Point Cloud

[danielmacielw]

Does anybody knows whats sensors of phantom 3 Pro are capable to generate the point cloud? Where the drone gets this information from?

tnksss

 

[Meta4]

Does anybody knows whats sensors of phantom 3 Pro are capable to generate the point cloud? Where the drone gets this information from?

The Phantom can't generate a point cloud.
It just has a camera.
You can use software to create a point clout from a series of overlapping images taken by the camera.

 

[danielmacielw]

But where the phantom gets the height information?? how the drone knows its height? Is it by the baromether?

 

[Meta4]

But where the phantom gets the height information?? how the drone knows its height? Is it by the baromether?

If you upload your images to a service like DroneDeploy or if you use a program like Photoscan to do photogrammetry, the service or program uses the altitude stored in the exif info which is incorporated in each image file.

 

[quaddamage]

But where the phantom gets the height information?? how the drone knows its height? Is it by the baromether?

If you upload your images to a service like DroneDeploy or if you use a program like Photoscan to do photogrammetry, the service or program uses the altitude stored in the exif info which is incorporated in each image file.

Just to straighten things out:

To stabilize height during flight, Ph3 will use barometer which gives relative position with centimeter accuracy.

Inside EXIFs of the images, the drone will store less accurate position, but absolute, which comes from GPS.

If you are wondering whether the height information within EXIFs is correct - I often see HUGE errors in it, up to 50 meters. If this happens, I'm shifting all the values to something reasonable. Ground height for reference I'm getting from Google Earth - it's very inaccurate, but I wasn't able to find a fast way to get better height information.

ie. if I was flying at 100m, and ground height of my starting point in Google Earth is 60m, them I'm shifting all the Z coordinates to be around 160m.

 

[Richard R]

But where the phantom gets the height information?? how the drone knows its height? Is it by the baromether?

The barometer is used to determine and maintain height above the takeoff point. This is what is displayed in the app and used for things like RTH. The bird also reads the GPS altitude which is in altitude, defined as height above mean sea level (msl). Both are recorded in the exif file and can be used by processing systems like Drone Deploy or Maps Made Easy.

 

[Meta4]

Inside EXIFs of the images, the drone will store less accurate position, but absolute, which comes from GPS.

If you are wondering whether the height information within EXIFs is correct - I often see HUGE errors in it, up to 50 meters. If this happens, I'm shifting all the values to something reasonable. Ground height for reference I'm getting from Google Earth - it's very inaccurate, but I wasn't able to find a fast way to get better height information.

A long time back DJI used barometer data for altitude in Exif info but back in the middle of the P3 run, they changed to showing GPS (inaccurate) altitude as the main altitude reading in Exif data but barometer data is still in there somewhere.
Services like Dronedeploy or software like Photoscan look at both and work out altitudes without you having to do anything.

 

[quaddamage]

they changed to showing GPS (inaccurate) altitude as the main altitude reading in Exif data but barometer data is still in there somewhere.
Services like Dronedeploy or software like Photoscan look at both and work out altitudes without you having to do anything.

I don't know much about Dronedeploy workings, but for Photoscan - it only uses EXIF data when the picture is added to a project (I tried replacing the pictures later, and no change in Photoscan coords or cameras alignment occured). From the data, it fills "reference coordinates" of each camera. These "camera properties" can be fully exported to XML, modified, and re-imported back to Photoscan. Within exported XML file, there is no additional field for barometer height. This means it does not use anything beyond the X/Y/Z coordinates visible in "Cameras" list (but it calculates its own camera position using Least Squares Method or something similar).

Based on the above, I must say it seem unlikely that Photoscan uses barometer data. @Meta4, where have you seen that information?

 

[Meta4]

I don't know much about Dronedeploy workings, but for Photoscan - it only uses EXIF data when the picture is added to a project (I tried replacing the pictures later, and no change in Photoscan coords or cameras alignment occured). From the data, it fills "reference coordinates" of each camera. These "camera properties" can be fully exported to XML, modified, and re-imported back to Photoscan. Within exported XML file, there is no additional field for barometer height. This means it does not use anything beyond the X/Y/Z coordinates visible in "Cameras" list (but it calculates its own camera position using Least Squares Method or something similar).

Based on the above, I must say it seem unlikely that Photoscan uses barometer data. @Meta4, where have you seen that information?

I just know that Photoscan, DD etc, still manage to calculate good altitudes despite there being faulty GPS altitude data in the Exif info.

 

[quaddamage]

I just know that Photoscan, DD etc, still manage to calculate good altitudes despite there being faulty GPS altitude data in the Exif info.

I see, thank you for clarifying. I will try to check that when I have an opportunity.

 

[Meta4]

I see, thank you for clarifying. I will try to check that when I have an opportunity.

DroneDeploy have their own forum.
You could try asking there: DroneDeploy Forum

 

[danielmacielw]

Thank you very much everybody.. I think is important to know the takeoff point accurate informations (X/Y/X) in relation to the sea level to be able to manage this informations in other softwares that are capable to make a re-cassification of this data based on the takeoff point informations.

 

[Roamer105]

But where the phantom gets the height information?? how the drone knows its height? Is it by the baromether?

VPS, Barometer and GPS.

 

[Richard R]

Thank you very much everybody.. I think is important to know the takeoff point accurate informations (X/Y/X) in relation to the sea level to be able to manage this informations in other softwares that are capable to make a re-cassification of this data based on the takeoff point informations.

The maps made easy app, map pilot, takes a reference photo before taking off during a mission. Their software then uses the data in the exif file to calibrate/reconcile the GPS info with the local height data.