MAIA M2 is the new lightest modular multispectral camera

The potential offered by RPAS (Remotely Piloted Aircraft Systems) in environmental prevention and monitoring is related to the possibility for sensors to fly over areas of interest. In the last decade proximal sensing technology saw a great development both with regard to sensors (lightweight multispectral and iperspectral sensors) and platforms (aircraft, helicopters, RPAS).

Research and development in photogrammetric and multispectral surveys is offering new innovative solutions in sensors and technologies to monitor our environmental resources with very high frequency, precision and reliability.

MAIA is the most advanced multispectral camera designed to be employed onboard UAV systems, airplanes and terrestrial rovers as well, jointly developed and made in Italy by SAL Engineering, that designs and manufactures systems for data acquisition in sea, air, land environments, EOPTIS, specialized in designing and manufacturing opto-electronic measurement instruments, and 3DOM Research Unit of Fondazione Bruno Kessler, that is actively involved in accurate measurements and reality-based 3D reconstruction issues. In this team the Italian excellence in the fields of physics, optics, geomatics, 3D modeling and remote sensing have been concentrated: a consolidated know-how was made available for the construction of a multispectral imagery acquisition instrument that could ensure scientific rigor and total control of geometrical and radiometric data for a correct multispectral survey.

Regarding the differentiation of wavelenght intervals along the electromagnetic spectrum, MAIA has been designed according to two main sets: MAIA WV and MAIA S2. Nevertheless, thanks to the profitable collaboration with agronomic consulting companies and environmental protection agencies, or with universities and research institutes, a fully customizable modular solution was subsequently developed.

MAIA M2, in fact, is the new modular multispectral camera that the user can customize with a large portfolio of VIS-NIR bandpass filters, according to his needs. The MAIA M2 single module can be composed using a pair of available band-pass filters. The choice of the pre-selected filter pairs will be made according to the most widely used multispectral indexes with two single bands, or on the basis of the aim of the multispectral survey. In the following table you can see the selected filters that are available in stock:

Each module has stand-alone capability with external trigger and strobe or free run mode, and presents several inputs/outputs for external devices interfacing such as trigger, strobe, serial port, USB and two aux port. The module/camera is based on a double global shutter CMOS sensor with 8/12 bits resolution and automatic exposure with selectable target value.

Single module of MAIA M2 has the lowest values in the market of modular multispectral cameras in terms of size (48 mm X 33 mm X 23 mm), weight (70 g) and price (1990 € until July 15th), but it presents the highest values in terms of resolution and sensitivity of sensors.

Multi-module management, up to 8 modules, is possible using the external MAIA M2 Control Unit that manages the images synchronization and geo-referencing, the powering of modules, the reading of PWM inputs, the light sensor input, two outputs with customizable variable advance for delay compensation of any connected DSLR cameras. An RTK version of MAIA M2 Control Unit is supplied including the GNSS antenna, the UHF antenna, the Lux Sensor and the connection cables for batteries, PWM inputs and DSLR shutter input. Multispectral raw images and parameters are stored in a removable SD card, and they can be downloaded from USB in order to be pre-processed with MultiCam Stitcher Pro, the MAIA images pre-processing software.


The following table shows some combinations of 2 or more MAIA M2 modules, useful to allow the calculation of many of the main multispectral indexes:

MAIA is basically the proper instrument for your multispectral survey.

You can detect VIS-NIR informations through 9 global shutter sensors with high resolution and top sensitivity; next, you have the total control on creating your dataset of undistorted and geometrically corrected images for reflectance analysis, indexes calculation and photogrammetric processing. You can then make decisions on monitoring crops, wineyards, forests and coastal environments, in order to safeguard ecosystems and to make your agronomic system more efficient. Along with the camera, an image processing software will be provided for correction of geometric and radial distorsion, for coregistration (pixel-pixel convergence) of RAW multispectral images acquired with MAIA, with tools for indexes calculation and for band combinations.

Since its foundation, SAL Engineering has participated, contributing with the design and management of data acquisition, synchronization and processing systems, to several projects with agronomic and precision farming companies, or environmental protection agencies that deal with natural environments such as coastal dunes, forests, reclaimed sites, areas with high environmental risk.

With the acquired know-how, the company has then decided to develop its multispectral data acquisition system in compliance with the requirements of the various interlocutors over the years, whether they are environmental protection agencies, whether they are farmers, vine growers, agronomists, experts in natural and forest sciences.

MAIA is designed to be employed on board UAV systems or on board aircrafts, and it finds several applications on board terrestrial rovers for precision agriculture, geophysics, environmental monitoring. Main applications of the multispectral survey conducted with MAIA concern the following fields of interest:

  • Agriculture and terrain survey: precision agriculture, detailed study of satellite imagery, vegetation indexes mapping, plant species recognition and biomass mapping, monitoring of health conditions of crops and plants;

  • Geology: detection of paleochannels, detection of typology of soils, geological characterization and mapping, classification of composition of soils, characterization of materials in landslides and floodings

  • Industry: detection of chemical dumpings, monitoring of industrial plants, monitoring of leachate in landfills, detection of non-authorized dumps, detection and classification of materials in terrains and structures;

  • Environmental monitoring: detection of pollutant spilling and waste recognition, classification of terrains and chemical-physical characterization, analysis of spills in rivers and coastal environments.

CMOS sensors settled in MAIA have resolution of 1.2 Mpixel each, and present excellent characteristics in terms of sensitivity. Each sensor is global shutter and shoot simultaneously: it follows that it is not necessary to stabilize the shot with gimbal, which is indispensable with roling shutter sensors to avoid distorsions, crawling and blurring pixels in the images. The high quality and the radiometric validity of data obtained with MAIA are then guaranteed even during high speed flights.

Thanks to a web panel easily accessible through Wifi and Ethernet, MAIA permits a fine regulation of all parameters concerning the acquisition activities, from exposure time of each sensor to shot frequency. Automatic configurations are available for standard operations.

MAIA WV is based on an array of 9 sensors with the following characteristics:

  • RGB sensor (RBG Bayer pattern)

  • 8 mono-chromatic sensors with sensitivity in VIS-NIR range from 390 nm to 950 nm

Mono-chromatic sensors are matched with bandpass filters based on the intervals as follows:

MAIA S2 is based on an array of 9 monochromatic sensors with sensitivity in VIS-NIR range from 433 nm to 899.5 nm, that are matched with bandpass filters as follows:

MAIA can interface with various devices that can integrate embedded data into the images:

  • GNSS receiver to geotag images

  • radio transmitter that send images to the operator and give him feedback about mission and data acquisition

  • radio receiver for radio remote control of the camera

  • connector for gimbal stabiliser, that takes advantage of the IMU onboard, keeping bearing and orientation

  • other devices that need signal at the moment of the shot

  • ILS – Incident Light Sensor, developed by SAL Engineering and EOPTIS

The Incident Light Sensor integrated with MAIA measures the level of the ambient light for each shot in each band during the multispectral survey. It allows the correction for downwelling light changes during the flight, such as those caused by clouds covering, and calculate the true reflectance ratios for the correct index calculations. A high precision GNSS version with RTK is available, which allows a centimeter-level positioning accuracy. MAIA WV and MAIA S2 can be equipped with ILS for the radiometric correction of each single shot in each single band, for the best multispectral data acquisition, in order to:

  • determine precisely the fertilization by identifying the symptoms of nutritional deficiencies;

  • optimize the contribution of pesticides through the early identification of biotic stress;

  • optimize irrigation of crops by identifying areas of potential water stress;

  • calculate agronomic indices, and set a monitoring plan in order to preview the yeld of crops;

  • monitor dumps, water bodies, terrains, mines, soils and forests with a correct radiometric information, to create an effective monitoring plan of interventions.

Each sensor has 1280×960 pixels and the dimension of each pixel is 3.75 μm x 3.75 μm. Each sensor has fixed focus lens with the following characteristics:

  • Nominal focal lenght: 7.5 mm

  • Aperture f/#2.8

  • FOV 35° HFOV; 26° VFOV 43° DFOV

Lens are adjusted with focus in laboratory, with no possibility of intervention by the user. In MAIA WV, S2 and M2, lenses are calibrated in laboratory. Each optics of every produced MAIA is calibrated in laboratory and for each camera the Calibration Certificate is available, with the following parameters:

  • calibrated Focal Length

  • position of Principal Point

  • lens distorsion parameters

Calibration and certificate is carried out by 3DOM in their laboratories.

For the survey operations, the Ground Sample Distance (GSD) and the Field of View (FOV), depending on the Altitude above Ground Level (AGL), are shown in the following table, that also shows the available max speed of the aircraft to acquire images with no motion blur, considering an acceptable pixel blurring and crawling lower than the size of the pixel. The maximum speed of the aircraft depends on images overlap and on shot frequency.

AGL
(m)

GSD
(mm/pixel)

FOV
(m
2)

Max flight speed

with 10 ms exposure time

(m/s) – (km/h)

Max flight speed

with 1 ms exposure time

(m/s) – (km/h)

50

23

30 x 23

2.3 – 8.4

23 – 84

75

35

45 x 34

3.5 – 12.7

35 – 127

100

47

60 x 45

4.7 – 16.9

47 – 169

150

70

90 x 68

7.0 – 25.3

70 – 253

200

94

120 x 90

9.4 – 33.8

94 – 338

300

141

180 x 135

14.1 – 50.6

141 – 506

400

188

240 x 180

18.8 – 67.5

188 – 675

Via Wifi or via GigaEthernet port, users can interface with MAIA to configure parameters, to visualize in real-time images during the acquisition and to download the already saved ones. For these purposes there are several interfaces: a keyboard, a powerful web panel, two inputs for radiolink receivers. Web access is available both through a high-speed GigaEthernet connection, and through Wifi connection for operation directly on the field.

Images are stored in an internal SSD solid memory that is mechanics-free, then it guarantees long term high reliability. Memory capacity can guarantee more than 10000 images. RAW files until 12 bit, that concentrate a large quantity of information, are supported.

Thanks to MAIA MultiCam Stitcher Pro software, you could create multi-layer tiffs and multichannel tiffs, you can create views with combination of bands, index images and previews of the images just taken. You can correct the geometrical distortion of images, get the coregistration pixel-pixel for each band and correct the radiometrical informations within the pixels. Thanks to this software, you can generate the specific kind of dataset that could be useful for your purpose: photogrammetric processing, single shot analysis, indexes or band combination mapping. This image processing software is jointly developed with the cooperation of 3DOM Research Unit of FBK, and is embedded with MAIA multispectral camera.

SAL Engineering is a company specialized in photogrammetric surveys based in Italy: please visit our website www.salengineering.it.

For any further information about services and products, send us an email at info@salengineering.it.

For any detailed information about products and technologies that deal with multispectral surveys, please contact usSAL Engineering is providing accurate multispectral data to companies specialized in agronomic consulting thanks to our integrated systems based on platform, control system and sensors.

MAIA WV is the multispectral camera equipped with the same wavelenght intervals of the WorldView-2™ satellite owned by DigitalGlobe. Now, you can compare satellite data with high-resolution maps obtained through a multispectral survey conducted with MAIA WV mounted on your UAV, getting centimeters-level precision and accuracy. WorldView-2™ is a commercial earth observation satellite that provides eight-band multispectral imagery with 1.84 m resolution, in support of services such as agriculture, forest monitoring, land cover changes and natural disaster management. MAIA WV multispectral camera is based on an array of 9 sensors (1 RGB and 8 monochrome with relative band-pass filters) to detect multispectral imagery in the VIS-NIR spectrum from 390 nm to 950 nm: MAIA WV is the most advanced broadband multispectral camera for RPAS, aircrafts, terrestrial rovers available today, with bands in Coastal and Blue spectrum region.

Whereas MAIA S2 is the multispectral camera equipped with the same wavelenght intervals of the European Spatial Agency‘s Sentinel-2™ satellite. Sentinel-2™ is an earth observation mission developed by ESA as part of the Copernicus Programme to perform observations in support of services such as precision agriculture, forest monitoring, land cover changes detection, and natural disaster management. Now, you can compare free satellite data with high-resolution maps obtained through a multispectral survey conducted with MAIA S2, the multispectral camera with two narrow spectral bands both in Red Edge and in NIR region.

The key features of the new-born MAIA M2, that presents the same quality of sensors, filters and optics of the standard versions WV and S2, are basically linked to the modular system and to the freedom to customize the set of bandpass filters, with excellent cost/benefit ratio and perfect physical adaptability onboard data acquisition platforms.