Emlid Caster VS Local NTRIP

[jmason702]

I use Emlid Caster to send corrections to the drone (caster.emlid.com as the IP address), Never have used Local NTRIP to send corrections.

Bottom line, which is better and why, please? and or the benefits of both and vis versa

Thanks

 

[Dave Pitman]

Bottom line, which is better and why, please?

So long as your internet connections are stable throughout the entire mission, there is no difference.
Using Emlid Caster, any interruption in cellular data can cause a loss of precision.
Using Local Caster, there is no cellular data in the chain, so no chance of possible interruption from loss of cellular.

With Emlid caster, the RS is sending corrections to the Emlid server and the server is sending the correction back to the rover.
With Local caster, the RS is sending corrections directly to the rover.

 

[jmason702]

Another question I have, with RTK drones, is whether it is better to set your GCPs in WGS84 (Global CS)
or in your state plane? I did a mission the other day for practice, using the state plane on my points, and my data is off.
When I keep the data the same as the drone, in WGS84. My workflow seems smoother and can export it out in state plane.
This is only with RTK drones. Thoughts on this?

 

[jmason702]

when using Local NTRIP can you send corrections to the drone and a rover such as RS+ at the same time?

 

[Dave Pitman]

Another question I have, with RTK drones, is whether it is better to set your GCPs in WGS84 (Global CS)
or in your state plane? I did a mission the other day for practice, using the state plane on my points, and my data is off.
When I keep the data the same as the drone, in WGS84. My workflow seems smoother and can export it out in state plane.
This is only with RTK drones. Thoughts on this?

The drone uses wgs84. There is no way to set it to use anything else. So, if your ground control is also in wgs84, you are good to go.
If you are using NTRIP to set your base point, and the NTRIP is referencing NAD83, then when you process your image set, you will need to get the images to match the base point CRS, NAD83 in this example.
In Metashape you do this by importing the images. MS will correctly determine wgs84 from the exif.
Then convert the images CRS to NAD83.
Followed by importing the ground control which you specify as using NAD83.

You could optionally convert all of your collected ground points to wgs.84 beforehand.

 

[Dave Pitman]

when using Local NTRIP can you send corrections to the drone and a rover such as RS+ at the same time?

Local is not practical for terrestrial rovers because they will be out of range of your hotspot. Either LoRa, Emlid Caster, or Network NTRIP for those. If you have no cell service, then LoRa only.

Emlid built Local Caster for drone ops because the drone controller can remain near the RS within the one hot spot network.

 

[jaja6009]

The drone uses wgs84. There is no way to set it to use anything else. So, if your ground control is also in wgs84, you are good to go.
If you are using NTRIP to set your base point, and the NTRIP is referencing NAD83, then when you process your image set, you will need to get the images to match the base point CRS, NAD83 in this example.
In Metashape you do this by importing the images. MS will correctly determine wgs84 from the exif.
Then convert the images CRS to NAD83.
Followed by importing the ground control which you specify as using NAD83.

You could optionally convert all of your collected ground points to wgs.84 beforehand.

This is what I do.

I setup my RS2 Base on a high quality NAD83(2011) NGS survey monument. It was used with helping to constrain Geoid 18 and is a quality point in my opinion. It actually pulls the orthometric height up as compared to the new GRAV-D data. (I cannot wait for the confusion when the new Vertical Datum comes out and people think our area sunk).
Now my Base is outputting NAD 83(2011) in NTRIP on Emlid Caster.

I use my RS+ to lay any control points using the setting GCS and ellipsoid and am receiving my corrections over NTRIP in NAD83(2011) ellipsoid since my Base is outputting this GCS and ellipsoid heights.

I connect my Phantom 4 RTK controller to a hot spot and now receive corrections in NAD83(2011) ellipsoid heights.

In Agisoft it asks three things.

Output Coordinate System - I use NAD83(2011) New Jersey State Plane with NAVD88 using Geoid 18 or NAD83(2011) UTM 18N with NAVD88 (Geoid 18) (I had to manually download Geoid 18 from Metashape and assign it to NAVD88)
Images System - I tell it NAD 83 (2011) with ellipsoid heights since that is what my Base was putting out over NTRIP
Control Points System - I tell it NAD 83(2011) with ellipsoid heights since that is what my Base was putting out over NTRIP

This workflow has worked well for me and allows me to easily use Geoid 12 if that is what is asked for.

I do not do any type of conversion, I just tell Metashape in the Reference Settings that my images and Control Points are in NAD 83 (2011) ellipsoid heights since that is what corrections the RS+ Rover and P4RTK were receiving.

 

[jmason702]

use my RS+ to lay any control points using the setting GCS and ellipsoid and am receiving my corrections over NTRIP in NAD83(2011) ellipsoid since my Base is outputting this GCS and ellipsoid heights.

when I survey a point in NAV 88 it gives me the geoid elevation

 

[jmason702]

Let me send you this file set, and if you could please screen shot your settings in meta shape

 

[jmason702]

HOME TEST - Google Drive

drive.google.com

 

[jmason702]

Here is a data set with 4 points in state plane, If anyone feels like looking and putting through your workflow and sharing how you do it in meta shape, please do, cause Im getting numbers that are way off for some reason
RS2 sat for 20 min in NTRIP collecting its point, and points were pulled over Lora radio as FIX with RS+

 

[jmason702]

new link

HOME TEST - Google Drive

drive.google.com

 

[jmason702]

should be 265 files with points

 

[Dave Pitman]

How you liking the M3E ?

 

[jaja6009]

I ran your data in Metashape.



I used Gradual Selection in three phases similar to USGS's workflow and optimized after each phase, with the final optimization being all parameters and Fit Additional corrections.


I am really digging your Mavic 3E datasets. I am so tempted to grab one, but my Phantom 4 RTK has yet to dissappoint me.

First thing you might need to do is download Geoid 18 from Agisoft.

For this dataset,


Above is the Main Reference Panel






Above this is the settings for the Custom Projected Nevada State Plane you will have to make and use.
You will also have to assign Geoid 18 to be your NAVD88 Geoid of choice.


The Coordinate System (Output) - use the Custom Nevada State Plane ft US, make sure you have downloaded and installed Geoid 18 from Agisoft and make sure you use ftUS and not meters. Use NAVD88 ft

Camera Reference - Use NAD83(2011) the Geographic Coordinate System as from all of your other datasets you seem to be using a RTN NTRIP service that outputs NAD83(2011)

Marker Reference - Use the same Custom Nevade State Plane ft US

 

[jmason702]

WOW, Thanks Bro, Much effort and time I really appreciate it!
6521 was always my go-to EPSG code has something changed? and should I set up my gear in 6318 as you have on here?
I downloaded the Geoid 18, but it is a tiff file and I can't get it to install on meta shape. I went on their web page and found downloads for Geoids can you walk me through that a lil bit?

 

[jmason702]

How you liking the M3E ?

I like it!
Pros- It's a mapping BEAST, as in speed and flight control, it is very fast and accurate!
Cons- Geo-Fencing, and I like the Orthos from the EVO RTK better, to me they look better, and the edges and corners of the building, etc... seem to be better.

In Vegas 65% of our area is class B space. So I will be using both drones quite a bit. As far as accuracy from both of them from my findings I would say equal...

 

[jmason702]

I just checked on Emlid App and codes 6318 and 8228 are not in there, so I assume I stay in the same 6521 when pulling my points and NAV88ftUS

 

[jmason702]

I have the Free trial of meta shape, mabey why it is not loading into the system, But what I am is confused. I had all this down really well.
And now I feel I don't know what is going on, was there some change in the systems in the states?
Not sure, but I need to figure this out.
Also, my DD account is almost up and I am so torn on what to get, keep DD, or move on to meta shape or Sim Active, or something else.
I need to produce non-radio metic maps as well, so Sim Active is kinda out. Meta shape is getting more confusing. and DD works great with RTK until you add GCPs or Check into the mix. Just venting my thought here... Thanks

 

[jaja6009]

I think your problem (guess) is that you were using 6521 (State Plane Projected Coordinate System) along with NAVD88 using meters instead of us ft in Agisoft. And if you were using Geoid 12 that most likely differed too.

You use Drone Deploy, so I see why you want and need your elevations in orthometric instead of ellipsoid. I only use Drone Deploy for a project I want to mass share or to test something. I actually find Drone Deploy harder to use than Agisoft. Agisoft for me is so easy. Tell it what you want to output in, tell it what your drone images are in and tell it what your markers are in. It does the rest and is so flexible. For this reason I chose it over Pix4D mapper. Pix4D matic though does have local geoid support and undulation grids (The geoidal height so that you can use H=h-N on each drone image coordinates).


On code 6318 in Emlid. Just use the default GCS setting. NAD83(2011) (6318) is a global coordinate system just like WGS84. If you lay them over top of each other they match (for our intents and purposes). They only differ in where they think the center of the earth is at the current time and have a shift. With a Rover receiving corrections, it receives whatever GCS is sent to it by the Base. Example: You are receving RTN NTRIP in NAD 83 2011, your RS2 is now in NAD83 2011. You averaged a point with your RS2 from your NTRIP and are now sending corrections to your drone, your RS2 is sending NAD83 2011 and your drone is receiving NAD 83 2011.

Here is a link for adding Geoid 18: How to use height above geoid for the coordinate system

You could do this:

1. Obtain your known point - Receive NTRIP and average on your RS2. You now have a known point in NAD83 (2011) with ellipsoid elevations.
2. Setup your RS2 as your base now. Enter the averaged coordinates and ellipsoid height in Manual. You can now output NAD 83 (2011) with ellipsoid heights over Emlid Caster and your drone will now receive that.
3. Get your RS+ setup as your Rover. Use the default GCS setting and ellipsoid heights. Your RS+ is now receiving NAD83 (2011) and ellipsoid height.
4. Gather your Control Points.
5. Fly your mission.

You now have: drone images in NAD83 (2011) and ellipsoid heights and Control Points in NAD83(2011) with ellipsoid heights
This data works great in Agisoft, but you will need orthometric heights for Drone Deploy unless you use GCPs.

Load the images into Agisoft and export from the Reference Pane into a csv.
Visit NGS Geoid 18 Computational Tool and use the multiple files tool on the bottom. This tool needs just the coordinates in the desired format (see the instructions).
It will produce a list of the geoid undulation or geoidal height for each coordinate given.
copy and paste this into the original csv in a new column. Make a new column where you will make an orthometric height column. Use H=h-N or Orthometric Height = ellipsoid height - geoid undulation (what you received from the Geoid 18 Tool).
That new colum now has orthometric heights.

Use a metadata editing tool and change all of your images altitudes to the new orthometric heights. Upload to Drone Deploy.