Orthophotos Improved Using Fake Ground Control Points

hello everybody my name is mike williamson and what i want to show you today is the benefit of using ground control points and if you don't have ground control points using fake ground control points instead of using no ground control points so the real ones are always better but if you don't have real ones to use i want to show you what using fake ones can correct so what i'm using today is web odm that's my my mapping program of choice it's uh the right price and uh one of the nice things about the unit user interface is that it gives you the ability to to show and open street maps image and overlay your ortho image on top of it so what i'm using these for is to compare with the the lining up of things like the cart path and and uh various points of interest to see how they how they line up with open street maps when you're comparing the ortho that hasn't had any ground control points versus the one that has had ground control points even though they were faked so i'll take you in here and show you what one of the parts of the golf course where the differences show up quite a bit is down by this screen and i'm going to take it down to about 50 and you can see how things like the bunkers don't line up the cart path doesn't line up the pump station over here doesn't line up so you can see where it's pretty squirrely but when you look at it from the overall perspective it really doesn't look bad now trying to line these things up later is going to be a challenge so i thought well let's i didn't gather any ground control points to start with and what i wanted to do was use a kind of a combination of google earth pro to be able to locate some points of interest identify their latitude longitude and elevation and use those as actual uh ground ground control points i also used a program called ground gcp editor pro and it's about a 50 program but i bought it uh when i bought like a user guide for open drone map and they give give me a discount i think i might have paid 39 or something for it but it does allow you to do the the tagging of the various points of interest that you have in a set of images like say you have a point and then you you're using a matrix like three by three matrix of photos that are right around that point and using them to uh to identify where that point is in each one of the photos if you've done any any of that type of work before with pix4d or any of that it's very very similar to what you would do with that this is just a one-time purchase deal where where you're able to do a similar thing to generate the ground the gcp list dot text which is the the list of references to those points in images that allow you to geo-reference a an image so the next part i want to show you is from that same area one that has been modified with the fake ground control points and i'm going to take the opacity down to 50 on this one and you see where it's virtually spot on and i'll take you to a couple other points of interest that i used as ground control points this is a sewer manhole cover a stand pipe that is quite a bit up above the ground but i'll take that down and you see how it's lining up where the in the other image will flip back to the non gcp file and now you can see where the manhole is way down here so the end result of this the simplified message that i want to give you is that using ground control points that aren't necessarily the the perfect uh surveyed using gps equipment and and sub meter uh accuracy or sub centimeter accuracy that you can get out of some units you can still end up with a very good product at the end of it if you're not doing deliverables for something like a surveyor to have them use it in their their work or to do cut and fills that a contractor might be getting paid for i wouldn't use it for any any of those kind of things but to try to get a map to line up between what you shot with your drone and something like open street maps or bing or google if you're overlaying those images similar to what you're seeing on the screen right now if you're overlaying those images to try to get them to match up without having to do an awful lot of photoshop work so that's it for this video the next video i'll go into the details of how i created that but i just want you to get the message that you can do some very good referencing even without gps equipment out there to get things to line up properly with other other services so that's it thanks for watching bye

Channel: Mike Williamson

Views: 634

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Id: h6E4ooMvL1c

Length: 5min 35sec (335 seconds)

Published: Thu Sep 17 2020