How to add points onto a point cloud

[RSGlaciers]

Hello Cloud Compare users,

I need some help! I am a MSc student using Cloud Compare for the first time. I have version 2.3, and could update to the latest version if needed.

I have opened a .las file point cloud in cloud compare. What I need to do now is add data points onto the point cloud. To provide some context, the points represent areas on the point cloud where geometric changes occurred after the laser scan took place. These events are attribute data essentially, that were recorded using a time-lapse camera that was pointed towards the same location as the laser scanner. The point cloud is just a snap shot in time, and reflects a single geometry (we had one hour of decent weather and managed to scan a mountain slope with a landslide potential), but my time-lapse photos show geometric changes taking place all day (as they continued to film the mountain from morning to night), and I need the real world co-ordinates for all the events that occurred, which is why I am using a point cloud.

I would like to extract the co-ordinates (x,y,z) of all the points that I add to the point cloud, and I need to measure the meter scale distances between each point, and save this data.

Does Cloud Compare have spatial analysis functions? I would like to perform some kind of cluster analysis to determine whether the individual points that I wish to add to the point cloud are clustered in space / time. This is sometimes called a hotspot analysis. Secondly, I would like to perform a proximity analysis - I want to find out whether there are common distances between each data point - for example, are most data points separated by 10 metres? or 30 metres? Can I do these things using cloud compare?

In the mean time I will look for tutorials on using cloud compare. Any advice would be really appreciated. Thanks everyone!

Ricky

[daniel]

Hi,

I'm not sure to understand what you additional points look like. But if they are proper 3D points (or point clouds) then you can indeed align them with the las cloud. And eventually merge them.

Don't hesitate to post snapshots if I missed something.

And last but not least you should definitely upgrade to the latest version (2.6.3.beta) as the alignment / registration tools are much more powerful.

[RSGlaciers]

Hi Daniel,

Thank you for your message. I have attached a screen shot image of the point cloud I am using. You will see there are some pink coloured points - these are the points I have manually added on top of the point cloud. I did this by clicking on "point picking", and then clicking on a point on the cloud.

[RSGlaciers]

Also, I am running mac 10.6.8

do you have the link so I can upgrade / download to 2.5.4 version cloud compare? I believe this is the latest version my 64 bit machine can support.

[RSGlaciers]

Also - is it possible to export the points (you seen them above in the colour pink) as a shape file?

If the answer is yes, I could then import the shape file into ArcGIS.

[daniel]

Ok I understand. When you pick a point the info appears on the screen thanks to what we call a 'label'. You can attach labels to any point of a cloud but it's always a manual process.

Therefore you could load you additional points from a separate file, but then you would have to pick each point separately (you can use the SHIFT + left click shortcut to do this faster without using the 'Point picking' tool). Another possibility would be to change the size and color of the additional cloud.

And to export the points you pick yourself, you can use the 'Point list picking' tool to create a new point cloud from your selection (see http://www.cloudcompare.org/doc/wiki/in ... st_picking). Then you can export this cloud as a SHP file.

However it will probably only work with the most recent versions of CC(2.6.2 or 2.6.3.beta). There will be an update for Mac OS next month (but I'm not sure if Mac OS 10.6.8 will be supported). You'd better get a hand on a Windows machine ;)

[RSGlaciers]

Hi Daniel,

Thank you for your answer. I have a new question:

Does Cloud Compare allow you to view digital photographs, and draw polygons onto digital photographs?

Ricky

[daniel]

Well you can load any standard picture (but it will be displayed as a texture rectangle with pixel coordinates). Otherwise you can load calibrated pictures (output by Bundler).

And then there's a trick to draw polylines with the Graphical Segmentation tool (the scissors icon) that lets you draw and export pseudo-2D polylines. 'Pseudo' because they are 2D polylines re-projected in 3D (at an arbitrary distance).

What kind of polyline are you looking for exactly? 2D or 3D?

[RSGlaciers]

Hi Daniel,

Thanks for your answer.

I'll try to explain in more detail my project.

I have digital photographs of a glacier (see photo attached). I took the photos using a camera. Positioned next to the camera my Professor had the laser scanner. So, I want to use the point cloud to determine the x,y,z co-ordinates of specific objects in the photos (ice falling off the glacier into water).

I could make the polygons in Adobe Photoshop (again see photo where I do this to show you)...but...I would need to import the polygons into Cloud Compare and label the polygons onto the point cloud to get co-ordinates

Alternatively, I would rather draw the polygons directly onto the point cloud and save the polygons (and their co-ordinates in 3D, x,y,z).

Does that make sense to you?

[RSGlaciers]

So I hope you see

1. i have a point cloud registered in UTM coordinates (eastings, northings)

2. I have digital photographs of glacier

3. I want to calculate the size of the ice inside the polygons to create categories eg. small, medium, large

4. questions - what software to draw the polygons? - how to import the polygons onto a point cloud?

This feels like a 2D to 3D shift problem

photo pixel coordinates - real world coordinates ??