24 June 2016

Sky survey, AMA recommendations say it's time to reduce light pollution

A major focus of the International Year of Light and Light-Based Technologies was raising awareness of light pollution. With the rapid dissemination of LED lighting, one unfortunate side-effect is the proliferation of a higher color-temperature illumination. This has many documented negative effects on wildlife behavior and migration, as well as on human circadian rhythms. In addition, scientists are studying further problems in human health that may be indirectly related to different lighting, including higher incidence of some cancers.

Meanwhile, cities and towns across the globe enthusiastically switch to LED street lighting. The energy savings are significant, but in news reports of the plans and projects, there is usually no mention of the technical specifics (or “warmth”) of the light. Early bright white LED streetlights were mostly above 4000K, whereas warmer versions are now available, 3000K or below.

One problem with extremely bright light is that it impairs vision in darker areas, so any illusion of safety at night vanishes as visibility diminishes once you get into a shadow. For drivers as well as pedestrians, this can be dangerous.

Now the American Medical Association (AMA) has issued guidance encouraging communities to adopt LED lighting that minimizes blue-rich light. The AMA also recommended that “all LED lighting should be properly shielded to minimize glare and detrimental human health and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods,” according to a press release.

“The guidance adopted by grassroots physicians who comprise the AMA's policy-making body strengthens the AMA's policy stand against light pollution and encourages public awareness of the adverse health and environmental effects of pervasive nighttime lighting,” the release says.

We requested a copy of the original report that led to these recommendations from the AMA. Here’s an excerpt:

More recently engineered LED lighting is now available at 3000K or lower. At 3000K, the human eye still perceives the light as “white,” but it is slightly warmer in tone, and has about 21% of its emission in the blue-appearing part of the spectrum. This emission is still very blue for the nighttime environment, but is a significant improvement over the 4000K lighting because it reduces discomfort and disability glare. Because of different coatings, the energy efficiency of 3000K lighting is only 3% less than 4000K, but the light is more pleasing to humans and has less of an impact on wildlife.

“Disability glare” is defined by the Lighting Research Center at Rensselaer Polytechnic Institute as “the reduction in visibility caused by intense light sources in the field of view [because of] stray light being scattered within the eye.”

One city that put the brakes on the brighter LEDs is Davis, California. In 2014, as new lights were being installed, the Davis city council put the project on hold after multiple complaints from residents. Later, the city decided to spend an additional $325,000 to replace those too-bright streetlights in residential areas. However, Davis is the exception. Places that have not yet committed to the switch are encouraged by the International Dark-Sky Association (IDA), the Lighting Research Center, and others to ask the right questions and study the issues involved beyond the simple let’s-save-energy approach. (In fact, that justification is up for debate as well -– it seems that when something gets cheaper, people tend to use more of it.)

Last fall, SPIE Newsroom published an article exploring these issues and collecting the advice of lighting experts. Recommendations for municipalities considering a change are included. (See “LED light pollution: Can we save energy and save the night?” by Mark Crawford.)

Just this month, a world atlas of artificial sky luminance, described in Science Advances reported that 80% of North Americans and one third of all humans are unable to see the Milky Way because of light pollution. Calculated with data from professional researchers and citizen scientists, the atlas also takes advantage of the newly available, low-light imaging data from the VIIRS DNB sensor on the Suomi National Polar-orbiting Partnership (NPP) satellite. The authors conclude:

"Light pollution needs to be addressed immediately because, even though it can be instantly mitigated (by turning off lights), its consequences cannot (for example, loss of biodiversity and culture)."

The IDA says this is a "watershed moment." The sky atlas and the AMA recommendations offer "an unprecedented opportunity to implore cities to transition to LEDs in the most environmentally responsible way possible." It's a good chance to start a conversation with your elected officials.

07 June 2016

Photonics on the farm: robotics to help feed the world

Simon Blackmore talks about farming with robots
for precision agriculture in an
SPIE Newsroom video interview [6:58].
Ten to 15 years ago, farmers used to laugh when Simon Blackmore and his colleagues talked about deploying robotics for such chores as weeding, protecting crops from disease or pests, or selecting harvest-ready vegetables — all while helping to cut costs and limit chemical and other impacts on the soil.

Now, he said in an SPIE Newsroom video interview posted last week, they’re asking questions about how robotics and other photonics-enabled technologies can help save energy and money, minimize soil damage, and improve crop yield.

Blackmore, who is Head of Engineering at Harper Adams University in Shropshire, director of the UK National Centre for Precision Farming (NCPF), and project manager of FutureFarm, also shared his ideas in a new conference at SPIE Defense and Commercial Sensing in April on technologies with applications in precision agriculture.

Blackmore and his NCPF colleagues are working to overhaul current farming practices by intelligently targeting inputs and energy usage. Their lightweight robots are capable of planting seeds in fields even at full moisture capacity, replacing heavy tractors that compact and damage the soil.

Simon Blackmore
Robots have also been designed with micro-tillage capabilities, to target the soil at individual seed positions, and for selective harvesting of crops for quality assurance.

“Now one of my former PhD students has developed a laser weeding system that probably uses the minimum amount of energy to kill weeds, by using machine vision to recognize the species, biomass, leaf area, and position of the meristem, or growing point,” Blackmore said.

A miniature spray boom of only a few centimeters wide can then apply a microdot of herbicide directly onto the leaf of the weed, thus saving 99.9% by volume of spray. Or, a steerable 5W laser can heat the meristem until the cells rupture and the weed becomes dormant. These devices could be carried on a small robot no bigger than an office desk and work 24/7 without damaging the soil or crop.

Not surprisingly, data is a hot topic in the field of precision agriculture.

Several speakers at the April event — among them John Valasek, and Alex Thomasson of Texas A&M University (TAMU), chairs of the conference, and Elizabeth Bondi of the Rochester Institute of Technology (RIT) — spoke about best practices for collecting data, and Kern Ding of California State Polytechnic University discussed data processing techniques.

Valasek also described several sensors and different ways they may be flown. Factors such as weather, speed, altitude, and frame rate can dramatically change the quality of the data products from UAV imagery.

Bondi discussed the calibration of imagery from UAVs (unmanned aerial vehicles, such as drones) to maintain consistency over time and under different illumination conditions.

Other speakers — Haly Neely of TAMU, Carlos Zuniga of Washington State University, and Raymond Hunt of the U.S. Agricultural Research Service — focused on the use of UAVs for such applications as soil variability, irrigation efficiency, insect infestation, and nitrogen management for crops including cotton, grapes, and potatoes.

Plant phenotyping — the analysis of crop characteristics such as growth, height, disease resistance, nutrient levels, and yield — is vital to increase crop production. Taking these data with current methods can damage plants, and is time-consuming and expensive. UAVs, carrying the right sensors, have the potential to make phenotyping more efficient and less damaging.

Speakers Yu Jiang of the University of Georgia, Andrew French of the U.S. Arid-Land Agriculture Research Center, and Grant Anderson of RIT described ground-based systems to expedite phenotyping, and Joe Mari Maja of Clemson University, Yeyin Shi of TAMU, Maria Balota of Virginia Polytechnic Institute, and Lav Khot of Washington State University discussed UAV-based systems.

With images and measurements from such devices, for example, cotton height may be determined and cotton bolls counted, soil temperature can be mapped, and nutrient levels in wine grapes were assessed remotely.

Small- and mid-sized farms are expected to see the largest yield increase from these initiatives. The ultimate result of all this photonics-enabled precision agriculture is profound: healthier food, more productive farms and gardens, and more nutritious food for a growing world population.

Thanks to Elizabeth Bondi and Emily Berkson, both of RIT, for contributions to this post.