Sequoia - Map your Fields, Capture the Invisible image description

 

 1. Sequoia RGB sensor reference dataset

Full dataset available to download on our support page HERE. The goal of this project is to get an othomosaic of a field using Sequoia’s RGB sensor.

 

 2. Sequoia multispectral sensors reference dataset

Full dataset available to download on our support page HERE. The goal of this project is to get an NDVI index map of a field using the Sequoia camera that captures Green, Red, Red edge and NIR wavelengths.

 

Platform: eBee (senseFly)

Average Ground Sampling distance: 10.66 cm / 4.19 in

Area covered: 0.2302 km2 / 23.0239 ha / 0.0889 sq. mi. / 59.9227 acres

 

 2. Is there a video tutorial for Sequoia? Pix4D Video Academy

 3. What’s Sequoia’s resolution/GSD for the multispectral cameras?

At 120m (400ft) Sequoia has a Ground Sampling Distance (GSD) of 11cm/pxl. In order to calculate the GSD at other flight altitudes please follow this link to our GSD calculator.

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4. Detailed Sensor Specifications

4 x monochrome sensors (global shutter)

  • Pixel size: 3.75 μm
  • Focal length: 3.98 mm
  • Resolution: 1280 x 960
  • Spectral band width:
    • Green: 530-570 nm
    • Red: 640-680 nm
    • Red Edge: 730-740 nm
    • Near Infrared: 770-810 nm

 

RGB sensor (rolling shutter)
– Pixel size: 1.34 μm
– Focal length: 4.88 mm
– Resolution: 4608×3456

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5. Tips for integrating Sequoia

Sequoia fits on a standard GoPro mount, use the default GoPro frame and clamp to about 1/3rd of the sensor in order to be able to attach the cables.
Provide 5V 2.4A power, or more, to the sensor, either via a compatible battery pack or from the drone’s battery through a 5V to 2.4A regulator.
Stick the irradiance sensor on top of the drone. The camera must be solidly connected to a structure with known geometry in order to leverage the information provided by the irradiance sensor and its IMU.
For eBee integration: senseFly has already developed an integration kit. Contact senseFly for more information on the product availability.

For 3DR Solo and DJI Phantom integration: Micasense is currently working on integration kits, contact them for more information on product availability.

More information about integrations with other drone manufacturers will be posted. Here an example of a 3D printable integration kit from one of our partners.

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6. How can I trigger the camera?

Sequoia hosts a Wi-Fi interface that can be connected to using any Wi-Fi capable device. Specify an image-triggering method for Sequoia by accessing a specific web URL (192.168.47.1) on any browser once your are connected to Sequoia’s Wi-Fi. Sequoia is also accessible through PTP/PTP-IP protocol via USB. This protocol enables access to many camera functions, including capture and trigger for automatic control with a flight planning software. Advance PTP protocol documentation here.
Pix4Dcapture will support Sequoia’s automatic triggering and is finalizing mobile app integration.

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7. What are the triggering modes available?

There are three image capture modes:

Time-lapse: The minimum values that can be set are: 0.5fps (frames per second) for the multispectral sensors and 1fps for the RGB sensor.

Distance trigger: The limits to the values that can be set are minimum 5m and maximum 1Km

Auto trigger: It captures images at the defined image overlap.

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8. Is it compatible with PixHawk?

Parrot has launched a crowdsourced project on DroneCode for the integration of Sequoia with PixHawk, for more information on the project click here.

 

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9. Can I fly under any light condition?

Yes, the irradiance sensor is designed to provide the information needed to correct for illumination differences. Results from Pix4Dmapper will be absolute and comparable under different light conditions: sunny or overcast. Note: as showed in the illustration below, flying under scattered clouds might lead to reflectance inaccuracies,  clouds may block sunlight heterogeneously across the field while the irradiance sensor can only capture one illumination condition per image.

 

 

10. Can I fly Sequoia without the irradiance sensor?

Yes, Sequoia can be flown without the irradiance sensor. However, in order to produce radiometrically accurate and absolute reflectance maps, a radiometric calibration target (a.k.a. reflectance target) would be required. For more information about reflectance targets click here.
Note: Sequoia can also be flown without the irradiance sensor and without  reflectance targets, but results will not be radiometrically calibrated and comparison between maps is not recommended.

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11. What else is included with Sequoia?

32GB SD card, three different irradiance sensor mounts, power and trigger connectors to interface between camera and irradiance sensor, a protection lens for the main camera body and a soft cloth to clean the lenses

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12. What Pix4D software version is best to process Sequoia images?

Sequoia imagery can be processed with Pix4Dmapper Ag,  Pix4Dmapper Pro and on the cloud. For a more detailed comparison of these two products, please click HERE. For information about the cloud, please click HERE.
Pix4Dmapper (2.1) processes the multispectral images using the camera rig constraints. This allows precise geometric reconstructions from the multispectral images, index maps can be created. From Pix4Dmapper 2.2 on, we also use the information coming from the irradiance sensor to normalize the reflectance maps according to the incident direct and diffuse sunlight.

The version for 2.2. is available HERE

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13. How should I fly Sequoia?

For optimal flight area coverage at a certain altitude you must allow for a time lapse between shots. To find out the minimum time to be respected depending on the flight height and speed, please refer to the following chart and diagram.

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Key:

In Red: the multispectral sensor and the RGB sensor cannot be activated
In Blue: the RGB sensor cannot be activated
In Green: all the sensors can be activated

To process Sequoia data, a minimum overlap between two successive pictures is needed. Refer to the diagram below to find out the distance between two shots depending on the Sequoia flight height for different overlap rate.

 

 

14. RGB sensor capabilities

The RGB sensor is mounted with a rolling shutter, while the multispectral sensors are mounted with a global shutter. This rolling shutter, together with the low and high frequency vibrations associated with the drone flight are still challenging our newly developed rolling shutter effect correction algorithm. For the moment, in order to generate orthomosaics with Sequoia, we recommend adjusting the flight speed to its minimum and to carefully stabilize the camera on the drone to reduce the rolling shutter effect.

 

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15. How to extract sensor data

The data can be extracted in three different ways: via USB, Wi-Fi and SD card.
Via USB
Use the micro USB cable (supplied) to connect the multispectral sensor to your computer.
In Windows: go to Start > Computer > Sequoia > Internal. This will take you to the multispectral sensor internal memory. You can retrieve the photos taken during the flight.
Note : Sequoia creates a folder for each sequence of shots. For example, if you have taken a single shot and then a shot in burst mode, you will have two different folders in Sequoia’s memory.

For Mac: open Image Transfer. This will take you to the multispectral sensor internal memory. You can retrieve the photos taken during the flight.
Via Wi-Fi
Connect the camera’s USB device port the drone or a USB battery. >Sequoia turns on automatically.
Make sure that the Wi-Fi appears in the list of available Wi-Fi connections. If not, press four times on the multispectral sensor button. >The multispectral sensor indicator light flashes blue when Wifi is enabled.
Connect your computer, tablet or smartphone to the Wi-Fi network: Sequoia_XXXX.
Open your internet browser and log in to the IP address 192.168.47.1.
Go to the Gallery tab and retrieve the photos taken during the flight.
Via SD CARD
Insert your SD card into your computer
Retrieve the photos taken during the flight.
You can also use the sunshine sensor as an SD card reader. To do this, connect the sensor’s micro USB device port to your computer.

Note: It is recommended to transfer the data to a computer after each flight.

 

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16. What’s the format of the output images?

Images are saved on the internal memory or on the SD card as a RAW 10-bit TIFF file for the 4 bands and as a JPG for RGB camera. It stores 5 images for each picture (one per band + RGB)

 

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 17. Future developments

Sequoia is a very advanced sensor, it provides an unprecedented amount of information. We are constantly working on new ways to leverage all that information to provide the most radiometrically accurate maps for agriculture: sun angle implementation, improved algorithms on the reflectance map generation, etc. With this constant development you can expect updates in our software that will translate into better leveraging of Sequoia’s information.

 

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