Considerations for Conducting Separate IR and RGB Flights

 

 

Capturing RGB/IR imagery simultaneously with a dual payload is the preferred data capture method. However, it is possible to capture IR and RGB data in separate flights using different drones/sensors rather than using a single drone with a dual (IR/RGB) camera. Raptor Maps requires RGB and IR imagery (inspection level and obliques) to be captured on the same day. If a solar site is too large to capture in a single day, the pilot can break the site up into sections, ensuring that RGB and thermal imagery (including obliques) are captured on the same day for each section.

Altitude will need to be adjusted for each flight to capture the required Ground Sample Distance (GSD) given the specific sensor and inspection level of the flight. GSD requirements for thermal and RGB imagery for each inspection level are listed below. Thermal (IR) imagery must be RJPEG (the Zenmuse XT has an option for RJPEG and JPEG – ensure RJPEG is selected). RGB imagery must be JPEG. All imagery must contain metadata (GPS, relative altitude, gimbal altitude, and timestamp).

 

Thermal Imagery

Type of Inspection

Description
Smallest Visible Features
Ground Sample Distance
Maximum Speed

Raptor Overview

Ideal for rapid drone flights and string-level outages
Module
15.0 ± 5.0 cm/pixel
30 mph

Raptor Standard

Ideal for annual preventative maintenance
Diode, Hot Spot, and Cell
5.5 ± 0.5 cm/pixel
12 mph

Raptor Comprehensive

IEC TS 62446-3 thermography standards for Absolute Temperature Accuracy
Diode, Hot Spot, and Cell
3.0 ± 0.5 cm/pixel
7 mph

Supported Drones and Thermal (IR) Sensors

Make

DJI
DJI
DJI
DJI
DJI
DJI

Model

M200
M210
M210 RTK
M200 V2
M600
Inspire 1

Sensor

XT
XT
XT
XT
XT
XT

M210 Compatibility

If using the DJI M210 (or M210 RTK) dual gimbal with separate IR/RGB sensors, DJI Ground Station Pro will only capture imagery from slot 1. GS Pro will not simultaneously capture imagery from sensors in slot 1 and 2. The pilot will have to conduct separate IR/RGB flights and ensure the sensor is mounted in slot 1 for each flight. The following image shows where slot 1 and slot 2 are labeled on the M210 dual gimbal mount.

Visible (RGB) Imagery

Type of Inspection

Description
Smallest Visible Features
Ground Sample Distance

Raptor Overview

Ideal for rapid drone flights and string-level outages
Module
5.0 ± 1.0 cm/pixel

Raptor Standard

Ideal for annual preventative maintenance
Cell
2.0 ± 1.0 cm/pixel

Raptor Comprehensive

IEC TS 62446-3 thermography standards for Absolute Temperature Accuracy
Sub-cell
1.0 ± 0.5 cm/pixel

Supported Drones & RGB Cameras

Make

DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
DJI
Parrot
Parrot
Autel
Autel
Autel
Skydio

Model

Phantom 4
Phantom 4 Pro
Phantom 4 Pro V2
Phantom 4 RTK
Inspire 1
Inspire 2
M200
M210 RTK
M200 V2
M200 RTK V2
M300
Mavic
Mavic 2 Pro
Mavic 2 Enterprise
Air 2S
ANAFI
ANAFI USA
Evo II
Evo II Pro
Evo II RTK
X2

Sensor

Built-In
Built-In
Built-In
Built-In
Zenmuse X3, Zenmuse X5
Zenmuse X4S, Zenmuse X5S with 15mm DJI lens
Zenmuse X4S, Zenmuse X5S with 15mm DJI lens
Zenmuse X4S, Zenmuse X5S with 15mm DJI lens
Zenmuse X4S, Zenmuse X5S with 15mm DJI lens
Zenmuse X4S, Zenmuse X5S with 15mm DJI lens
P1
Built-In
Built-In
Built-In
Built-In
Built-In
Built-In
Built-In
Built-In
Built-In
Built-In

Calculating GSD or Flight Altitude from GSD

To calculate GSD or calculate altitude to obtain a certain GSD, you will need to know the following variables.

Sensor height (millimeters)
Sensor width (millimeters)
Image height (pixels)
Image width (pixels)
Focal length of the sensor (millimeters)
Flight altitude (centimeters) – if calculating GSD
GSD (cm/pixel) If calculating altitude for a given GSD

GSD Equations:

GSDh = flight altitude x sensor height / focal length x image height
GSDw = flight altitude x sensor width / focal length x image width

Whichever value is larger (GSD height or width) will be the functional GSD to account for the “worse” resolution of the two.

GSD Calculators

There are several open-source GSD calculators which allow you to select from a preset list of drones/payloads or manually enter the variables necessary to calculate GSD. Here is a non-exhaustive list of GSD Calculators:

Propeller
Handal Selaras
HeliGuy
Pix4D (Downloadable .xlsx/.ods format)