---
title: Heatmap of Range and Doppler Made Visible with Fast Fourier Transform (FFT) (Video)
description: The following video visualizes the Doppler frequencies of a person approaching and moving away from the radar source. We use Fast Fourier Transform in FreeScopes Basic II.
---

[SkyRadar Blog | Radar Training Systems Online Radars - SkyRadar ](https://www.skyradar.com/blog)

# [Heatmap of Range and Doppler Made Visible with Fast Fourier Transform (FFT) (Video)](https://www.skyradar.com/blog/heatmap-of-range-and-doppler-made-visible-with-fast-fourier-transform-fft-video)

 Written by [Ulrich Scholten, PhD](https://www.skyradar.com/blog/author/ulrich-scholten-phd) | Dec 20, 2021

The following video visualizes the Doppler frequencies of a person approaching and moving away from the radar source. We apply Fast Fourier Transform.

In the B-Scope, we can visualize a heatmap of range and Doppler.

The horizontal line in the center of the B-Scope is the "zero-speed"-line. Dots above the line indicate positive speed, meaning an approaching movement. Dots below the zero-speed line indicate distancing movements. The x-axis represents the distance from the radar source.

<https://www.skyradar.com/hubfs/Images/Blogs/Range-Doppler-Heatmap.png>

The signal is analyzed with the help of the Burst block and the FFT block. Both are part of [FreeScopes Basic II](https://www.skyradar.com/en/8ghz-radar-training-system/freescopes-basic-ii-description).

[View full post](https://www.skyradar.com/blog/heatmap-of-range-and-doppler-made-visible-with-fast-fourier-transform-fft-video)

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