Anyone casting their gaze skyward on a clear evening now typically sees more than just stars. Indeed, the night sky has become increasingly crowded, with at least 14,000 satellites currently in Earth’s orbit.
These satellites are integral to global communications, weather forecasting and GPS. They’re also revolutionising the remote sensing tools available to surveyors, as ever-higher resolution cameras enable imagery to leap from two to three dimensions – and there’s more to come.
When Google Earth’s 15-metre resolution satellite imagery debuted in 2005 with the capacity to illustrate 3D terrain and building models, it was deemed a revelation. The new technology was immediately put to use helping emergency responders during Hurricane Katrina. It went on to enable scientific discoveries like previously unknown coral reefs in Australia and archaeological fossil finds from Egypt to South Africa and the UK to the US.
But 15-metre resolution was not fine-grained enough for urban settings, like identifying individual structures for code compliance or monitoring building stock for asset management. That’s starting to change, however, with ever-higher resolution imagery that makes Google Earth look quaint.
Since July 2024, companies like Vantor (formerly Maxar) have offered imagery as precise as 15cm resolution in high-definition. That’s detailed enough to make out road markings, manhole covers, utility lines and other small objects in urban environments. Then there are other private-sector offerings from the likes of Steve Wozniak’s Privateer and Umbra. Satellogic will even sell customers their own personalised Earth observation satellite.
Some of these services tailor their offerings to the needs of the defence sector, security experts or the energy industry. For example, Black Sky can monitor border crossings for smuggling or critical infrastructure for saboteurs. But surveyors have found plenty of initial applications for high-resolution satellite imagery, from California insurers adjusting rates based on overhead observations to Stanford researchers studying the rate of legal compliance among builders of accessory dwelling units like granny flats.
SkyFi, a geospatial intelligence firm who began using Vantor maps in January, specifically bills itself as providing solutions for city planners with satellite-based building detection algorithms. And for those whose work focuses on the built environment, these ‘spacetech’ enterprises are soon to be joined by a Japanese consortium that pledges to update 3D maps of major cities every three to six months.
Starting next year, Marble Visions will launch its first satellite into space, bringing with it camera equipment that enables 40cm resolution imagery. Marble Visions, a subsidiary of Tokyo-based NTT Data, partnered with camera-maker Canon and geospatial surveyor PASCO on this endeavour, backed by the Japan Aerospace Exploration Agency’s Space Strategy Fund.
The human touch
What does this increasingly crowded marketplace mean for surveyors who suddenly have the ability to view any building up-close-and-personal in the world’s most populated precincts at the click of a mouse?
In a word, according to Marble Visions’ Julie Matsuoka, “efficiency”.
“Surveying will become more efficient by combining automated drones at micro-scales with satellite systems operating from space for much wider areas,” she says.
But as gizmos increasingly enter the equation, 3D satellite mapping backers insist there is still a role for the trained surveyor’s eye. “At very detailed scales, such as individual building sites or inside buildings, on-the-ground surveys by people will still be required,” says Matsuoka.
That concession backs up the sense of industry experts like Robert Herman MRICS. “3D satellite imagery is a meaningful upgrade from pure top-down views, but it does not eliminate the need for ground-level surveying,” he says. “It reduces blind spots, but does not resolve them.”
For Herman, co-founder and CEO of REscan, a California-based 3D mapping technology company focused on pedestrian and indoor spaces, distance is an inherent limitation of technology. “The satellites are [a long way] up there and even drones create distance,” he says. “Surveyors want to get something which is closer to the human.”
While a 3D satellite map could easily suffice for observing conditions in a large, unobstructed area like a quarry, Herman says the trained surveyor will still have to complement remote sensing to account for the complexity of the built environment. Basic components of construction like scaffolding are difficult for satellite imagery to penetrate and understand the exact condition of a building.
“Let’s face it, even at 15cm you won’t be able to make out cracks,” he says.
“Surveying will become more efficient by combining automated drones at micro-scales with satellite systems operating from space for much wider areas” Julie Matsuoka, Marble Visions
Digital twins: promise or peril?
At their most aspirational, Marble Visions and Vantor’s Vivid Mosaic offer a combination of high-resolution and frequent updates that allow for digital twins of urban environments.
“Traditionally, urban planning struggled with regularly updating digital maps,” says Matsuoka. “With comprehensive digital maps, the difficulty of regularly updating urban data will be resolved, enabling cities to be maintained as always up‑to‑date digital twins that can be actively used across a wide range of industries.”
But there are sceptics of these lofty visions. Pontus Westerberg is the executive director of Teaching Public Service in the Digital Age, an NGO that prepares public servants for the digital era. He casts a cautious eye toward the promises of digital twins for urban governance.
“A lot of these ideas come from a really tech-centric perspective without thinking about the actual use,” he says. “Yes, you can have a nice 3D model, but why would you want one apart from just looking at it?”
In his previous role leading digital technology initiatives at UN-Habitat, Westerberg encountered countless proposals for the applicability of digital twins, from modeling flood scenarios, to managing traffic flows, to identifying municipal water leaks.
While these goals are worthy challenges for local authorities to tackle, Westerberg reckons that a true digital twin for a major city would require more than just high-resolution, frequently updated 3D satellite maps. An accurate model would also necessitate an arsenal of sensors and video feeds for ground-level observation and a massive cloud capacity to store and manage the terabytes of data that such a project would generate. All of which costs a considerable amount of money in both hardware and software, as well as requires negotiating the delicate politics of privacy in local governments with a strong democratic culture.
More to the point, he says, local authorities make that kind of investment to what end? If the goal is to reduce traffic, for example, then urban design interventions that calm streets to reduce the volume of cars would be more effective. And while a 3D model of water infrastructure could identify leaks, there is a much more daunting task for cash-strapped local governments in actually fixing ageing infrastructure
“I’m not saying cities shouldn’t experiment, but one needs to be careful in making really big claims about what this is actually going to achieve,” he says.
