Big Data

Why we shouldn’t trust everything we see in satellite images

Geospatial data offers a powerful new way to see the world. But caution is key.

In 1972, the crew of Apollo 17 captured what has become one of the most iconic images of the Earth: the Blue Marble. Biochemist Gregory Petsko described the image as “perfectly representing the human condition of living on an island in the universe.” Many researchers now credit the image as marking the beginning of environmental activism in the US.

The Blue Marble. Photo credit: NASA/Wikimedia Commons [Licensed under Creative Commons]
The Blue Marble. Photo credit: NASA/Wikimedia Commons [Licensed under Creative Commons]

Satellite images are part of the big data revolution. These images are captured through remote sensing technologies – like drones, aerial photographs and satellite sensors – without physical contact or firsthand experience. Algorithms refine this data to describe places and phenomena on the Earth’s surface and in the atmosphere.

As a geographer, I work with geospatial data, including satellite images. This imagery offers a powerful way to understand our world.

But I think it’s important for people to understand the limitations of this technology, lest they misunderstand what they see.

What satellites show us

Satellite imagery has made a difference in a wide variety of fields and industries.

For example, in 1973, satellite images were first processed to demonstrate seasonal vegetation change. This information now helps to monitor vegetative health and track droughts around the world.

Images also provide evidence of compelling stories about the power of disasters. For example, in 1986, combined data modeled from satellite images and weather data tracked the plume of radiation from the explosion of the Chernobyl reactor in the USSR. More recently, before and after images of the impact of Hawaii’s Kilauea volcano revealed the flow of lava and loss of homes and businesses.

Satellite images track the changing human footprint across the globe, including rapidly growing cities, urban sprawl and informal settlements.

Kibera, the largest slum in Africa, in Nairobi, Kenya. Satellite images reveal the urban form of this Kenyan city, shown by the organisation of roads and buildings, adjacent land uses, and rooftops that may indicate types of building materials associated with economic conditions. Google Earth, annotations by Melinda Laituri, CC BY
Kibera, the largest slum in Africa, in Nairobi, Kenya. Satellite images reveal the urban form of this Kenyan city, shown by the organisation of roads and buildings, adjacent land uses, and rooftops that may indicate types of building materials associated with economic conditions. Google Earth, annotations by Melinda Laituri, CC BY

Increasingly, satellite imagery is used to measure, identify and track human activity. In 1995, satellite images provided evidence of mass executions in Srebrenica, in former Yugoslavia. In 2014, satellite images exposed the extent of the destruction of cultural heritage sites in northern Iraq and Syria. Last year, satellite images revealed the burning of Rohingya villages in Myanmar.

What’s missing from satellite images

But there are some caveats that anyone working with satellite images – or viewing them – should consider.

Satellite images are only as good as their resolution. The smaller the pixel size, the sharper the image. But even high-resolution images need to be validated on the ground to ensure the trustworthiness of the interpretation. Should we question the images we see? Whose view of the world are we seeing?

One example of the misuse of remotely sensed data was in 2003, when satellite images were used as evidence of sites of weapons of mass destruction in Iraq. These images revealed what were identified as active chemical munitions bunkers and areas where earth had been graded and moved to hide evidence of chemical production. This turned out not to be the case.

What’s more, processing satellite images is computationally intensive. At best, satellite images are interpretations of conditions on Earth – a “snapshot” derived from algorithms that calculate how the raw data are defined and visualized.

This has created a “black box,” making it difficult to know when or why the algorithm gets it wrong. For example, one recently developed algorithm is designed to identify artillery craters on satellite images – but the algorithm also identifies locations that look like craters but aren’t. How can experts sift through data that may yield imperfect results?

Through platforms like Google Earth and Earth Explorer, satellite images are increasingly available to not only researchers and scientists, but to people around the world. Satellite imagery is the basis for a global effort to map the world’s communities, such as OpenStreetMap, a platform where high-resolution imagery is used to digitize maps. Maps become living documents, always in a state of flux as new elements are added, often by remote mappers.

With this increasing practice, maps derived from satellite images are constructed by those who may not be very familiar with the site. Mappers have an important responsibility when representing other people’s places. Maps derived from satellite images without local context – like street names or information about vegetation types – tell incomplete stories. Building footprints can be digitized, but only locals can identify the purpose of that building. Imaginary lines, like country boundaries, don’t show up on remotely sensed images.

As satellite images become more ubiquitous, we should reflect on where they come from, how they are created, and the purpose for their use.

Melinda Laituri is a professor of Ecosystem Science and Sustainability at Colorado State University.

This article first appeared on The Conversation

Support our journalism by subscribing to Scroll+ here. We welcome your comments at letters@scroll.in.
Sponsored Content BY 

Swara Bhasker: Sharp objects has to be on the radar of every woman who is tired of being “nice”

The actress weighs in on what she loves about the show.

This article has been written by award-winning actor Swara Bhasker.

All women growing up in India, South Asia, or anywhere in the world frankly; will remember in some form or the other that gentle girlhood admonishing, “Nice girls don’t do that.” I kept recalling that gently reasoned reproach as I watched Sharp Objects (you can catch it on Hotstar Premium). Adapted from the author of Gone Girl, Gillian Flynn’s debut novel Sharp Objects has been directed by Jean-Marc Vallée, who has my heart since he gave us Big Little Lies. It stars the multiple-Oscar nominee Amy Adams, who delivers a searing performance as Camille Preaker; and Patricia Clarkson, who is magnetic as the dominating and dark Adora Crellin. As an actress myself, it felt great to watch a show driven by its female performers.

The series is woven around a troubled, alcohol-dependent, self-harming, female journalist Camille (single and in her thirties incidentally) who returns to the small town of her birth and childhood, Wind Gap, Missouri, to report on two similarly gruesome murders of teenage girls. While the series is a murder mystery, it equally delves into the psychology, not just of the principal characters, but also of the town, and thus a culture as a whole.

There is a lot that impresses in Sharp Objects — the manner in which the storytelling gently unwraps a plot that is dark, disturbing and shocking, the stellar and crafty control that Jean-Marc Vallée exercises on his narrative, the cinematography that is fluid and still manages to suggest that something sinister lurks within Wind Gap, the editing which keeps this narrative languid yet sharp and consistently evokes a haunting sensation.

Sharp Objects is also liberating (apart from its positive performance on Bechdel parameters) as content — for female actors and for audiences in giving us female centric and female driven shows that do not bear the burden of providing either role-models or even uplifting messages. 

Instead, it presents a world where women are dangerous and dysfunctional but very real — a world where women are neither pure victims, nor pure aggressors. A world where they occupy the grey areas, complex and contradictory as agents in a power play, in which they control some reigns too.

But to me personally, and perhaps to many young women viewers across the world, what makes Sharp Objects particularly impactful, perhaps almost poignant, is the manner in which it unravels the whole idea, the culture, the entire psychology of that childhood admonishment “Nice girls don’t do that.” Sharp Objects explores the sinister and dark possibilities of what the corollary of that thinking could be.

“Nice girls don’t do that.”

“Who does?”

“Bad girls.”

“So I’m a bad girl.”

“You shouldn’t be a bad girl.”

“Why not?”

“Bad girls get in trouble.”

“What trouble? What happens to bad girls?”

“Bad things.”

“What bad things?”

“Very bad things.”

“How bad?”

“Terrible!!!”

“Like what?”

“Like….”

A point the show makes early on is that both the victims of the introductory brutal murders were not your typically nice girly-girls. Camille, the traumatised protagonist carrying a burden from her past was herself not a nice girl. Amma, her deceptive half-sister manipulates the nice girl act to defy her controlling mother. But perhaps the most incisive critique on the whole ‘Be a nice girl’ culture, in fact the whole ‘nice’ culture — nice folks, nice manners, nice homes, nice towns — comes in the form of Adora’s character and the manner in which beneath the whole veneer of nice, a whole town is complicit in damning secrets and not-so-nice acts. At one point early on in the show, Adora tells her firstborn Camille, with whom she has a strained relationship (to put it mildly), “I just want things to be nice with us but maybe I don’t know how..” Interestingly it is this very notion of ‘nice’ that becomes the most oppressive and deceptive experience of young Camille, and later Amma’s growing years.

This ‘Culture of Nice’ is in fact the pervasive ‘Culture of Silence’ that women all over the world, particularly in India, are all too familiar with. 

It takes different forms, but always towards the same goal — to silence the not-so-nice details of what the experiences; sometimes intimate experiences of women might be. This Culture of Silence is propagated from the child’s earliest experience of being parented by society in general. Amongst the values that girls receive in our early years — apart from those of being obedient, dutiful, respectful, homely — we also receive the twin headed Chimera in the form of shame and guilt.

“Have some shame!”

“Oh for shame!”

“Shameless!”

“Shameful!”

“Ashamed.”

“Do not bring shame upon…”

Different phrases in different languages, but always with the same implication. Shameful things happen to girls who are not nice and that brings ‘shame’ on the family or everyone associated with the girl. And nice folks do not talk about these things. Nice folks go on as if nothing has happened.

It is this culture of silence that women across the world today, are calling out in many different ways. Whether it is the #MeToo movement or a show like Sharp Objects; or on a lighter and happier note, even a film like Veere Di Wedding punctures this culture of silence, quite simply by refusing to be silenced and saying the not-nice things, or depicting the so called ‘unspeakable’ things that could happen to girls. By talking about the unspeakable, you rob it of the power to shame you; you disallow the ‘Culture of Nice’ to erase your experience. You stand up for yourself and you build your own identity.

And this to me is the most liberating aspect of being an actor, and even just a girl at a time when shows like Sharp Objects and Big Little Lies (another great show on Hotstar Premium), and films like Veere Di Wedding and Anaarkali Of Aarah are being made.

The next time I hear someone say, “Nice girls don’t do that!”, I know what I’m going to say — I don’t give a shit about nice. I’m just a girl! And that’s okay!

Swara is a an award winning actor of the Hindi film industry. Her last few films, including Veere Di Wedding, Anaarkali of Aaraah and Nil Battey Sannata have earned her both critical and commercial success. Swara is an occasional writer of articles and opinion pieces. The occasions are frequent :).

Watch the trailer of Sharp Objects here:

Play

This article was published by the Scroll marketing team with Swara Bhasker on behalf of Hotstar Premium and not by the Scroll editorial team.