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Altitude not corrected after adding GCPs

Hello,

On the latest map : EJD EBOULEMENTS

The altitude was not corrected. Is it possible to have a look at this problem please ?

Thank you.

Martin Richard

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I am seeing that for point 4 the GCP elevation value was 419. This appears to be close to the value in the DEM. It was 429 or so in the original.

Point 7's elevation value was 399 in your GCP file which appears to be reflected in the adjusted version. I was 408 or so previously.

Keep in mind that the only non-linear adjustments occur in the X and Y directions. The vertical shape of your model is not adjusted based on your GCP inputs. Only a linear adjustment/offset is applied. The error is minimized for all GCPs so the individual values may not be right on.

Basically your model isn't going to get any more accurate in a relative sense using this process. If your model is bad to start with it isn't going to be accurate everywhere. 

You had pretty minimal overlap in certain sections which does not help the model's accuracy. If you are going to care about the accuracy of the elevation numbers your entire Overlap Report needs to be in the dark blue zone which corresponds to using 80/80 overlap and taking off from the highest point you are going to be covering.

Zane
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I'm running into the same issues with a quarry (maybe 2) that I had flown a few weeks ago before the snow came. I recorded GCP's with RTK GPS (0.01 accuracy)  I'm seeing an average diff in elevation of -4.76 m btwn my GCP's and MME elev.

When I compare the diff in Z from corner to corner of site (highest to lowest point) I'm finding an error of 1.5 m btwn my GCP's and MME elevations. (likely from poor overlap as I have discovered in this and other posts) but on avg only a diff of 0.15m which i can live with.

Is there a way to adjust the elevations after processing to match my GCP elevations? or at least a little closer.

I'm using P4 pro V2

Jamie Flewelling 0 votes
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Jamie: The overlap feedback applies to you as well. A lot of your model was in the greens and yellows which isn't going to help your initial model accuracy.  

You probably have too many GCPs too... 

Use at least 80/80 overlap to get your model right. Then use 5-10 GCPs, not 35. 

Zane 0 votes
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Hi Jamie,

The job was approximatly 700 meters X 350 meters. I done the job a second time with 75X75 overlap at 90 meters alt. with 17 GCP's and everything is OK now.

 

Hope it helps, have a nice day.

Martin Richard 0 votes
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