Trying to recreate an aerial photo from the 1930s

[JethroXP]

I live in a small town, and I’ve come across an aerial photo of the town from the 1930s. I think it would be cool to take a photo from (roughly) the same altitude, heading, and angle with my Mavic 2 to compare how the town has grown since then. I’ve tried visually matching, and I think I’ve gotten close, but I can tell something still isn’t right. Is there a technique, perhaps something used in aerial reconnaissance that I can use to mathematically get much closer than I am able to by visual comparison?

 

[zocalo]

If the original photo was done professionally then they may have used a tilt-shift (or perspective correction) lens to get more depth of field over the built up area. This would basically put the plane of critical focus more or less along the ground, but will result in some apparent differences in how buildings appear in relation to each other.

If you want all the gory details, Google "Scheimpflug principle".

 

[ac0j]

If the original photo was done professionally then they may have used a tilt-shift (or perspective correction) lens to get more depth of field over the built up area. This would basically put the plane of critical focus more or less along the ground, but will result in some apparent differences in how buildings appear in relation to each other.

If you want all the gory details, Google "Scheimpflug principle".

Was that a thing in the 1930's? I am impressed if it was!

I would just get in the air in the general area and just take a ton of shots, moving around after every shot. Up, Down, left, and right. The cross my fingers! I would love to see what you end up with! Cool idea!

 

[JethroXP]

Was that a thing in the 1930's? I am impressed if it was!

I would just get in the air in the general area and just take a ton of shots, moving around after every shot. Up, Down, left, and right. The cross my fingers! I would love to see what you end up with! Cool idea!

I’ve done that, which has gotten me to this point. I can align major features in one plane, such as the river, but features nearer and farther don’t align. This video shows what I’ve done so far. Note that the bridge shown actually is aligned. The old photo shows the original bridge, which was torn down and rebuilt in the 60s and repositioned one block farther north from the original.

https://youtu.be/fkmw7o_JCrs

 

[ac0j]

It might well be all about the lens characteristics. May be impossible to get perfect.

 

[JethroXP]

It might well be all about the lens characteristics. May be impossible to get perfect.

Not looking for perfect, just better. I think I need to spend some time on Google Earth measuring distance and angle between features in the old photo that still exist today and then apply some trigonometry to figure out the angle and distance of the camera from those features in the original. Was just hoping there might be some “off the shelf” solution or method for this.

 

[Kilrah]

Probably taken at about the same angle but higher and farther with a longer lens. With the M2P you'd have to go to that point and do a bunch of cropping/distorsion correction to try and mimic that.

But probably what causes most visible difference and lack of appeal is that on the old photo the roads are prominent and kind of the main subject, yet now you pretty much can't see them at all and there's nothing to attract your eye anymore.

 

[AMann]

You are also dealing with yourr own lens’ barrel distortion and some rubber sheeting will be needed to match it correctly. Do you have Photoshop? It would be simple to match there.

 

[JethroXP]

Probably taken at about the same angle but higher and farther with a longer lens. With the M2P you'd have to go to that point and do a bunch of cropping/distorsion correction to try and mimic that.

But probably what causes most visible difference and lack of appeal is that on the old photo the roads are prominent and kind of the main subject, yet now you pretty much can't see them at all and there's nothing to attract your eye anymore.

Yeah, I think I need to go higher as well. I don't have photoshop (can't bring myself to pay Adobe $20 per month or whatever it is for life) but I do have PaintShop Pro.

 

[zocalo]

Was that a thing in the 1930's? I am impressed if it was!

Yep, the technique itself was developed and formalised very early on (1904!), with some initial aerial usage taking place for battlefield surveys during WW1. Lens tilt is a really cool thing to play around with as well - I have a medium format view camera with full movements and a TS-E lens for my DSLR - but probably not going to be an option on all but the highest end drones any time soon, unfortunately.

 

[Kilrah]

There's also the little complication of actually adjusting the many degrees of freedom of the lens properly in flight

 

[sar104]

Your attempt already looks remarkably good to me. Doing better than that will be a challenge.

 

[JethroXP]

I know nothing about the origin of the photo, even the year it was taken is really just a guesstimate. I doubt it was a professional photo with lens tilt, as there simply wasn't much in the town at that time worth that kind of expense I suspect it was just some guy hanging out the door or window of a small plane with a camera.

 

[AMann]

I like the project though, it looks good. II was involved in a similar one for NPR and it was fun.

 

[JethroXP]

There's also the little complication of actually adjusting the many degrees of freedom of the lens properly in flight

Of the six degrees of freedom I can think of, I think I only need to account for four, maybe five of them in flight (X, Y, Z, pitch and maybe yaw) but roll I should be able to account for in post processing. So it’s not a horrible problem [emoji6]

 

[Kilrah]

I was actually talking about the "tilt/shift lens on a drone" thing in the post directly above mine.

 

[zocalo]

There's also the little complication of actually adjusting the many degrees of freedom of the lens properly in flight

Yeah, you'd either need mechanically controlled lens movements or have it preset for a given altitude and camera angle in relation to the centre of the area of ground being imaged. You're probably only going to be using tilt in a fixed plane for this, so either way it would mostly be a case of adjusting the camera/lens tilt angle so the lens bisects the angle between sensor and ground, which is how military/recon applications work.

Definitely not something DJI is likely to be bringing out as standard any time soon, I think - more the realm of Boeing, Lockheed, et al., although it might make an interesting project for someone with an SLR-capable drone and something like a Raspberry Pi, or as a dedicated albeit niche product for a high-end ground survey drone.

 

[Cymruflyer]

I know nothing about the origin of the photo, even the year it was taken is really just a guesstimate. I doubt it was a professional photo with lens tilt, as there simply wasn't much in the town at that time worth that kind of expense I suspect it was just some guy hanging out the door or window of a small plane with a camera.

Generally for aerial photos of home and towns, they did not use tilt shift. That sort of lens is generally used for photographing buildings from the ground, to eliminate the converging verticals effect when using a wider lens tilted upwards.

 

[theDRONEranger]

I live in a small town, and I’ve come across an aerial photo of the town from the 1930s. I think it would be cool to take a photo from (roughly) the same altitude, heading, and angle with my Mavic 2 to compare how the town has grown since then. I’ve tried visually matching, and I think I’ve gotten close, but I can tell something still isn’t right. Is there a technique, perhaps something used in aerial reconnaissance that I can use to mathematically get much closer than I am able to by visual comparison?

Not part of the forum chat, but got something for you (free) if you want. Contact me off line if interested.

 

[AMann]

A good photo editing program like PS or GIMP (free from GIMP.org) can “rubber sheet” adjust the two photos to fit together. I used to do it for work as a cartographic tech.