Author Topic: LIDAR - Surface / Terrain Scanning  (Read 2861 times)

Offline Leclused

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LIDAR - Surface / Terrain Scanning
« on: January 22, 2016, 09:48:02 am »
Hello,

A while ago a member of our club found out that for Belgium Lidar surface/terrain data is available. He wrote an article about it on our blog

http://scavalon.blogspot.be/2016/01/virtueel-prospecteren-met-lidar.html

Especially the feature were you can look at the terrain with a hillshade is usefull for us cavers who do prospecting. It allows us to see nearly every depression on the surface from behind our computer. Even if this depression is situated in a forest. These depression are not visisble on photo's due to the trees but with lidar Terrain-Hillshade they become visible. In the application for the Ardennes we can add other layers such as ign cards/ river cards / aerial photo's / ..... and that makes it an incredible usefull application (for us Belgian cavers)

Of course this is not usefull for the UK. But it seems that something similar is available for the uk too.

https://environmentagency.blog.gov.uk/2015/06/16/free-mapping-data-will-elevate-flood-risk-knowledge/

More info on their portal : https://environmentagency.blog.gov.uk/2015/09/18/laser-surveys-light-up-open-data/

I did not check it in detail of how far you can go for the uk and which data is freely availabe. But perhaps I triggered some interest of some prospectors .... ;D ;D

Br


« Last Edit: January 22, 2016, 10:01:14 am by Leclused »
Dagobert L'Ecluse (SC Avalon - Belgium)
http://www.scavalon.be
http://scavalon.blogspot.be


Offline 2xw

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Re: LIDAR - Surface / Terrain Scanning
« Reply #2 on: January 23, 2016, 11:05:36 pm »
Its a good data release, the highest resolution is in cities and flood plains though and irritatingly a lot of limestone area is excluded - especially in the Peak where to my intense irritation the wntirety of castleton is covered by a 2m digital surface model which stops at the edge of Bradwell moor.

You can get Stoney Middleton at somat like a 2m terrain. You can layer cave surveys over it which made me particularly excited.

Offline RobinGriffiths

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Re: LIDAR - Surface / Terrain Scanning
« Reply #3 on: November 30, 2016, 05:08:46 pm »
Does anyone know if the English lidar data is available via a tile server endpoint(s)? The Wales ones are, which makes it easy to include in a maps mashup.

e.g. Welsh tileserver url: http://d3rykcmoi4kytu.cloudfront.net/lidar/latest/25cm_dsm/{z}/{x}/{y}.png   

Robin

Offline braveduck

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Re: LIDAR - Surface / Terrain Scanning
« Reply #4 on: November 30, 2016, 09:42:25 pm »
A few weeks back our community was kept awake for two hours after midnight
by a very low flying plane doing a LIDAR survey ,Criss Crossing a five mile square. :(

Offline RobinGriffiths

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Re: LIDAR - Surface / Terrain Scanning
« Reply #5 on: November 30, 2016, 10:36:41 pm »
I could probably google this, but in the spirit of informed discussion....  how do they manage to get the DTM - terrain as opposed to DSM - surface data? Trees and buildings gone in the terrain models.

Robin

Offline maxf

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Re: LIDAR - Surface / Terrain Scanning
« Reply #6 on: December 01, 2016, 07:07:04 am »
Much manual intervention. There are classifications for things such as trees and buildings. These are manually selected then flagged appropriately, they they can be included or excluded in files

Offline aardgoose

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Re: LIDAR - Surface / Terrain Scanning
« Reply #7 on: December 01, 2016, 10:27:34 am »
The env agency LIDAR data is available on a WMS tileserver at

 http://environment.data.gov.uk/ds/wms?SERVICE=WMS&INTERFACE=ENVIRONMENT--e9edb9f6-d563-4a5e-a425-c72c5eac919c

but I expect you know about that one, and it's probably not compatible with the mapping apis you are using.

Re filtering out trees etc, I understand the raw data has multiple return times for each scanned point, rather than just a single height as appears in the published DTM/DEM models.  Picking longest vs shortest returns helps filter out some of the clutter from forestry, etc.

I've used a combination of the OS 50m data, EA 2m LIDAR and some commercially obtained 5m LIDAR to create composite coverage DTM models for some of the Peak District, for use in my own 3d cave survey viewer, it would not be too difficult to create your own tiles and set up a server for it.  I used the GRASS package, a bit of a learning curve but script-able.  I think it has the facilities to create standard tiles built in.

Offline RobinGriffiths

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Re: LIDAR - Surface / Terrain Scanning
« Reply #8 on: December 01, 2016, 10:37:40 am »
I've been using Leaflet to do a mashup of OS 1:25,000 from Bing, NLS old maps, and Welsh Lidar.

I'll have a peep at the link.

Cheers,

Robin

Offline aardgoose

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Re: LIDAR - Surface / Terrain Scanning
« Reply #9 on: December 01, 2016, 10:58:18 am »

One of the things on my todo list, draping standard web tiles over a 3D model, currently I'm using a non standard tile mesh and have hand made OS map tiles. Ive looked at the NLS maps, nice but a shame the higher resolutions are chargeable.

You can have a look here:

https://aardgoose.github.io/CaveView.js/fulldemo.html

( 't' key is a shortcut to add the terrain, the peak master file is the best example)

Offline Leclused

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Re: LIDAR - Surface / Terrain Scanning
« Reply #10 on: December 01, 2016, 11:02:20 am »

One of the things on my todo list, draping standard web tiles over a 3D model, currently I'm using a non standard tile mesh and have hand made OS map tiles. Ive looked at the NLS maps, nice but a shame the higher resolutions are chargeable.

You can have a look here:

https://aardgoose.github.io/CaveView.js/fulldemo.html

( 't' key is a shortcut to add the terrain, the peak master file is the best example)

Nicely done  :thumbsup: Can I share the link to some others as example?
Dagobert L'Ecluse (SC Avalon - Belgium)
http://www.scavalon.be
http://scavalon.blogspot.be

Offline Graigwen

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Re: LIDAR - Surface / Terrain Scanning
« Reply #11 on: December 01, 2016, 11:14:43 am »

Re filtering out trees etc, I understand the raw data has multiple return times for each scanned point, rather than just a single height as appears in the published DTM/DEM models.  Picking longest vs shortest returns helps filter out some of the clutter from forestry, etc.



I believe this tree filtering to be very effective. I have been using the LIDAR scans for a Welsh research project since the summer, the largest previously unreported landform found was a 25m diameter 10m deep doline hiding in woodland.

The 2m LIDAR is available as an overlay on the Cambrian Cave Registry map http://www.cambriancavingcouncil.org.uk/registry/CCRm.htm
and can be overlain on the geology.

25cm scans are limited in coverage for Wales, coastal views show waves crests!

.

Offline TheBitterEnd

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Re: LIDAR - Surface / Terrain Scanning
« Reply #12 on: December 01, 2016, 11:59:01 am »

One of the things on my todo list, draping standard web tiles over a 3D model, currently I'm using a non standard tile mesh and have hand made OS map tiles. Ive looked at the NLS maps, nice but a shame the higher resolutions are chargeable.

You can have a look here:

https://aardgoose.github.io/CaveView.js/fulldemo.html

( 't' key is a shortcut to add the terrain, the peak master file is the best example)

Very good indeed!   :thumbsup:
'Never argue with a fool, onlookers may not be able to tell the difference.' — Mark Twain

Offline aardgoose

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Re: LIDAR - Surface / Terrain Scanning
« Reply #13 on: December 01, 2016, 12:04:20 pm »
Nicely done  :thumbsup: Can I share the link to some others as example?

Thanks,

Feel free to share, very much a work in progress, works in most modern browsers: Chrome/Firefox/Safari/Edge and IE11 including Ipads, although a bit heavy on memory consumption with terrain loaded.

I'm working on displaying routes through a cave (mostly working now), dye traced connections and survey station details.

The source is at https://github.com/aardgoose/CaveView.js if you like that sort of thing.

Cheers

Offline RobinGriffiths

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Re: LIDAR - Surface / Terrain Scanning
« Reply #14 on: December 03, 2016, 12:57:29 am »
Thanks aardgoose..

Flipping heck. Documentation is a bit missing, however, if you manage to find out what layer you want, then this works with Leaflet, English and Welsh versions -not got round to Scotland yet..

     welshLidarLayer = L.tileLayer('http://d3rykcmoi4kytu.cloudfront.net/lidar/latest/2m_{model}/{z}/{x}/{y}.png', { opacity: 1, zIndex: 6 })

enLidarLayer = L.tileLayer.wms('http://environment.data.gov.uk/ds/wms?SERVICE=WMS&INTERFACE=ENVIRONMENT--aace5ed3-2580-4c2e-bdd8-69b3d473d99d',
        {
            layers: 'LIDAR-{model}-TSR-2M-ENGLAND-EA-WMS',
            transparent: true,
            zindex: 6,
            opacity: 1
        });


where {model} is DSM or DTM