Georeferencing multispectral imagery

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

Hi all,

I am a researcher and I am working with multispectral camera using UAVs. My problem is that our images are not georeferenced so I can not create the   Ag Multispectral template. However, I have arround 500.000 points (x,y,z) that belong to this area and were registered with a GPS station. My question is how could we use these points like a set of GCPs points to reference all these images? and if I got it how could we create the AG Multispectral template when we have no georeferenced images until we loaded the other points?

Thanks in advance,

J.M.

2

Hi Francisco,

This is expected since the Ag Multispectral template is using the Alternative calibration method. The Alternative calibration method requests the images to be geolocated. 

There would be two ways to solve this:

  1. Simply opt for Standard calibration method over the Alternative:

  1. Create a file with the images coordinates that you can further import in the software. Please see: https://support.pix4d.com/hc/en-us/articles/202560019#gsc.tab=0 

Cheers,

Ina

3

Hi Ina,

I have the same scenario as Francisco with non-geotagged NIR images.

I am now processing my images using the AG multispectral template and standard calibration.

Next question is whats the recommended procedure for implementing ground control targets on the resulting point cloud?

 

4

Hi Ben,

The difference between adding GCPs in an RGB project vs an MSP one is that for the multispectral project the GCP’s needs to be marked in each band for each image. E.g. in a Sequoia MSP project if the GCP is marked in an image of the Green band, it will also have to be marked in the Red, Red edge and NIR images that correspond. Hence, what would be one mark in an RGB project results in four marks in a Sequoia multispectral project. In addition, you have to mark your GCP in at least 3 sets of images. Therefore, there should be at least twelve (3*4marks) for each GCP in the project. Once all GCPs are added, click Process > Reoptimize to apply the changes. 

For full procedure see: https://support.pix4d.com/hc/en-us/articles/202560039-How-to-add-import-GCPs-in-the-GCP-MTP-Manager#gsc.tab=0  

Cheers,

Ina