Poor mans GCP?

Good morning,
I am flying a mavic pro. I have used Dronedeploy for about a year. My question is there a poor mans work around for GCP’s? I am manually flying the same yard at the same height for a landscaping project to capture growth and shad tracks, along with planning ans elevation changes. I has been working ok but it is off by several feet when I do the “compare”. A quick look online and in forum’s and it looks like it is pretty expensive to do GCP’s for the average guy. for time to time.

  1. What is the most inexpensive way to do GCP’s?
  2. I have stumps and rocks that never move and I all ways fly the yard at 40ft. Is there a way to at least get the maps to always use those reference points so it is more repeatable?

Thanks
Tim

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You’re in luck. @MichaelL posted a great way to have all your maps align.

Thanks, I have downloaded QGIS now, but have never used it. is there a basic video on how to DD maps? The linked video seems to assume that you already know how…

Thanks
Tim

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In QGIS, you can just drag the geo.tiff in and QGIS will place it on it’s own layer. Then, you right-click on the .tiff and “SET CRS” and make sure that it’s on WGS 84. Then just follow along with the video. No experience needed. Ask if you get hung up on something.

Thanks, so I was able to get one in… baby steps. So The file that uploaded was the ortho from June 1. Under that "Project " I have several dates of orthos that I click through to see the yard over time. How do I export othe dates in that project. I scroll through to the ortho I want and export, but it only sends the June 1 ortho for the project.
Oh and witch WGS 84? there are several, or does it not matter witch?
Thanks,
And if there is a video or something I will stop buggin the forum with this low level stuff… :grin:

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Sorry Tim, I don’t currently process with Drone Deploy so can’t help with getting other dates out. I suspect it shouldn’t be difficult and one of the other guys (@MichaelL) will chime in if you don’t figure it out.

I don’t know that it matters which version of WGS 84. An easy way to go is open a clean copy of QGIS.
Go to “Settings > Options > CRS” and select the top option “use CRS from first layer added” and let QGIS assign the correct system based upon your geotiff when you add it.

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Hey Tim. The exports apply to whichever map is in view. If you toggle left or right to go to the different dates then that is what will be exported. The idea behind creating control points in this manner would be to do it after the first map so that all future maps are relative to it, but it can be done at any point in time and re-processed backwards or forwards.

EPSG 4326 is the latest revision of WGS84, but you can use whatever CRS you want just as long as it matches what you exported. You might consider exporting it out in your State Plane coordinate system as well.

Tim: When setting GCPs, it’s good to use the best GPS equipment you have available. For a good, inexpensive GPS unit, check out the BadElf. You can even post process the results if you need/want to do that; but out of the box, it’s sub-meter accurate.
If you’re getting the doming/dishing (elevation) error in your ground model, you can improve the results (even without GCPs) by using curved, convergent, non-traditional (non-linear/non-parallel) flight lines to a) provide a more diverse view perspective and b) help mitigate the SfM doming/dishing (elevation) error. Throw in a few slightly oblique (5 to 10 degrees off nadir) photos; and that will help as well.
I’ve attached an example of the curved flight lines to show you what I’m talking about.

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Bad Elf products are barely better than a cell phone with an averaging app. My thread on rough gcps are as accurate as that data. You really need to be looking for something that can log data and be corrected if desired.

Michael, thanks for the video. It was very helpful and I was able to follow it step by step. I did use google sheets instead of excel. So next dumb question how do i import it back into drone deploy? At the end of the video you mention it but I have never done it. Also am I importing the CSV ? Lastly I have flown the sight about 5 times over the past 8 months. How do I get them all to line up now that I have done this process?
Sorry for all the questions, just trying to figure it all out.
Thanks
Tim

I’m happy I could help. You will need to manually re-upload any maps that you want aligned. Moving forward this is why I do it immediately on the first map, but as long as you have the bandwidth 3 uploading shouldn’t be too bad. It should be well worth the effort.

Thank you so much for the help, there is not a lot of information out there that is specific to this, and I am new to both Dronedeploy (less than 20 maps) and QGIS.
So when you say manually re-upload do you mean into QGIS or Dronedeploy? In short I have fly this project about 5 times over the past 8 months. During that time tree cover has changed both seasonally and because of tree removal. Also because of the sight the same flight is not done every time. I try to make the height as regular as possible now as I’m learning . The larger map was flown by the DD app at 180 ft (November 2019) and the smaller inset was under the tree canopy at about 40 manually, last week. I made the GCP shape file using the smaller map and a mix of hard points and Amazon GCP markers.
To try ti figure this out I have attached a screen shot. I would like to be able to have all the maps line up, as you can see in the screen shot they are off by about 5 to 8 ft.
Thanks!
Tim

It’s not surprising there isn’t much information because noone that I have seen or heard is doing anything like this. Most people are using GCP’s for ultimate accuracy and the fact is that there are allot of cases that people just want decent accuracy and all the maps in the series to align. With processing of images only with native drone GPS you will see image adjustments up to 12-15ft and they are relative only to that flight. The machine tries to fix it as best as it can, but that is just the limitation. Pulling information from Google Earth is another step that you can take up front to create GCP’s before you ever fly if there are enough permanent objects on the ground to locate. It will get you within 2m (6ft) easy and depending on the update of the Google Map you can get down to 1m (3ft) on the RMSE.

Here is the other similar thread.

…and some support docs.

Uploading Manually

Processing GCP’s