Trimble Business Center

Using DJI UAV Images in Station View, Capturing 3D overlays

Hello All,

I have been playing around with determining the position of images taken with a DJI UAV. I would like to create some very high-quality images which will be a hybrid of aerial imagery and the 3D model inside of TBC.

I think this would really help with client interaction, public engagement and quality control for our site. Long term I would like to implement .IFC files into the mix as well.

So far, my process is as follows:

Determine position information of the UAV image

•         The EXIF data contained within the JPEG files contains the require information for positioning the image in 3D space.
•         As far as I can tell the image rotation (GimbalYawDegree) is measured from "magnetic North" so needs to be corrected to grid.
•         The gimbal angle (GimbalPitchDegree) seems to be measure from 90° with the horizon (Where 0° is straight down and 90° if flat looking at the horizon).
•         The RTK corrected position is given in L,L,H which TBC can easily convert to E,N,Elv.
•         The resolution of the image is also important for scaling (this is a problem in TBC currently).
•         From this information I can determine that the cameras position was E:441856.77, :210243.55, Elv 171.05, Rotation from Grid North: 134°26'00", Angle Down: 65°12'00" (90°-24.8°)

Create a photopoint station in TBC

•         This process is a pain, you cannot create a photostation from a typed in coordinate. I found that I can export a single point as a LAS point cloud and re-import.
•         When you re-import TBC creates a "ScanStation" at the points location which can be used with the station view function.

Create a station view and attempt to match the image angle

•         The "ScanStation" can now be used in the station view.
•         Using the 3D view settings, I can attempt to match the horizontal and vertical angles of the image.
•         The issue I face is one of scaling, zooming in and out changes the perspective of the 3D model.
•         It will only match the UAV image at 1:1 scale and TBC does not tell you the zoom level in this view. Nor does it allow the view to be set to a fixed size (i.e. the resolution of the image 8192x5460).

The end result is the 2 perspectives do not quite match, you can get them close but not 100% perfect. I think the gimbal pitch may be a little off as well but it is hard to tell. Can anyone think of a better workflow than this?

Feature Requests/ Enhancements

•         It would be great if we could import a UAV image and have TBC read the XMP data and treat the image like a photo station in the same way it does for SX12 data for example. It would be nice if this feature was not bundled into the photogrammetry module as it is really just reading a text file.
•         Allow better control in the 3D station view, set a zoom level to match that of the image. Better yet allow the window to be resized to that if the image (8192x5460 in this case). Also it could read the camera lens size and aperture. That way when a capture of the model is created the user can overlay the 2 in photoshop with minimal effort.
• Getting a smooth workflow for the above would be great for visualisations of 3D models augmented into the real world. Clients often want to see how the design will sit in the land and the drone images bring it to life.

Open to any suggestions/ things I have missed!

Thanks for your help.

Sam

Hi Sam,
congrats on this amazing work. 
From the development with the photogrammetric images we already did have a discussion about how to integrate the drone images as photo stations into TBC. 

Concerning your approach there are a few mistakes. The EXIF information is the orientation of the image BEFORE the adjustment, which means the X,Y,Z position can vary from 3cm to 10m.
The image rotation values are by far only approximations as they are created with low quality IMU systems in drones.
The gimbal angle varies from drone vendor to drone vendor and is unfortunately not standardized.

I will add the request to our feature list.

Original Message:
Sent: 04-12-2023 06:38
From: Sam Lemon
Subject: Using DJI UAV Images in Station View reading EXIF Data, Capturing 3D overlays

Using DJI UAV Images in Station View, Capturing 3D overlays

Hello All,

I have been playing around with determining the position of images taken with a DJI UAV. I would like to create some very high-quality images which will be a hybrid of aerial imagery and the 3D model inside of TBC.

I think this would really help with client interaction, public engagement and quality control for our site. Long term I would like to implement .IFC files into the mix as well.

So far, my process is as follows:

Determine position information of the UAV image

•         The EXIF data contained within the JPEG files contains the require information for positioning the image in 3D space.
•         As far as I can tell the image rotation (GimbalYawDegree) is measured from "magnetic North" so needs to be corrected to grid.
•         The gimbal angle (GimbalPitchDegree) seems to be measure from 90° with the horizon (Where 0° is straight down and 90° if flat looking at the horizon).
•         The RTK corrected position is given in L,L,H which TBC can easily convert to E,N,Elv.
•         The resolution of the image is also important for scaling (this is a problem in TBC currently).
•         From this information I can determine that the cameras position was E:441856.77, :210243.55, Elv 171.05, Rotation from Grid North: 134°26'00", Angle Down: 65°12'00" (90°-24.8°)

Create a photopoint station in TBC

•         This process is a pain, you cannot create a photostation from a typed in coordinate. I found that I can export a single point as a LAS point cloud and re-import.
•         When you re-import TBC creates a "ScanStation" at the points location which can be used with the station view function.

Create a station view and attempt to match the image angle

•         The "ScanStation" can now be used in the station view.
•         Using the 3D view settings, I can attempt to match the horizontal and vertical angles of the image.
•         The issue I face is one of scaling, zooming in and out changes the perspective of the 3D model.
•         It will only match the UAV image at 1:1 scale and TBC does not tell you the zoom level in this view. Nor does it allow the view to be set to a fixed size (i.e. the resolution of the image 8192x5460).

The end result is the 2 perspectives do not quite match, you can get them close but not 100% perfect. I think the gimbal pitch may be a little off as well but it is hard to tell. Can anyone think of a better workflow than this?

Feature Requests/ Enhancements

•         It would be great if we could import a UAV image and have TBC read the XMP data and treat the image like a photo station in the same way it does for SX12 data for example. It would be nice if this feature was not bundled into the photogrammetry module as it is really just reading a text file.
•         Allow better control in the 3D station view, set a zoom level to match that of the image. Better yet allow the window to be resized to that if the image (8192x5460 in this case). Also it could read the camera lens size and aperture. That way when a capture of the model is created the user can overlay the 2 in photoshop with minimal effort.
• Getting a smooth workflow for the above would be great for visualisations of 3D models augmented into the real world. Clients often want to see how the design will sit in the land and the drone images bring it to life.

Open to any suggestions/ things I have missed!

Thanks for your help.

Sam

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Sam Lemon
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