Help with LiDAR

[ohmygato]

As I'm getting back into the hobby, I've discovered that LiDAR has really advanced in the past decade to help with finding sites. However it seems that I'm way behind in figuring out how to use it to find good sites. I have an example I'd like to share to get some opinions on...

A friend and I have been researching old mountain resorts. From historical documents we believe that there were places where a lot of tourists congregated as well as structures that used to service these tourists. So far we've come up short with any good finds. However I recently saw on LiDAR a few spots that I definitely haven't searched yet. I'm using National Map to look at a few different layers of a site. This is the Open Street Map of the area (street names removed "to protect the innocent" ):

This is the same area with "Imagery (NAIP Plus)" and modern buildings highlighted as points of reference:

And finally this is the area with "3DEP Elevation - Hillshade", modern buildings again highlighted but also some red circled areas of interest:

The areas I've circled seem to have significant elevation changes and outline straight and perpendicular features. And as you can see there are no structures in these areas in the map or imagery. It does appear that there are some faint lines you can see in the imagery that might coincide with these features.

Could these be the locations of old structure foundations? Or is this too much of a stretch as far as analyzing LiDAR goes? Any advice is appreciated.

-Dan

 

[Dangerranger60]

I would be investigating those as old foundations. But I know nothing about LiDAR. Where do you find these LiDAR surveys? or are you doing them yourself? Enquiring minds need to know. DR

The good part is with the position of the current driveway or road the area should be easy to find. DR

 

[ohmygato]

I would be investigating those as old foundations. But I know nothing about LiDAR. Where do you find these LiDAR surveys? or are you doing them yourself? Enquiring minds need to know. DR

The good part is with the position of the current driveway or road the area should be easy to find. DR

I'm using the USGS National Map: https://www.usgs.gov/programs/national-geospatial-program/national-map. And this is the "3DEP" layer applied to it, whatever that is. I believe there are quite a few other resources available though. I'm a total beginner to this so it could be that there are way better options.

 

[JCR]

I have successfully used the same Lidar Hillshade overlays. What you have circled in red are definitely man made remnants. Almost certainly buildings. Also note the old roadbeds no longer utilized.

 

[Tom_in_CA]

Dan, just now seeing this post. Yes don't you remember that I told you that structures had been @ the south end of this field.

And yes that's very interesting that liDAR confirms this very thing, so that, even if you hadn't had records (via old topo maps and history books), that liDAR alone would have given you the same clue. Very very interesting.

 

[ohmygato]

I have successfully used the same Lidar Hillshade overlays. What you have circled in red are definitely man made remnants. Almost certainly buildings. Also note the old roadbeds no longer utilized.

Thank you very much! Do you happen to have any good references on how to do this LiDAR stuff? And can you say why "Almost certainly buildings"? Like it does look pretty obvious to me, but can you characterize what about those spots look like they were former buildings?

 

[JCR]

I don't have any references other than common sense & careful observation. I usually study the Lidar image after studying other sources like maps, aerial photos & written accounts. Any geometric shape on the ground is man made. There are very few straight lines in Nature.

 

[Kansashunter]

There is potential, check it out!!

 

[Dangerranger60]

I'm using the USGS National Map: https://www.usgs.gov/programs/national-geospatial-program/national-map. And this is the "3DEP" layer applied to it, whatever that is. I believe there are quite a few other resources available though. I'm a total beginner to this so it could be that there are way better options.

A very cool tool! I have a couple places near me that I have found by accident that I'm going to have to look at to see what else is there that I missed. Thanks DR

 

[Rock Jock]

Here's my take on the technology FWIW. I may have confused some stuff. LIDAR stands for "laser (or light) imaging & ranging". Laser scanning by drone, aircraft or satellite is used to catch reflections from the foliage canopy AND the ground or water surface (or structures). The reflection from the canopy is received earlier than the signal from the surface or structures (unless the structures are higher). The scan is processed to remove all the canopy signals mathematically. The residual signals from the ground and structures are mapped and the result is presented as a LIDAR layer. The layer presents the surface without the foliage canopy. Some resolution is better than others. More settled areas generally have superior resolution.
I subscribe to a mapping app called Caltopo which includes a layer called "slope shading", which is another name for a processed LIDAR layer. It helps to observe subtleties of ancient infrastructure such as abandoned old roads and cellar holes.

 

[ohmygato]

Here's my take on the technology FWIW. I may have confused some stuff. LIDAR stands for "laser (or light) imaging & ranging". Laser scanning by drone, aircraft or satellite is used to catch reflections from the foliage canopy AND the ground or water surface (or structures). The reflection from the canopy is received earlier than the signal from the surface or structures (unless the structures are higher). The scan is processed to remove all the canopy signals mathematically. The residual signals from the ground and structures are mapped and the result is presented as a LIDAR layer. The layer presents the surface without the foliage canopy. Some resolution is better than others. More settled areas generally have superior resolution.
I subscribe to a mapping app called Caltopo which includes a layer called "slope shading", which is another name for a processed LIDAR layer. It helps to observe subtleties of ancient infrastructure such as abandoned old roads and cellar holes.

As I understand it you are correct, but from what I've learned the ground layer is called a Digital Elevation Model (DEM). So there is the raw LiDAR data and then there is the DEM, then this can be further manipulated as "hillshade", "slope", etc.. The way you calculate the DEM from LiDAR is unclear to me. From what I've read it's "simple" algorithmic stuff, but all where you just throw the LiDAR file into an algorithm and it spits out the DEM.

 

[Rock Jock]

As I understand it you are correct, but from what I've learned the ground layer is called a Digital Elevation Model (DEM). So there is the raw LiDAR data and then there is the DEM, then this can be further manipulated as "hillshade", "slope", etc.. The way you calculate the DEM from LiDAR is unclear to me. From what I've read it's "simple" algorithmic stuff, but all where you just throw the LiDAR file into an algorithm and it spits out the DEM.

In a way it is not unlike the mathematical signal processing that seismic shoots undergo in the petroleum industry. They can do 2D lines as well as 3D matrix shoots to model the subsurface geology. Geophysics is an important tool for exploration for hydrocarbons and other resources and uses. Materials have differing sonic velocities and this is used as a method to test for counterfeit gold plated bullion coins and bars.

 

[BobOso]

Not trying to take over your thread, but how would you strip it down further! I've used that site a few times without success.
Here is the issue, in the photo, where the arrow points, there was several cabins as well as an A frame hoist over the mine shafts. Books show the pictures and the geological survey shows they were there even in the late 1970's. I've made many trips here, and have only found the pads for the A frame. The forest service kindly removed all trace of past life.Yet we are not allowed to remove anything older than 50 years, go figure.
Anyways there are many other sites such as this in the area, the forest service removed traces of about 15 small towns that had families that made a living from mining. I should add that I have found the old dumps containing bottles,cans, bed frames, but not much else. I have also flown my drone about the area, also no luck, so once again how would tou strip it further?

 

[ohmygato]

Not trying to take over your thread, but how would you strip it down further! I've used that site a few times without success.
Here is the issue, in the photo, where the arrow points, there was several cabins as well as an A frame hoist over the mine shafts. Books show the pictures and the geological survey shows they were there even in the late 1970's. I've made many trips here, and have only found the pads for the A frame. The forest service kindly removed all trace of past life.Yet we are not allowed to remove anything older than 50 years, go figure.
Anyways there are many other sites such as this in the area, the forest service removed traces of about 15 small towns that had families that made a living from mining. I should add that I have found the old dumps containing bottles,cans, bed frames, but not much else. I have also flown my drone about the area, also no luck, so once again how would tou strip it further?

Hi Bob,

You're not taking over the thread - I think a case study like this is exactly what is helpful to the discussion. If you're willing to share your site (coordinates, history, etc.) I would love to check it out and see if I can give you some ideas. You could add it to this thread or send me a PM if you prefer. But if you're reluctant to do that due to engendering competition or historical sensitivity that is no problem and I completely understand. However I don't know how much of a help someone could be with LiDAR or other tools without a very rough idea of where it's at. I will say I am based on the central coast of California and am respectful of people wanting to keep private sites to themselves.

From what limited things I've learned about mining towns, it's important to try to find out the areas of activity and habitation that are around the mine, not just the mine itself. So it's a great sign that you've found old dumps around here. Have you confirmed the age of your bottles and cans? Does the exact location of the dump show anything on imagery and/or history books that you could use to look for similar hot spots? It's important to keep in mind that some spots just don't even have any structures to associate with them, or at least nothing that can be seen on LiDAR. ...This would be my general thought process around what you're working on.

-Dan

 

[airbornebob]

I am currently trying to learn the nuances of Lidar. I am researching an old Boy scout camp outside of the town I live in. Here is what I have done so far...
1. Found the location on a 2013 National Geographic map

2. Checked the current Google map Image:

3. Went to Areial History and found an image from 1997

4. Then got this LiDar image (played around with the gray tones and shade settings)

This area is totally unused at present, with an Industrial Park now occupying the adjacent property. I am really excited about searching there when the weather gets more hospitable, the property is now owned by the county's industrial development board.

 

[JCR]

Once you have been on the ground at the site a few times, all your prior research will come together. You will observe/understand features that would have gone unnoticed without the prior research & study.

 

[BobOso]

Dan the location; 31°28'50.88"N 111°17'15.00"W

And I have been in this area and other spots nearby for the past 10 years, I've found traces of the past, such as old spoons, parts of pocket watches, old graves some dump sites, the age of the cans are old solder dots.
I've found mule shoes, early lead 2 ring and 3 ringers, and of course the usual stuff prospectors keep, like gold nuggets along with silver and copper nuggets. But only modern coins lost by hunters and campers.

 

[airbornebob]

there appears to be some structures North of the pits (red arrows). I used this site : https://apps.nationalmap.gov/viewer/

 

[ohmygato]

This area is totally unused at present, with an Industrial Park now occupying the adjacent property. I am really excited about searching there when the weather gets more hospitable, the property is now owned by the county's industrial development board.

Hi Bob,

I sussed out where you're looking and then looked up your site on The National Map. I think you have a VERY interesting site there. Lots of cool obvious man made features to check out in the woods. If I were you I would also look at what history you might be able to superimpose with that imagery you've pulled up. Like where were the biggest congregations of people there and highest levels of activity that could help to separate them from metal objects? This may come from scout history, local history, photos, etc. And also think about what kinds of things you might find there, meaning what ranges of targets will you be searching for if/when you're knee deep in trash or iron?

-Dan

 

[ohmygato]

there appears to be some structures North of the pits (red arrows). I used this site : https://apps.nationalmap.gov/viewer/

Yes exactly! And as you start to zoom out you can see all these little pits all over the place! What are these? Mines? Dumps?