Defra Survey Data - LIDAR

[MethodDesign]

On 8/10/2023 at 9:10 PM, Rebecca R said:

Tha

Hi @Tom W., thanks for responding.

 

I've downloaded the  'LIDAR Composite DTM 2022 1m Index' option but I'm not sure which bits to import or how (see attached images for options).  Are you able to advise please?

 

And yes, I've had similar experiences with Georeferencing Point Clouds so far, although this has been the only Defra data that I've actually successfully made a model of so far!

 

Thanks.

 

Hi @Rebecca R, 

It looks like the data you downloaded includes a 1m resolution DTM in .tif format. You can use QGIS (open source GIS software) to extract a set of contour lines in .shp format from the DTM (Raster > Extraction > Contour..., choose DTM as input layer and specify contour interval in metres). The output .shp will contain two automatically generated data fields: a numeric ID for each contour, and an Elevation value. The .shp can be imported into Vectorworks, appearing as a set of 2D polys with an attached record format. You can then select the polys and use Tools > Records > Modify by Record... > Elevate 2D Polys to convert them to 3D polys as suggested by @Tom W.. (Make sure you set the Record Field to Elevation when doing this, otherwise it will interpret the unique numbers in the ID field as the elevation data, and the results will make no sense at all). You can then select the 3D polys and create a Site Model from Source Data...

You'll probably want to experiment with the contour interval in QGIS to achieve the right balance of detail & file size. After creating the .shp you can also use Vector > Geoprocessing Tools > Clip... to crop the results down to a smaller coverage area. For this you'll need a separate .shp file containing a rectangle/polygon defining the Clip area, which you can create in Vectorworks or QGIS.

After importing your contour .shp into Vectorworks you might also need to reduce the vertex count, using Modify > Drafting Aids > Simplify Polys... (before or after elevating the polys) so the resulting site model doesn't get too heavy and slow.

If your drawing is set up and all files imported correctly in terms of Georeferencing, Origin etc., your site model will be at its true geographic scale and location, and the Use Geoimage Texture option in the Site Model Settings > 3D Display tab should work.  

  
  

Edited December 7, 2023 by MethodDesign
Clarity

[Rebecca R]

On 12/7/2023 at 10:10 PM, MethodDesign said:

 

Hi @Rebecca R, 

It looks like the data you downloaded includes a 1m resolution DTM in .tif format. You can use QGIS (open source GIS software) to extract a set of contour lines in .shp format from the DTM (Raster > Extraction > Contour..., choose DTM as input layer and specify contour interval in metres). The output .shp will contain two automatically generated data fields: a numeric ID for each contour, and an Elevation value. The .shp can be imported into Vectorworks, appearing as a set of 2D polys with an attached record format. You can then select the polys and use Tools > Records > Modify by Record... > Elevate 2D Polys to convert them to 3D polys as suggested by @Tom W.. (Make sure you set the Record Field to Elevation when doing this, otherwise it will interpret the unique numbers in the ID field as the elevation data, and the results will make no sense at all). You can then select the 3D polys and create a Site Model from Source Data...

You'll probably want to experiment with the contour interval in QGIS to achieve the right balance of detail & file size. After creating the .shp you can also use Vector > Geoprocessing Tools > Clip... to crop the results down to a smaller coverage area. For this you'll need a separate .shp file containing a rectangle/polygon defining the Clip area, which you can create in Vectorworks or QGIS.

After importing your contour .shp into Vectorworks you might also need to reduce the vertex count, using Modify > Drafting Aids > Simplify Polys... (before or after elevating the polys) so the resulting site model doesn't get too heavy and slow.

If your drawing is set up and all files imported correctly in terms of Georeferencing, Origin etc., your site model will be at its true geographic scale and location, and the Use Geoimage Texture option in the Site Model Settings > 3D Display tab should work.  

  
  

Thanks @MethodDesign, very kind of you to provide such a detailed response.  I've moved on from this project now for the time being at least and I'm not familiar with QGIS but I'll certainly look into this if the issue arises again, which I'm sure it will.  Great to have the very informative thread here to refer back to.  Thanks again!

[Amanda McDermott]

On 8/10/2023 at 6:56 AM, Tom W. said:

On Georeferencing Point Clouds I personally have found it very problematic. If I import a Point Cloud into a Georeferenced file the data comes in at the correct location but half of it is missing (it has pronounced linear bands where points are missing).

Interested to note this on looking back at this thread - we have had problems with a site model recently that turned out to be this same issue (we didn't know why we had those linear bands, but they were there and causing issues). Had thought it was possibly to do with our DXF export from GIS, but have established that's not it, the same data comes in fine to BricsCAD.

 

@Katarina Ollikainen I can't find Marketa here to tag, I'll email her with this but if you know her handle to tag her, it's she who has been helping us with this. I think we need to make sure whoever is the right person behind the scenes knows that this is not just our issue, please!

 

You can see in the screen shots here, the linear bands cut across everything and cause very weird things in the site model when we created it from the data without realising they were there!

[Marketa Hermova]

@Amanda McDermott thank you for the email and the follow up on your internal processes with regards to the export to DXF and import of DXF files to VW. I will address this internally and will follow up afterwards. For now, please use the workflow we discussed in our last meeting to clear the lines up.

[Amanda McDermott]

1 minute ago, mhermova said:

@Amanda McDermott thank you for the email and the follow up on your internal processes with regards to the export to DXF and import of DXF files to VW. I will address this internally and will follow up afterwards. For now, please use the workflow we discussed in our last meeting to clear the lines up.

Thanks Marketa - I'll note your user handle for next time!

[Jeff Prince]

On 12/11/2023 at 3:35 AM, Amanda McDermott said:

we didn't know why we had those linear bands, but they were there and causing issues

 

This typically happens when you import the LiDAR prior to setting the internal origin to a location within the extents of the LiDAR coverage.

The whole "long ways from the origin" problem that creates many issues for Vectorworks in regards to 3D.

I wonder if that is what @Marketa Hermova advised you on since the solution is not apparent in the thread.

[Amanda McDermott]

We did have the origins carefully set up... the advice was that we needed to isolate the lines and delete them prior to site model creation.

[Marketa Hermova]

Hello @Amanda McDermott and @Jeff Prince,

 

We are making some improvements as part of the Update4 that should help to resolve this. The Update4 is due to be released in a mid-March, please feel free to reach out to me if you keep having problems with the linear geometry/DXF import.