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How to Calculate the Optimal Flight Speed in Drone Missions?

Updated: Aug 23, 2022

Overview

With any drone mission, one of the parameters to carefully calculate is the flight speed.

A carefully calculated flight speed will help your drone fly fast enough to be efficient and also slow enough so that the data collected is of high quality.

But what parameters do we need to consider whilst calculating the drone speed?

And what formula should we use to calculate it?

We will explore these questions in the sections below.

Goals

As with any drone flight, calculating the flight speed starts with identifying your end goal or deliverable. Does this mission need the highest quality data or is this mission simply one of many missions to be flown on the same day?

If your goal is the former you will err towards flying slower and if your goal is the latter, you will probably prefer flying faster. But how do we calculate the perfect flight speed that strikes the right balance between the two?

Factors

So, how do you calculate the correct flight speed for your drone?

Typically, there are 3 main factors at play:

1. Lighting Conditions

The lighting conditions on site on flight day dictate the exposure settings for your drone. On a bright day, you will want your camera to have less exposure to light and on a dull day, you would want this to be the opposite. These settings therefore in turn affect the shutter speed (an exposure setting) for the drone's camera. The shutter speed is the speed at which the drone's camera can take a single image at a time, and is measured in the format 1/6000.

Lighting conditions affect exposure settings and shutter speed

2. Image Overlap / Interval

Every drone mission you fly typically involve taking images at a set interval (every few seconds or every few metres travelled by the drone). If you are flying for mapping or inspection purposes, this image interval will be defined by the amount of overlap in your images. This interval is an important consideration in the flight speed as you do not want to fly faster than the camera's capability to take pictures at this interval.

Intuitively, you can think of this as the drone and the camera having different speeds and if the drone is flying too fast, the camera might not be able to keep up due to its inherent camera speed.

3. Camera Photo Interval

The third factor affecting the drone's flight speed is the drone camera's Photo Interval. Every camera has an inherent photo capture interval (The time is takes for the camera to write the image to the SD card). During this photo capture interval, the camera is unavailable and is unable to take further images. Again, if the drone is flying too fast, it would mean that the camera is unable to keep up with the photos and some images will be lost during flight, which is a complete no-no if your goal is high quality data!

Most DJI cameras have an interval of 2s when captured JPEGs and an interval of up to 10s when capturing in RAW+JPEGs mode.

Calculation

Putting together the factors mentioned above, the drone flight's speed is simply the Image Interval Distance (in m) divided by the Camera Interval. It is important to note that the Camera Interval should be the maximum of the shutter interval (dependent on lighting conditions) and camera's inherent photo interval.

```
Optimal Flight Speed = Image Interval (m) / Camera Interval (s),

where Camera Interval = max (Shutter Interval, Photo Interval)```

And there you go, that's how you can calculate the optimal flight speed for you mission.

Want to calculate this for yourself? Get our free and comprehensive spreadsheet designed with Drone Mapping and Inspection formulas over here

Tools

Even though you might able to calculate the optimal flight speed, the key question is - should you? Using tools such as Hammer Missions for drone mission planning, an optimal flight speed is automatically calculated for you using all the parameters mentioned above. Tools help us build efficiency in our operations, but as with any process, it's good to understand the math behind the scenes as it only helps us use the tool with confidence and more efficiently.

Summary

In this guide we looked at how to calculate the optimal flight speed for your drone mission.

If you haven't got a Hammer account as yet, and would like try Hammer Missions you can get started on our free trial.

We look forward to hearing from you.

- The Hammer Team

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