Creating a surface from a point cloud using Recap

[cneelyUFTR2]

I used Recap, converted the point cloud from UTM 14 to TX83-NCF. I made sure the project settings were set to foot. I inserted the point cloud, and it dropped in the wrong location. If I select it, the properties show meters instead of feet. I can change the scale in the properties to 3.28 and its moves to the correct location. Is that enough to get a spatially accurate surface?

[Pointdump]

Hi Charlie,
You shouldn't need to do any scaling to take your point cloud through ReCap and into Civil 3D. Can you zip together and post your point cloud and drawing?
Dave

[ChicagoLooper]

Hi @cneelyUFTR2 

Instead of converting the Point Cloud to UTM 14 to TX83-NCF, make sure it's using the original projection given to it by the PC's creator, such as the drone pilot. Whatever the pilot used to project the PC, should be verified in Recap. You need to verify because Recap might go rogue and give it a wrong coordinate system projection. You might have to ask the pilot what was used during the flight. For example, the pilot might have used Pseudo Mercator WGS84, meters (EPSG 3857). You need to honor this projection.

Next, back in your drawing, you may assign Texas State Plane,  NAD83, the appropriate ZONE, feet. Or you may assign UTM83 and zone. Add your Point Cloud after you've established modelspace's assigned coordinate system.

Finally, turn on Bing Hybrid to see how the aerial imagery compares to your Point Cloud.

[cneelyUFTR2]

The original projection is UTM14 meters. The data is from TNRIS. 

[ChicagoLooper]

Two questions:

1. Can you post provide the Site, web page, so the Point Cloud can be download (what's the name or ID code for the point cloud)?
2. What coordinate system did you assign to modelspace?

If the forum can replicate the issue, then a feasible solution can be provided.

[cneelyUFTR2]

Here's a link to the files I used. 

LiDARPointClouds.zip
Password: 935CBcjpM2Zq
https://fileshare.eikoncg.com/dl/6Co2LN1wB5

[ChicagoLooper]

Hi @cneelyUFTR2 

OK, try this.

1. While in Recap, make sure you verify the native coordinate system of the Point Cloud which is UTM83-14, meters.  This is the NATIVE coordinate system of the Point Cloud, not the coordinate system you want to use in C3D.(Image-1)

Image-1

2. Then in Civil3D, assign UTM83-14F, then insert the Point Cloud. Insert it at 0,0 (do NOT click in modelspace!!) and make sure to apply scale=3.2808 (Image-2). 

Image-2.

3. Turn on Bing Hybrid and compare aerial imagery to the rcp file.

[ChicagoLooper]

Hi @cneelyUFTR2 

Point cloud in modelspace (UTM83-14, feet).

Zoomed-in to Sam Houston High School.

[ChicagoLooper]

Hi @cneelyUFTR2 

OK, using your linked file from Post #6......

LiDARPointClouds.zip
https://fileshare.eikoncg.com/dl/6Co2LN1wB5

~usgs18-70cm_14SPC960320.laz

Recap settings like this:

Image-1

2. Civil 3D (UTM83-14F) insertion at 0,0 and scale=1.0 like this:

Image-2

3. Back in C3D, assigned coordinate system is UTM83-14F.

Image-3

4. Zoomed-in to intersection of Dixie Rd. and Riley Rd.

Image-4

[Pointdump]

Charlie,
Thanks for posting your data. Using LASInfo in the free >>>LASTools<<< I get this:

usgs18-70cm_14SPC960320.laz
COMPD_CS["NAD83(2011) / UTM zone 14N + NAVD88 height
VERT_CS["NAVD88 height - Geoid12B (metre)
histogram of classification of points:
2150071 unclassified (1)
7174655 ground (2)
3585 noise (7)
134 water (9)
169 rail (10)

usgs18-70cm_14SPC960305.laz
COMPD_CS["NAD83(2011) / UTM zone 14N + NAVD88 height
VERT_CS["NAVD88 height - Geoid12B (metre)
histogram of classification of points:
4472873 unclassified (1)
6469928 ground (2)
9641 noise (7)
1120 water (9)
1048 rail (10)
1014 bridge deck (17)

You'll want to filter ground points before you can create a usable surface in C3D.
Automatic Ground Classification in ReCap 2023.1 works very well to give you only usable ground points.

In ReCap you'll set this:

Current: NSRS11.UTM-14 EPSG:6343
Target: TX83-NCF EPSG:2276

In Civil 3D you'll set Insertion Scale to US Survey Feet.

Dave

[ChicagoLooper]

Ah, yes....as @Pointdump has suggested,

In Recap, first import your LAZ.

Next, set the current CS of the Point Cloud and the Target CS here:

Then.....when you go to C3D, you can assign an SPCS projection instead of UTM.

Current=the native coordinate system of the point cloud

Target=the coordinate system to be assigned to Civil3D  modelspace 

!!Good one @Pointdump!!

[TerryDotson]

---

usgs18-70cm_14SPC960320.laz   ... 7174655 ground (2)

usgs18-70cm_14SPC960305.laz  ... 6469928 ground (2)

You'll want to filter ground points before you can create a usable surface in C3D.
Automatic Ground Classification in ReCap 2023.1 works very well to give you only usable ground points.

If the lidar data is already classified, why would you need the ReCap classification tool?

[Pointdump]

Hi Terry,
"If the lidar data is already classified, why would you need the ReCap classification tool?"
Automatic Ground Classification in ReCap doesn't just filter ground points. It also removes noise and mis-classified points.
Dave

[cneelyUFTR2]

Lots of good ideas. I've been away from this issue for the last few days but hope to re-visit it tomorrow and test out the suggestions.