Aerial mapping project shows how much American cities have changed

In 1957, most of the land surrounding Tempe, Arizona, was farmland. Fast forward to 2013 and the city has expanded, all the once-open fields have been filled with neighborhoods. This dramatic change – among others – can be seen and compared on interactive mapping project, Historic Aerials. 

Run by Nationwide Environmental Title Research (NETR), Historic Aerials has amassed millions of aerial maps from as far back as the 1920s. The project, based in Tempe, is putting all the maps into an interactive viewer where visitors can see what a city or neighborhood looked like in the past and even compare to other decades, using the viewer's scroll and spotlight tools. They can also overlay roads, county lines and city lines over the aerial images.

Every day, the small team that works on Historic Aerials adds thousands of images to their platform after adjusting them so the images from different decades can be matched and laid over each other – a process that is difficult and time consuming and seemingly endless, NETR President Brett Perry says.

'Taking on this project is like eating an elephant,' he tells DailyMail.com. 'It's just so huge because the process of doing this is no easy task.'

1970, TEMPE ARIZONA: Within 13 years, the city had grown considerably. By this time the population was 63,550 and construction was beginning on housing developments outside the city limits 

1957 AND 1970, TEMPE ARIZONA: Historic Aerials is a mapping project based in Tempe, Arizona, that allows viewers to compare aerial maps from different years and decades. Tempe and the surrounding area are pictured above left in 1957, showing extensive farmland around where the city lies today but the city was already growing considerably. Between 1950 and 1960, the population increased by more than 17,000 to 24,897. Within 13 years, (1970, right) the city had grown considerably. By this time the population was 63,550 and construction was beginning on housing developments outside the city limits

1993, TEMPE ARIZONA: The Historic Aerials project has already amassed more than a million aerial maps from as far back as the 1920s in some areas, and when compared, the images show the drastic changes in some cities and neighborhoods

1993, TEMPE ARIZONA: The Historic Aerials project has already amassed more than a million aerial maps from as far back as the 1920s in some areas, and when compared, the images show the drastic changes in some cities and neighborhoods

2013, TEMPE, ARIZONA: By 2013, the aerial map of Tempe has changed beyond recognition. Gone is the farmland, replaced with more densely populated land. By 2016, the city's population stood at 182,498

2013, TEMPE, ARIZONA: By 2013, the aerial map of Tempe has changed beyond recognition. Gone is the farmland, replaced with more densely populated land. By 2016, the city's population stood at 182,498

NETROnline, as Perry puts it, is a 'niche title company' that does investigative title work, mostly for environmental purposes, such as finding property ownership history, determining property boundaries and finding who may have contributed to contamination. In the late '90s, Perry says, the company 'kind of ventured into the internet, just really by accident'. They had abstracters around the country who were doing research for them and county assessors and recorders were beginning to put information online, so Perry decided it would be a good idea to organize everything onto a website.

'By just weird luck, it was picked up by USA Today as being the best free public record site,' he says. 'I was like, oh my gosh, what did I do here by accident? ... We found something that was useful for our office that other people found and found useful as well.'

That got Perry thinking about what other digital products NETR could use and sell. Around the same time, the company had a client, a big oil company, in a dispute in Phoenix over which of two gas stations was responsible for contamination, one owned by NETR's client and the other owned by another company. As Perry was looking through some of the aerial images from different years, he struggled to compare because the aerial images weren't spatially correct and images from different years didn't match. It was then that it occurred to him how useful it would be if they did match.

'It always kind of stuck in my mind and then [I was] talking to a big, local aerial company here and he was telling me about some sources of aerial imagery and I started thinking about that and I just thought, maybe I will create a website where we would orthorectify this stuff and basically be able to create this virtual time machine.'

1954, LOWER MANHATTAN: The Lower West side of Manhattan as seen before an urban regeneration project, led by David Rockefeller, that saw the building of the Twin Towers. The clearing of an area known as Radio Row around Greenwich and Cortland streets spawned much protest but the development went ahead and the area - blocks of electronics stores - was cleared by 1966. To the left of the map, piers can be seen jutting out into the Hudson River. Soon they would be consumed under landfill from the rubble excavated when foundations were dug for the World Trade Center beginning in August 1966

1954, LOWER MANHATTAN: The Lower West side of Manhattan as seen before an urban regeneration project, led by David Rockefeller, that saw the building of the Twin Towers. The clearing of an area known as Radio Row around Greenwich and Cortland streets spawned much protest but the development went ahead and the area - blocks of electronics stores - was cleared by 1966. To the left of the map, piers can be seen jutting out into the Hudson River. Soon they would be consumed under landfill from the rubble excavated when foundations were dug for the World Trade Center beginning in August 1966

1980, LOWER MANHATTAN: Urban regeneration in action on the Lower Westside of Manhattan where the Twin Towers can be seen by 1980. Construction work began on the North Tower in 1968 and on the South Tower in 1969. Just over two years later in December 1970, the first tenants moved into the North Tower and the South Tower was first occupied in 1972. Also to the left is the bald footprint of Battery City Park, which expanded the island's width using materials excavated during the construction of the World Trade Center

1980, LOWER MANHATTAN: Urban regeneration in action on the Lower Westside of Manhattan where the Twin Towers can be seen by 1980. Construction work began on the North Tower in 1968 and on the South Tower in 1969. Just over two years later in December 1970, the first tenants moved into the North Tower and the South Tower was first occupied in 1972. Also to the left is the bald footprint of Battery City Park, which expanded the island's width using materials excavated during the construction of the World Trade Center

2004, LOWER MANHATTAN: Three years after the September 11 atrocity on the World Trade Center, the scale of the Ground Zero clean-up can be seen in this map. To the left, the development of Battery City Park is well underway

2004, LOWER MANHATTAN: Three years after the September 11 atrocity on the World Trade Center, the scale of the Ground Zero clean-up can be seen in this map. To the left, the development of Battery City Park is well underway

2013, LOWER MANHATTAN: By 2014, the north and south pools of the National September 11 Memorial can be seen clearly on the aerial map above

2013, LOWER MANHATTAN: By 2014, the north and south pools of the National September 11 Memorial can be seen clearly on the aerial map above

Since its start around 2005, Historic Aerials has collected more than a million aerial maps from various sources including a private aerial company they bought out, which had about three or four hundred thousand images – on the low side for the total collection, Perry says. Other image sources include the Army Corps of Engineers and the Farm Bureau.

Only seven people in the NETR offices work on Historic Aerials, where they take the aerial images, scan them, orthorectify, or correct, them – which entails finding the altitude of the plane that took the images, the type of lens used for the images, the ground elevation and control points on the ground – using a specific software that stretches the image to be spatially correct and mosaic a series of images to be seamless for the website viewer.

In the early days of Historic Aerials, the process was slow and tedious, but Perry says he's glad for the learning curve because of the technological advancements that have since come along.

'If we would have spent tons and tons of resources early on, I think the quality, what we show today, wouldn't be as good, 'cause nowadays we're scanning things five times better than what we did 10 years ago and it just would have been impossible storage-wise… The fact that we were sort of slow-growing this thing has actually worked out to our advantage.'

Today the team publishes at least a thousand images every day, Perry says, but even though that sounds like a lot, there's still so much to do, even to just cover the whole US. He says they could probably go faster if they focused only on urban areas, but they've decided to cover all the deserts and mountains just as thoroughly.

'It can get frustrating sometimes, the images don't come together as easily as we'd like,' Perry says. 'Sometimes they come together like butter, but a lot of times, there's various things that we have to spend a little extra time and effort to actually get it to come together. And it's a slow process, but each year by magnitude, we increase our output. When we first started doing this, it was minuscule compared to what we can do today.

'I think if you would have told me when we first started that we would be producing what we do on a weekly basis, I would have told you you're crazy, because the output is- let's say a company as large as Google would struggle to keep up with us at this point.'

1950, LAS VEGAS: When Las Vegas was founded in 1905, the city limits were north of this aerial image, which shows only desert. In 1950 the population of Las Vegas was 24,624, according to the Las Vegas Convention and Visitors Authority

1950, LAS VEGAS: When Las Vegas was founded in

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