outside the visible light spectrum. Infrared wavelengths consist of near-infrared, short-wave, medium-wave, long-wave, and far-infrared wave. The temperature range relevant to urban heat islands such as that of buildings, electronics, roads, cars, and human bodies is best represented by the long-wave band where the waves are in the range of 8–15 nanometers.

Diagram of the electromagnetic spectrum. Temperature is represented by longwave thermal in the Infrared range of the spectrum, to the right of the visible light spectrum.

How to make a thermal map of a city in 7 steps

1. Download a KML file of the area you want to photograph from Google Maps, Google Earth, or by googling “KML download {area name}”.
2. Chose the desired resolution of your thermal map in meters per pixel.
3. Make a flight plan using SkyIMD’s free flight plan software.
4. Acquire a high-resolution thermal camera, such as the FLIR 8000 series.
5. Hire a sturdy local aircraft that is or can be fitted with the camera attachment made by SkyIMD.
6. Wait until a clear hot day and fly!
7. Stich together the images using image stitching software.

Once you have the image, you can add a new thermal layer to our app, urbancanopy.io. Or if it sounds a bit tricky, sign up to urbancanopy.io and we can do it for you.