GPS referenced pointcloud

[LukeF]

Hi everyone,

We have a BLK360 and use it regularly for scans and photogrammetry work. Up until this point we have not had to apply a control and use GPS coordinates.

I do not come from a surveying background so my understanding of some areas is limited.

I'm looking to understand how applying GPS coordinates will affect the point cloud. Firstly I understand (correct me if Im wrong) that we need a few georeferences makers within the point cloud visable from multiple scan points. The XYZ data then needs to be fed to Register360 via text file in "Point#, Northing, Easting, Elevation,Comment or Point#,Y,X,Z,Comment" format. And that this will apply a control to the entire cloud.

1. Does this mean that If I now select random points from the point cloud it will give me each of those individual points lat,long,height?

2. If I provide the client with a LGS file and they create a GEOTAG by clicking on a single point. Will that point display its lat/long/height?

or

3. Does adding the GPS only affect the position of the entire cloud. I.e if the client places the data it in a separate software if would be geographically correctly positioned?

[gsisman]

Hi everyone,

We have a BLK360 and use it regularly for scans and photogrammetry work. Up until this point we have not had to apply a control and use GPS coordinates.

I do not come from a surveying background so my understanding of some areas is limited.

I'm looking to understand how applying GPS coordinates will affect the point cloud. Firstly I understand (correct me if Im wrong) that we need a few georeferences makers within the point cloud visable from multiple scan points. The XYZ data then needs to be fed to Register360 via text file in "Point#, Northing, Easting, Elevation,Comment or Point#,Y,X,Z,Comment" format. And that this will apply a control to the entire cloud.

1. Does this mean that If I now select random points from the point cloud it will give me each of those individual points lat,long,height?

2. If I provide the client with a LGS file and they create a GEOTAG by clicking on a single point. Will that point display its lat/long/height?

or

3. Does adding the GPS only affect the position of the entire cloud. I.e if the client places the data it in a separate software if would be geographically correctly positioned?

Luke,
Bottom line. Get a surveyor to set up your control.

Either before with targets, or after you scan and can pick specific, very identifiable items that can be shot or RTK GPS'ed after the fact.
We've done both. Scan Targets with reflectorless Total station measurements work best. The total station can be set on RTK or RTN based control points.
GPS will allow you to place the Entire registered scan cloud (Multiple setups) in REAL_WORLD Coordinates using Projections (Project real-world spherical GPS/Lat Long & Ellipsoidal to a flat plane)

Your BLK360 TLS scanner would be registering scans together in a "Plane-type environment" different than a Mobile mapping that is calculating trajectories and many other variables guided by GPS and other IMU sensors and over very large distances usually.
You would have to bring this registered "Flat Plane Scan cloud" into a piece of software that you could switch back to Spherical coordinates like GPS coordinates, which technically are x,y,z (the Z being ellipsoidal height). That could then be converted to Lat, Long and ellipsoidal height or Ortho Height (Sea Level) based on a specific Geoid Model you would apply.

[BrentPeter]

Applying GPS coordinates to the point cloud will enable you to extract the latitude, longitude, and height information for individual points within the cloud.

If the client creates a GEOTAG by clicking on a single point in an LGS file, it should display the lat/long/height for that specific point.

Adding GPS coordinates affects the position of the entire point cloud, ensuring it is geographically correctly positioned when imported into other software.