Base Stations

[BBUAV]

Hello, I recently purchased the M4E and have had pretty good results with RTK with an NTRIP service. I want to utilize GCPs and a base station for better accuracy and for areas I may not have NTRIP signal. I have been looking at Propeller Aeropoints vs DJI RTK3 vs Emlid RS3.
The Aeropoints look like a great option and a lot faster for data collecting but seem they may be more costly in the long run.
Propeller has not returned my emails or calls so I'm leaning towards one of the other two. Any thoughts on going with one over the other in your experiences? Im not sure if the DJI RTK3 would work with other drone brands so thats why Im also considering the RS3 for the money.

 

[jaja6009]

Aeropoints work great, they are just expensive and can be a nightmare for security since they are so expensive.
Keep in mind that if you have a large site, you may run out of aeropoints, where if you were using traditional control points with a GNSS rover you would not.

I use an Emlid RS3 and it works for my use cases well.
In terms of being in an area with no internet, you would need 2 Emlid units. One as a base and one as a rover. In an area with no internet, the single DRTK 3 would not work to collect control points.

A simple workflow with 2 Emlid units in an internet denied area.

Known Point: Make your own in the days previous to your flight using PPK or OPUS (Setup Base unit and log for 24 hours) then process in NGS OPUS or Emlid Studio PPK software.

Day of flight: Setup Emlid Base on your new known point. layout and collect your control points using the second Emlid unit. You can receive corrections using the Lora Radio (Works great for line out sight distances.) Send corrections to your drone using Local NTRIP (You and the controller will need to be within 50 feet or so of the base due to this being a Wifi connection between the Emlid unit and your controller).

Process your data, but make sure you collected enough control points to serve as both GCPs (Ground Control Points) and Check Points (To check your accuracy). A lot of new mappers don't seem to realize that they need Check Points to check the maps/ accuracy and precision.

ABove is assuming you need absolute accuracy (placement in the real world ie. the corner of the building is at the correct coordinates as in the real world.). If you only need Relative accuracy, then you can just setup your base anywhere and do the above process.

 

[BBUAV]

Aeropoints work great, they are just expensive and can be a nightmare for security since they are so expensive.
Keep in mind that if you have a large site, you may run out of aeropoints, where if you were using traditional control points with a GNSS rover you would not.

I use an Emlid RS3 and it works for my use cases well.
In terms of being in an area with no internet, you would need 2 Emlid units. One as a base and one as a rover. In an area with no internet, the single DRTK 3 would not work to collect control points.

A simple workflow with 2 Emlid units in an internet denied area.

Known Point: Make your own in the days previous to your flight using PPK or OPUS (Setup Base unit and log for 24 hours) then process in NGS OPUS or Emlid Studio PPK software.

Day of flight: Setup Emlid Base on your new known point. layout and collect your control points using the second Emlid unit. You can receive corrections using the Lora Radio (Works great for line out sight distances.) Send corrections to your drone using Local NTRIP (You and the controller will need to be within 50 feet or so of the base due to this being a Wifi connection between the Emlid unit and your controller).

Process your data, but make sure you collected enough control points to serve as both GCPs (Ground Control Points) and Check Points (To check your accuracy). A lot of new mappers don't seem to realize that they need Check Points to check the maps/ accuracy and precision.

ABove is assuming you need absolute accuracy (placement in the real world ie. the corner of the building is at the correct coordinates as in the real world.). If you only need Relative accuracy, then you can just setup your base anywhere and do the above process.

Thanks for the response. I didnt think about needing a second unit when not having internet. I was thinking about the ground station as base and the drone as rover. I will make sure I get back to the drawing board on how those work together.

I have been following several of your posts on the M4E and mapping and have learned a lot from you already.
Thank you sir for taking the time to post and answer questions.

 

[jaja6009]

Thanks for the response. I didnt think about needing a second unit when not having internet. I was thinking about the ground station as base and the drone as rover. I will make sure I get back to the drawing board on how those work together.

I have been following several of your posts on the M4E and mapping and have learned a lot from you already.
Thank you sir for taking the time to post and answer questions.

Having two is the best way to do this. You can do it with one.

An example is if you are in an area with close NGS CORS stations, then you could collect your control points using PPK. To collect points you just setup on the point and record for 2 minutes. Then fly your flight using Local NTRIP with an Emlid unit, or the seamless connection using DRTK 3.

In the office you download the logs from a CORS station (free as long as it was an NGS CORS). Use the logs from the EMlid unit or DRTK 3 to post process to get your new corrected positions on the control points and then use either Terra or Emlid Studio (Or I prefer Red Tool Box) to correct yourt image's coordinates.

There are way too many ways to do this for me to type out. But I usually tell people the easiest way, although the easiest way usually has a cost.

Do not be scared of PPK as it is usually the most accurate way to do this, and once learned is pretty straightforward.

 

[BBUAV]

Having two is the best way to do this. You can do it with one.

An example is if you are in an area with close NGS CORS stations, then you could collect your control points using PPK. To collect points you just setup on the point and record for 2 minutes. Then fly your flight using Local NTRIP with an Emlid unit, or the seamless connection using DRTK 3.

In the office you download the logs from a CORS station (free as long as it was an NGS CORS). Use the logs from the EMlid unit or DRTK 3 to post process to get your new corrected positions on the control points and then use either Terra or Emlid Studio (Or I prefer Red Tool Box) to correct yourt image's coordinates.

There are way too many ways to do this for me to type out. But I usually tell people the easiest way, although the easiest way usually has a cost.

Do not be scared of PPK as it is usually the most accurate way to do this, and once learned is pretty straightforward.

Good to know. It is definitely a lot to take in when first learning, I'm still trying to wrap my head around the different ways to offer deliverables let alone the different ways of collecting accurate data. Its been a lot to invest in so I may pull the trigger on one RS3 so I can get the hang of PPK processing.

 

[jaja6009]

Good to know. It is definitely a lot to take in when first learning, I'm still trying to wrap my head around the different ways to offer deliverables let alone the different ways of collecting accurate data. Its been a lot to invest in so I may pull the trigger on one RS3 so I can get the hang of PPK processing.

NGS CORS map. Shows you where the stations are located. I like for them to be less than 50 km for PPK.

ArcGIS Web Application

www.arcgis.com

But you can do something like this with one GNSS unit.

Get on site, immediately place your Emlid and start logging. Get a good 10, 15 minutes.

Collect your control points by sitting on them for 2 minutes each.

Fly your mission using Local NTRIP.

In the office run PPK for your base position. Then use this base position to PPK your drone images off of the base since it is on site and much closer most likely than an NGS CORS.


Also check if your state has free RTK corrections. Some do.

 

[BBUAV]

I haved looked into the CORS network in my area and its seems pretty cumbersome for the northern nevada area. I have been using a trial for a paid service and it seems to work pretty good and has pretty good coverage in rural NV I would be working.
On this Quality Report I have been looking at the RMS Errors as well as Absolute Accuracy columns to determine a decent accuracy of the NTRIP. Is that a correct assumption or should I be reading the report differently?

 

[jaja6009]

I haved looked into the CORS network in my area and its seems pretty cumbersome for the northern nevada area. I have been using a trial for a paid service and it seems to work pretty good and has pretty good coverage in rural NV I would be working.
On this Quality Report I have been looking at the RMS Errors as well as Absolute Accuracy columns to determine a decent accuracy of the NTRIP. Is that a correct assumption or should I be reading the report differently?

View attachment 31092

If you want to assess the accuracy/precision of your outputs (maps, DEMs etc.), you have to have Check Points. Then look at the RMSE of the Check Points. The RMS error of GCPs is more about how well you marked them.
Make sure your Check Points are well spread in your mapped area, sort of like placing legs under a table with a flimsy tabletop to support it.

 

[BBUAV]

Got it! Thank you sir