Crosshatch and ortho Processing

Data Processing - Discussion and Q&A
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Question lets say I flew two separate missions one being ortho at 200 ft and another being a complete replica at 200ft but being a crosshatch. What difference does it make if I just drop all the data combined (processing) ? or should it be done separately? will the data be more precise ? will the 3d model be cleaner?

let me know your thoughts!

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So one flight standard lawnmower pattern and then a crosshatch going both directions? Nadirs or obliques? GCP’s? If you pretty much caught the same thing twice then all it will do is add to processing time.

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That’s correct. Lawnmower pattern and crosshatch.Two separate missions.
During regular ortho it’s straight 90 down. And at the end it takes perimeter.
No GCP’s

I figured! Thank you

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That’s actually not a bad workflow for 3D modeling. If you had a mix of nadir and oblique on the same line then that is fine. Whether or not you need the perimeter depends on the subject. It’s great for “orbiting” a structure but can actually cause problems on something like a large jobsite because of the way they determine heading and pitch. The further you get away from the centroid of the project the higher the pitch and you’ll start getting very distant objects in the view.

If I run this workflow I use our standard 80/65 nadir and set the Enhanced 3D to 65/65. If I am just using the Enhanced 3D I use 75/75 for dense areas and 70/70 for big wide open tracts. Just think of how often it is going to have to shoot to get 3-4 images of every vertical face. This also helps keep the image count manageable.

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Generally for land surveying without GCPs, I’ll carry out a ‘lawnmower’ and then a perimeter to help reduce or even eliminate the bowling effect. The perimeter obliques capture a wider area of land to help flatten it out.

If I’m only after an orthomosaic image, without any consideration for the elevation all values, then quite often the obliques can be removed.

If a half decent 3D model is required, ‘crosshatch’ is a must if you’re wanting to do it using an automated method, BUT, be aware that the elevation all values won’t be as accurate. No harm in processing two maps however. One for accurate z-values and another for prettiness. :+1:

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