Autel Evo 3 RTK State plain question

[Manny58200]

Everyone

I am having an issue. My field surveyor is working on the boarder of New Hampshire and Massachusetts. Our project is in New Hampshire and is NAD83 New Hampshire (FTUS) and NAVD88 (FTUS). He connected our Autel Evo 3 RTK to the Masscores Network (because it was closer than anything in NH) and preformed a drone topo of the site. He told me the drone does not give him the option to pick which state plain he is working in. I processed the flight in Pix4Dmatic and Pix4dmapper. When I process it in Matic I use NAD83 New Hampshire (FTUS) and NAVD88 (FTUS) and Geoid 18. At the end of the process I get a large RMS error of .45ft. The surface is between .1ft -1ft off my random grid check.

Questions
1 Does Autel give you the ability to pick your Horizontal and vertical datum when connecting to a RTK Network?
2 If no above what does it use and how does that relate to a Geoid?
3 Does RTK Reference station send the information in their respective state plain or is it a static position?
4 If static position above how does that relate to processing?

Thanks in advance to anyone taking the time to help me.

 

[camazu]

I use an Autel Evo II with an Emlid Reach RS2 and from what I understand all the data is processed in WGS 84 at the drone level. Therefore, I use GCP in state plane coordinates for my processing in DroneDeploy.

 

[jaja6009]

Your drone receives corrections in the same datum/coordinate system that you are receiving in. So if you are connected to Masscores and its is giving corrections in NAD83(2011) with ellipsoidal elevations (My Guess), then your drone is receiving corrections in NAD83(2011) with ellipsod elevations. You need to ask Masscore what datum/coordinate system they are using.

Your questions
1. No, Autel and DJI do not give you the ability to pick the datum, but again, the datum will be whatever you are receiving corrections in. If not using RTK, it would then be WGS84. But it doesn't matter because without RTK the values received are not accurate enough to discern the difference between WGS84 and NAD83(2011). But with corrections being received you are now accurate enough to discern the 1 to 2 meter shift between WGS84 and NAD83(2011).
2. This question relates to question 1. GNSS hardware natively receives corrections in a geographic datum and uses an ellipsoid for elevations. Software or yourself can apply the geoid to the ellipsoid elevations using H=h-N.
3. I cannot speak for all RTK RTN services, but the ones I have used send corrections in a geographic system. Terrestrial GNSS usually has software that can transform to State Planes, UTM etc. and also give orthometric elevations. I am unsure on the rest of your question. The RTK reference station will send you corrections for your position using its known position.
4. See above.

Here are some problems and solutions.

1. Did you take all nadir images (looking straight down)? If so this will introduce a vertical shift. Use the Altitude Optimization setting in the future so it can add one line of oblique images from the outside corner of the project area to the center. This vertical shift is well known and will happen regardless of the photogrammetry software you use.

2. Confirm the datum being used by Masscores. I would bet money on it being NAD83(2011) using an ellipsoid elevation.

3. In Pix4Dmapper use the following settings. Assuming that Masscore is sending corrections in NAD83(2011) with ellipsoid elevations.

Images - NAD83(2011) - Vertical Height Above GRS80 Ellipsoid - This is because your images are using an ellipsoid elevation. Make sure you choose the geographic system with the globe icon and in meters.
Output - NAD83(2011) New Hamp State Plane , Vertical Height Above GRS 80 Ellipsoid. Place the geoid undulation in this field. You can obtain it from below.

Click in the center point of the area mapped, get the coordinates (In NAD83(2011), not State Plane. Take those coordinates and plug them into this official NGS Geoid 18 Tool: GEOID18 Interactive Computation | GEOID | Data & Imagery | National Geodetic Survey
This is the geoid undulation for your project area. The undulation is the difference in height between the geoid and the ellipsoid in that area.
Now for the Vertical system in the Height Above GRS80 ellipsoid, place the geoid undulation obtained from the tool.
Your ouput will now be in NAVD88 using Geoid 18.




In Pix4D Matic

Change the Image Datum/Coordinate system to NAD83(2011) with Vertical being Ellipsoid Elevation GRS80
Change the Output/Tie Point Coordinate System to NAD83(2011) New Hamp State Plane USft and Vertical to NAVD88 and Geoid to Geoid 18.

 

[jaja6009]

I use an Autel Evo II with an Emlid Reach RS2 and from what I understand all the data is processed in WGS 84 at the drone level. Therefore, I use GCP in state plane coordinates for my processing in DroneDeploy.

When using the consumer GPS/GNSS chip, yes the drone will use WGS84.

When using the RTK module, your images will be tagged using the datum/coordinate system that the base is sending corrections in.
So if using Point One, it would be the newest realization of WGS84 since that is what Point One sends corrections in.
For my RTK network, they send in NAD83(2011) with ellipsoid elevations, so that is what my images will be in.
If I setup an Emlid on an NGS monument and this monument is in NAD83(2011) with ellipsoid elevations, than my drone or terrestrial rover would be receiving corrections in NAD83(2011) with ellipsoid elevations. A thing to note for the OP, Emlid can allow the Rover to receive corrections in a projected system using software in Emlid Flow.