Multispectral data for environmental studies

Multispectral data for environmental investigations

SAL Engineering, in collaboration with ARPA Campania, carried out some experimental multispectral investigations to research the possibilities of development of the multispectral survey technology applied to environmental monitoring.

The University of Modena and Reggio Emilia has also conducted studies, research and insights on the data obtained, also through the thesis of Dr. Lisa Mosconi. The purpose of this thesis is to investigate the potential and problems related to the use of multispectral images acquired by sensors mounted on board of remotely piloted aircraft (APR), also called more commonly drones, for applications of environmental sciences and environmental protection.

These sensors are sensitive to radiation emitted or reflected on different wavelength intervals of the electromagnetic spectrum, from the visible region (VIS) to that of the near infrared (NIR) and it is precisely this ability to observe beyond the visible, side by side of the ‘high geometric resolution that can be obtained, which makes them particularly interesting for environmental investigations. The acquired data allow to obtain information regarding the stress or vigor of the vegetation, aspects that can also be correlated to other information depending on the territory considered.

The term “environmental investigations” therefore refers to a series of applications that include precision agriculture and the monitoring of portions of the territory affected by problems of soil and groundwater pollution.

In a waste disposal plant, the multispectral survey provides geometric and radiometric information useful to identify and diagnose any malfunctions in the management of wastewater and sewage produced by the decomposition of waste, to characterize the various infrastructures of the plant, to diagnose any phenological consequences and pathological effects on vegetation affected by contamination processes. In addition, it is possible to evaluate the presence or absence of a pollution by leachate inside the pipes and the surrounding soil.

All this was possible thanks to the innovative MAIA multispectral camera developed by SAL Engineering together with Eoptis mounted on board a multirotor drone, which allowed the acquisition of multispectral images, with a degree of detail and accuracy never achieved before.

MAIA M2: the modular multispectral camera

 

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.

SAL Engineering is a company specialized in photogrammetric surveys based in Italy: 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.

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.

“Geometric calibration and radiometric correction of the MAIA Multispectral Camera” on ISPRS Archives

Geometric calibration and radiometric correction of the MAIA Multispectral Camera

As a result of the Conference “Frontiers in Spectral imaging and 3D Technologies for Geospatial Solutions” that took place in Jyväskylä, Finland, on 25-27 October 2017, a paper has been discussed, published and scientifically reviewed. The title of the article is “Geometric calibration and radiometric correction of the MAIA Multispectral Camera” and it is published on “The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-3/W3, 2017”.  This article has been peer-reviewed.

Multispectral imaging is a widely used remote sensing technique, whose applications range from agriculture to environmental monitoring, from food quality check to cultural heritage diagnostic. A variety of multispectral imaging sensors are available on the market, many of them designed to be mounted on different platform, especially small drones. This work focuses on the geometric and radiometric characterization of a brand-new, lightweight, low-cost multispectral camera called MAIA. The MAIA camera is equipped with nine sensors, allowing for the acquisition of images in the visible and near infrared parts of the electromagnetic spectrum.
You can read and download the paper by clicking on the link below.