The new boydsmaps app is ready!

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
Is there a reason to keep this location secret instead of posting a link? Sorry, I know that this is Oyster Creek but don't have time to play "where is this" at the moment. :D

https://mobile.boydsmaps.com/#16.00/39.798224/-74.250081/lidar2021bw/0.00/0.00

Shadows are cast on the opposite side of an object from the light source. Since the source was at 45% (NE) that suggests the slope of the hill was facing SW (more or less) and therefore got a deep shadow. The higher the feature, the longer/darker the shadow. I know you dislike the moble app, but have a look there. Check my LIDAR HD 2021 map which uses different rendering parameters as well as color, it might reveal something.

https://mobile.boydsmaps.com/#16.00/39.798224/-74.250081/lidar2021hd/0.00/0.00

Then there are six different flavors of USGS LIDAR (that cover the entire US). The Aspect Map might be of interest, the metadata says "aspect map imagery is a color visualization of the compass direction that a hillside or slope faces".

https://mobile.boydsmaps.com/#16.00/39.798224/-74.250081/us3depAspect/0.00/0.00
 

bobpbx

Piney
Staff member
Oct 25, 2002
12,245
2,496
Pines; Bamber area
Is there a reason to keep this location secret instead of posting a link? Sorry, I know that this is Oyster Creek but don't have time to play "where is this" at the moment. :D

Hey, I tire of your odd, abrasive attitude sometimes, but I live with it. :D
 
  • Haha
Reactions: Boyd

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
OK, sorry, - fair enough. But let me just respectfully request that if you have a question about one of my maps, please post a link so that I can properly answer. If there's a reason not to reveal the location, you could send a private message.

As I said, the deepest shadows appear on the side of an object that is 180 degrees from the point source of light. If we moved the light source from 45 degrees to 90 degrees, it would reveal a whole different set of dark shadows.

It doesn't cover Ocean County, but you can observe the phenomenon on my LIDAR site. Run the West --> East slider back and forth and you can make "Devious" all but disappear!
 

bobpbx

Piney
Staff member
Oct 25, 2002
12,245
2,496
Pines; Bamber area
OK, sorry, - fair enough. But let me just respectfully request that if you have a question about one of my maps, please post a link so that I can properly answer. If there's a reason not to reveal the location, you could send a private message.

As I said, the deepest shadows appear on the side of an object that is 180 degrees from the point source of light. If we moved the light source from 45 degrees to 90 degrees, it would reveal a whole different set of dark shadows.

It doesn't cover Ocean County, but you can observe the phenomenon on my LIDAR site. Run the West --> East slider back and forth and you can make "Devious" all but disappear!
I was confused. I was thinking radar, not lidar (laser). Since Laser is light, it makes sense now. Nothing secret about the location. I just figured the question is general enough to understand. I only cared about the effect, not the place.
 

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
You've got the right idea, but actually, it doesn't matter what technology was used to capture the imagery. What you're viewing is a computer rendering of a three-dimensional surface. The location of the light source is what reveals the image. Obviously, if it were pitch black then you wouldn't see anything. The location of the light source is a choice by the map-maker, there aren't any standards that I'm aware of.

Bare-earth LIDAR only provides elevation data, hence the name "Digital Elevation Model" (DEM). Imagine a huge spreadsheet where the number in each cell is the elevation of one square meter on the map. It is (literally) that simple. An algorithm creates a triangular mesh interconnecting adjacent points in the grid. Then the brightness of each facet is calculated based on it's position relative to the light source.

So the way this data is represented on your screen really has nothing to do with how the elevation data was captured. I've heard that the earliest DEM data was manually created by putting 24k USGS topo maps on a graphics tablet, clicking points on the contour lines with a "puck" and manually entering the elevation. This kind of data could be rendered just the same as LIDAR today.

There's also radar data from the space shuttle that can also be processed exactly the same. It's all just a bunch of numbers representing the elevation of points in a grid. :)
 

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
Should also add that with LIDAR (as I understand it), you get multiple returns with each pulse that represent everything the beam passed through on its way to the bare earth surface. That is how the full point cloud dataset can represent a complete 3d model of everything (trees, buildings, etc). One ray could pass through a tree with leaves and branches, continue right through your house and finally bounce off the cellar floor. The bare-earth LIDAR I'm using strips away everything but the ground itself, so there's only one value for each point.

I have not studied the details of how they capture the data, just learning how to use it is hard enough. ;) But I assumed they use some kind of radar/laser technology since it obviously passes right through solid objects.
 

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
Another update to the app today. Bunch of changes "under the hood" to fix problems with switching between the GPS chip and USGS server for elevation. Let me know if you have problems, a quick test seemed good. There are now a total of 10 different maps of Vermont. Wanted to add two others but the server went down, which seemed like a good reason to take a dinner break. :D Will finish these tomorrow.


hillshade.jpg
 

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
More updates today. Added four more Vermont maps, which brings the map total for the site up to 125. :dance:

Here's a new feature that will make the site easier to use on a computer. You can now enable display of the full map URL in the web browser's address bar so that it continuously updates with any change of the map view (the same as online.boydsmaps.com).

examples.png

This makes it easy to copy links and save bookmarks if you use the site in a browser on your computer. But it should not be enabled if you're using the app on your phone. Enabling will affect performance, since the changing URL is constantly updated when the map moves. And the URL isn't shown in the app anyway, so there's no point in enabling it. :)

Generally speaking, unless you need this feature on your computer it's best to leave it disabled. Moving the map will be be less smooth when it's enabled. The mobile site has to work harder than the old online site since it renders the map in 3d and is also constantly updating the elevation when the map moves.

The URL will not be shown when GPS tracking is enabled, regardless of the preference setting.


urlPref.jpg
 
Last edited:

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
Today's update adds maps of New Hampshire. They have quite a few available, but are in the process of moving to a new site and there is very little documentation or metadata available. There are at least 8 more NH maps that I'll add soon.

mt-washington.jpg

Also updated the code for the URL display preference that was introduced yesterday. Now it doesn't update the URL until you stop moving the map, which results in smoother motion if URL display is enabled.

(If these new maps don't work for you, the usual disclaimers about clearing cache/site data apply. See earlier posts in this thread for instructions)
 
  • Like
Reactions: pinelandpaddler

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
Added some more New Hampshire LIDAR, still have more maps to add. But have a look at the NW and NE LIDAR, it's a good example of how lighting changes the appearance of the terrain (as discussed above)

https://mobile.boydsmaps.com/#11.00/43.770958/-71.267125/nhNWlidar/0.00/0.00


ossipee.jpg

Flip between the NW and NE versions and look how different they are. As I mentioned earlier, NH is moving all their geodata to a new site and there is very little metadata or documentation . So, it took me awhile to comprehend that these two maps both cover the entire state and the "NW" and "NE" titles refer to the direction of the light source. :)

BTW, according to the USGS topo, that unusual feature is called the Ossipee Mountains.
 
Apr 6, 2004
3,257
293
Galloway
Added some more New Hampshire LIDAR, still have more maps to add. But have a look at the NW and NE LIDAR, it's a good example of how lighting changes the appearance of the terrain (as discussed above)

https://mobile.boydsmaps.com/#11.00/43.770958/-71.267125/nhNWlidar/0.00/0.00


View attachment 15135

Flip between the NW and NE versions and look how different they are. As I mentioned earlier, NH is moving all their geodata to a new site and there is very little metadata or documentation . So, it took me awhile to comprehend that these two maps both cover the entire state and the "NW" and "NE" titles refer to the direction of the light source. :)

BTW, according to the USGS topo, that unusual feature is called the Ossipee Mountains.

Very cool. And just adjacent to the mountains are the Ossipee Pine Barrens. I could blindfold you and drop you in the middle of the woods and you wouldn't know you weren't in NJ.

1616973662195.png


1616973696156.png
 

Boyd

Administrator
Site Administrator
Jul 31, 2004
7,948
1,705
Ben's Branch, Stephen Creek
I think the site already has plenty of LIDAR imagery available for Southern NJ. If you want a map without the roads and other features, use the monochrome version.

I have been working on the waypoints module for the past couple weeks and have made good progress - I can import Garmin .gpx files, convert them to my own format and export them back out for Garmin. But it will take a number of weeks to put together all fhe pieces needed for the app. Making even more LIDAR maps of our small corner of the world just wouldn't be the best use of my time, sorry.
 
Apr 6, 2004
3,257
293
Galloway
I think the site already has plenty of LIDAR imagery available for Southern NJ. If you want a map without the roads and other features, use the monochrome version.

I have been working on the waypoints module for the past couple weeks and have made good progress - I can import Garmin .gpx files, convert them to my own format and export them back out for Garmin. But it will take a number of weeks to put together all fhe pieces needed for the app. Making even more LIDAR maps of our small corner of the world just wouldn't be the best use of my time, sorry.
I am immensely grateful for the imagery available, and I use the monochrome extensively. But the shaded maps go much further in giving a sense of elevation differences, especially when zooming out. I shouldn't be complaining though! The new additions have been a game-changer.
 
  • Like
Reactions: Boyd
Top