Increasing Vertical Accuracy

My question is: what is currently the best method to increase the vertical accuracy of DEMs generated by MME?

I submitted a "Georeferenced w/Manual GCPs" job to MME. I included 7 GCP points, 4 of them being anchor points identified on two photos. The GCPs were surveyed using RTK GPS and the coordinates are accurate within about 1" but due to the resolution of the photos could probably only be identified to about 4".

When I got the products from MME I compared the DEM elevations at the GCP targets to the RTK GPS coordinates. I expected them to be very accurate at the points where the GCPs were defined, and somewhat less accurate between GCPs. What I found what differences ranging from +1ft to -4ft. Horizontal accuracies at the same points are sub-foot.

As the intention is for the DEM to be used for volume calculations I would like to improve the vertical accuracy of the MME DEM so it more closely matches elevations provided by GPS.

I have reviewed Neil's post and Mark Heil's response regarding the use of ArcGIS 3D Analyst from the start of 2017. Interested to know if there are any newer methods or if this is still the best approach to improve the vertical accuracy of my MME generated DEM?

Dugald Dunlop 7 September, 2017 19:15

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The current version of the Manual GCP process is not intended for users that have geotagged images. it was designed to be used with cameras that don't have GPS information embedded in their tags.

The best way to process imagery using accurate GPS data is to use the normal geotag image based workflow and then use QGIS to accurately adjust the Maps Made Easy output to use your GCP data.

https://support.dronesmadeeasy.com/hc/en-us/articles/115003655066-Georeferencing-Aerial-Maps

The Maps Made Easy outputs are very accurate relative to themselves can be up to a few meters off of real world measurements due to the GPS accuracy of the aircraft.

Zane 8 September, 2017 17:20 0 suara

Sorry but I'm having a hard time understanding this. Most aerial mapping software use gcp's to allow correction of the outputs to a much more precise level than the gps tags. You seem to be saying not to use gcp's but use the gps tags then use another program (QGIS) to use the gcp's?

Dlbeck11 5 November, 2017 05:34 0 suara

We do not use our GCPs to stretch the generated model so it is just enough to get it reasonably close for users that couldn't previously reference it easily. If you really care about the points lining up super well you need to use something that will warp the input files to make the points match. GIS software is a good way to do this. We may offer a way of doing this directly within Maps Made Easy in the future but it would be done after using the normal geotagged workflow like we are recommending.

Zane 6 November, 2017 17:16 0 suara