Community 3.3.6

[addisonpletcher]

Hi there,

I'm wondering how Correlator3D calculates the resolutions of DSMs, specifically the "maximal" option. I've found that it is close to a manually calculated ground sampling distance for my flight, but can't find any information in the documentation beyond that it "takes into account the project parameters (i.e. image resolution, altitude, focal length, etc.)".

Bottom line, I'm wondering if the calculated "maximal" DSM resolution is equivalent to GSD.

Thanks!

[Sean Mcintyre]

Hello addisonpletcher,

Yes, I can confirm that when selecting the "maximal" option it would be considered a one-to-one DEM resolution, which corresponds to your maximum GSD.

We usually never require that resolution for our DEMs, I also like to avoid long processing times so we typically input the resolution equivalent to 2x or 3x our max GSD for the specific sensor we are processing.

I hope this helps!

SM

[David Alamillo]

Hi Sean and Addison,

Absolutely! The resolution you choose during the DEM creation process has a direct correlation to your GSD. For your upcoming projects, it's important to keep in mind that the default "optimal" resolution is set to five times your maximum GSD. As a general guideline, we typically recommend using a factor of three times the maximum GSD for most projects.

Best regards,

[addisonpletcher]

Thanks so much for that information! Along those same lines, how is the "optimal" resolution during orthorectification calculated? For my project's purposes we are using 2x GSD for DSM resolution, and straight GSD for orthorectification - following the reasoning provided, it would make sense that the ortho resolution would be equal to the GSD. However, in some processed projects this is not always the case (ie 10 cm x2 - 20cm DSM resolution, but orthomosaic resolution is 12cm rather than 10, which is what one would expect). Is Correlator3D dynamically adjusting the ortho resolution based on DSM quality, image overlap, or resampling algorithms, etc., rather than strictly enforcing the software calculated maximum GSD?

Thanks so much!

Addy

[Sean Mcintyre]

Hi Addy,

Sure, happy to help! I believe you are correct the software calculates the optimal resolution automatically based on the ground sampling distance of your imagery. However, have you tried inputting the value manually?

Best,

SM

[addisonpletcher]

Yes, I am able to manually enter a resolution, but I'm more so wondering the how Correlator3D determines the "optimal" resolution during the orthorectification step. I've found that it often matches the "maximal" option for DSM generation (ie GSD), but not always (indicating it is calculated differently).

Thanks!

Addy

[David Alamillo]

Hi Addy,

The optimal resolution for orthorectification corresponds to the project's ground sampling distance (GSD). In DSM generation, the "maximal" option also represents the highest resolution achievable from the imagery for triangulation, which typically aligns with the GSD. Any slight differences between these values arise because, at the orthorectification stage, the GSD can be assessed more precisely using a high-accuracy DEM—something not yet available during DSM generation, creating a classic chicken-and-egg problem.

Best regards,

David