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Comment by nologic01 | Hacker News Reader

If you (like me) wondered why go back decades to what is pressumably lower quality imagery than what is available today, here is the spoiler:

> They (cold war era) “preserve a high-resolution, stereo perspective on a landscape that has been severely impacted by modern-day land-use change”

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Not only that, but

> In addition, many of the likely Roman forts we have documented in this study have already been destroyed by recent urban or agricultural development, and countless others are under extreme threat.

How does this happen? Do you just see a bunch of ruins on your land and think "well if it was important people would know about it! Let's toss all this stuff in dumpster!"?

I can't imagine how many things went down like that. Large Dinosaur repositories and people trying to plant some vegetables were like "geez another bunch of bones. Alright, into the fire"

Yes. Altruism does not scale. It is very likely they thought, “oh, this is some old looking shit but doesn’t look that important. Better clean it up quickly before the preservationists come in and bankrupt this project.”

Certain groups of islamofascists intentionally destroyed known artifacts, ruins and even excavated and preseved sites like Palmyra during earlier stages of the Syrian Civil War.

Also in areas that are in war time conflicts, or in poverty, preserving may not be a top priority.

For example Gaza is the site of many historic cities dating thousands of years old.

Lots of people are highly motivated by the need to eat and don’t have the luxury of caring about history.

In most of Europe (and probably elsewhere), you can’t throw a rock without hitting some sort of historically significant thing.

We used to smoke weed on the local Roman wall. It was also a popular destination for rock climbers to practice. The wall has been there for 2000 years. It’s fine.

It's a bunch of stones. How would anyone know whether it was 200 years old or 2000? You can't ask archeologists in for every old cowshed built by your great grandfather!

Somewhat; Tim Traveler recently visited a 5,000-year-old dolmen in France, and it's preserved, but treated like any other small roadside attraction https://www.youtube.com/watch?v=1S6wP8ox1R4

I can't really watch the video but a dolmen in France is just a small roadside attraction, there are so many and they are usually on private property, you can't build a museum and visitors center around every single dolmen.

When living within any era, it is really hard to appreciate how much of the stuff we value (and what we don't) is just a cultural convention specific to that era (and with a high degree of arbitrariness).

People historically would routinely recycle anything of value and reusability. What has survived from previous times is more or less by accident (too bulky, too hidden etc.)

The idea of trying to preserve historical artifacts seems to be entirely modern, but even that concept has evolved alot. In the 19th century people did not think twice about mutilating and removing pieces to remote museums or "restoring" sites purely speculatively.

Your point is well-taken, but there is:

https://en.m.wikipedia.org/wiki/Ennigaldi-Nanna%27s_museum

It's one of my favorite archeological finds ever.

I suspect that there have been people in every age who valued, preserved, and studied material remains of the past. At a broad social and cultural level, however, you are correct.

Thanks for that - never heard of Ennigaldi-Nanna's museum before. Amazing to think that ~2,500 years ago, they had artifacts on exhibit that were already ~1,500 years old at that time. And labels in three different languages - all they were missing was the audio guide!

It is not that strange - they were no cavemen. This was in Pythagoras days.

First Pompeii excavation was in 1693. Even medieval Christianity is based on preserving historical artifacts.

On the other hand what you say about recycling and/or not preserving is true. And is happening even today.

These two things goes parallel through history.

This still happens today. For example, city walls of Moscow were started to be dismantled in 19th century and whatever left was destroyed by the communists after revolution. To widen the roads in the center of the city the communists demolished 18th and 19th century historical buildings (luckily some other buildings were just moved away using rails).

Also new construction sometimes happens in the center and you cannot build something new without destroying a part of history first.

Was looking at picture of Red Gates the other day, too bad they got destroyed right after renovation.

a great example is the Rosetta Stone, a 2000 year old tablet that contained 3 translations of a proclamation by the King (Ptolemy V). It was discovered in Egypt by Napoleon's army and for the first time in the modern day allowed ancient Egyptian writing to be deciphered and read.

my favorite part of the story is, when the Rosetta Stone was discovered, it had been considered rubble and was being used as one of the bricks in some more recent construction.

One of the big sources of new runestone discoveries in Sweden is "load bearing part of someone's basement" (and that similarly some amount of the Acropolis turns up as having been used as construction material.)

This is human tradition, especially urban tradition. To raise the elevation of the city, and reuse the prior construction as the foundation and basement of the next. The old town in Naples has a section that is contoured in a half-circle arc to align with a Roman amphitheater that now serves as its foundation. Reduce reuse recycle used to be taken much more seriously. :)

The Basilica Cistern in Istanbul is a great example too. The cistern itself is Roman, but they used bits of even older buildings to build it.

Construction involving digging is nearly impossible in most European cities because it's impossible to dig without hitting ruins. Rural areas aren't that much better. And it all has SOME historic value.

[https://www.reuters.com/article/us-italy-politics-metro/rome...]

For the most part, now it's 'take pictures, grab anything that looks particularly interesting, and bulldoze on'.

At some point, especially if you're a random not-super-wealthy farmer in the middle of nowhere, you have to go 'fuck it, whatever' or you're going to not get anything done.

> 'take pictures, grab anything that looks particularly interesting, and bulldoze on'

I've seen archeological survey like this. They explored construction site to ~1m depth. Found few things and went away. Then construction continued - in the depth of 2m vaults of (probably) gothic cellar appeared. Workers took few bricks home and continued with constructions of foundation and underground garage.

I remember going to a museum and seeing a 150 year old tool (a cant hook) that was in worse shape than the identical version my father had in his garage and was still using as a tool.

Time scales are much larger of course, but at some point these are just "old things" to the people involved.

You don't see any ruins. You see a slight bumps in terrain or grass patches that turn yellow a few days earlier each year. Only taking a picture from hundreds of feet above, with favorable lighting when shadows are long reveals regular rectangles, old plough marks and shapes of buildings that were leveled thousands years ago earlier. People like Podebard would come back to the same places for years just to catch that ideal conditions and discover additional detail or missed structures that were not visible on any previous picture.

There were Roman excavations in area of castle in my city. They were replaced by underground garages.

How did they get the stereo perspective, did they use a delay between photos from the same satellite so there was enough time for it to travel?

>The first CORONA satellites had a single camera, but a two-camera system was quickly implemented.[40] The front camera was tilted 15° aft, and the rear camera tilted 15° forward, so that a stereoscopic image could be obtained

https://en.wikipedia.org/wiki/CORONA_(satellite)#Cameras

And then you can view them with something like this: https://en.wikipedia.org/wiki/Stereoscope

There are different ways to do it, that's one of them.

A lot of the techniques were first used with airplanes, then later with satellites. Lots of overlap because planes allowed for easier localization and better resolution, especially earlier on in remote sensing.

I've done this from a plane before and got some very epic 3D images. I think Mt. Rainier at sunset was one of the best. So yeah, the easy way if your camera is on a moving platform, is take a shot, count three aligators, then take another shot.

I find stereo pair aerial imagery hugely helpful in understanding terrain. While Google Earth is great to get a gross overview, our eyes are much better at inferring sub-meter detail from pairs of stereo photos, e.g. from a single airplane taken a few seconds apart.

What are some good sources of public aerial stereo imagery? The only source I've found is NOAA https://www.noaa.gov/topic-tags/aerial-imagery

I wonder if it means photogrammetry can be used (eg. OpenDroneMap) to construct a 3D model of the landscape/buildings...

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