Lidar scan ECW file places site in Antarctica when imported.

[jsaayman]

Hi

I've converted a ECW file to a RCP file so I can import it into Civil 3d, but when I import the file the site coordinates place the site in Antartica. The Lidar scan was done over an area over the Witwatersrand in South Africa. 

I can't figure out what I'm doing wrong in the conversion on Recap or could it be the why that I'm setting up my Civil 3D file before I attach the survey to the drawing. 

If anybody has had a similar problem and found a solution, please help. 

[ChicagoLooper]

Hello @jsaayman 

You'll need to specify the ecw's native coordinate system in Recap. The native coordinate system of the ecw was given to the ecw by the original author so you need to accurately determine what it is--no guessing is allowed. Then you'll need to assign a coordinate system to the modelspace of your drawing. 

If you assign the same coordinate system to modelspace as the ecw, you'll be fine. 

However, if you decide you want to use a DIFFERENT coordinate system than the ecw then you'll need to perform a transformation so AutoCAD can transform the ecw's CS to your modelspace's CS. 

The fastest and easiest way to resolve your issue is to upload your file (or provide the a downloadable link) so the forum can evaluate the ecw. Also, do you know what coordinate system you would like to use for Witwatersrand?  

[Pointdump]

Hi Juan-Emil,
How did you import your ECW into ReCap? I don't see that format as an option.
As @ChicagoLooper says, give us a link to your data and one of us will figure out how to get it into your C3D drawing.
Dave

[jsaayman]

Hi Dave

Sorry, I miss recall now that the I requested the surveyor provide me with a laz file so I could import it into Recap.

The files are to big to upload here so please download them from my google drive. 

https://drive.google.com/file/d/1iFi5gd63qgalkhVUYsG7K6B8xahnvk_0/view?usp=sharing

https://drive.google.com/file/d/1GSD4T4aWYCZsfkABsSM4SgH1QRo2eHeC/view?usp=sharing

[jsaayman]

The Survey system that the ECW file was done on was the WGS84 Hartbeeshoek 94 reference.

[Pointdump]

Juan-Emil,
While waiting for ReCap to process that large LAZ file, I drag-n-dropped the ECW into QGIS. QGIS shows EPSG:2052, and then drops it into the sands of Egypt.
OK, ReCap finished processing the cloud, using Hartebeesthoek94.Lo27 (EPSG:2052) and Civil 3D also places it in Egypt.
At this point we're just guessing what coordinate system to use. I'll check ESRI:102566 Hartebeesthoek94 Lo27 (E-N), but I really think you'll want to make a phone call to verify exactly the coordinate system. Try to get an EPSG or ESRI number or WKT file if it's a custom coordinate system.
Dave

[Pointdump]

OK, I figured it out. Both Point Cloud and ECW Image are in ESRI:102566 Hartebeesthoek94 Lo27 (E-N) Coordinate System. Unfortunately that CS is not in MAPCSLIBRARY. Normally it's a quick add, but South African Coordinate Systems are quirky. I'll play with it.
Dave

[ChicagoLooper]

Hi @jsaayman and @Pointdump 

Both the ECW image and the LAZ points were evaluated in Global Mapper. The projection used in Global Mapper was UTM84-35S, meters. 

LAZ points:

The points are projected to Transverse Mercator, Hartebeesthoek 1994 datum with NORTH orientation, meters.

ECW imagery:

The image is projected to Transverse Mercator, Hartebeesthoek 1994 datum with SOUTH orientation, meters. The south orientation is the issue and needs to be changed. See image-1.

Image-1. Global Mapper has both North and South orientations of the Transverse Mercator.

When the ECW's projection is changed from south to north the ECW inserts correctly. See image-2.

Image-2. Note: World Imagery is shown in the background for reference.

The LAZ point cloud is projected correctly. It's using Transverse Mercator, Hartebeesthoek 1994 (north orientation), meters or EPSG 2052. No modifications to the projection are needed so it inserts correctly against GloMap's UTM84-35S coord assignment. Once the ECW's projection is corrected, it can be inserted along with the LAZ points. See image-3. 

Image-3. Both the ECW image and LAZ point are inserted . the background is world Imagery.

Additional notes:

• Couldn't index the LAZ points in Recap, it hangs at 75%. 
• Couldn't add the ECW imagery to C3D using a data connection.
• Couldn't add the ECW image to C3D using MAPIINSERT.
• The image has an irregular shape. I would suggest cropping it smaller and making it a rectangle. AutoCAD doesn't like irregular shapes. 
• South Africa coordinate systems are whacky. Is it possible to get someone (or something) to re-project the points to another coordinate system. I would recomment a world coordinate system such as WGS84.PseudoMercator, meters (EPSG 3857)?

[Pointdump · Accepted solution]

Juan-Emil,
Here you go. Custom Coordinate System created. >>>ESRI:102566 Hartebeesthoek94 Lo27 (E-N)<<<. Use Command MAPCSLIBRARYIMPORT to import the new CS into your MAPCSLIBRARY. ReCap draws its Coordinate Systems off of MAPCSLIBRARY, so you can use both the ECW and the LAZ files in Civil 3D.
Dave

[jsaayman]

Thank you @ChicagoLooper and @Pointdump for your help. I’m going to try with you suggested solutions tomorrow and then I’ll accept the solution.