Mavic 3E RTK Question?

[MikeTX]

So I have experience in mapping from work where I fly the M300 utilizing the P1 35mm camera. For RTK we use the Pix4D viDoc and input everything either into Mapper or Matic.

I now have a Mavic 3E for personal use to do things on the side, with the RTK Module incoming.

My question is how well does the Mavic 3E do utilize the RTK module attachment? How good is it for accuracy? I'm clearly not getting into surveying at the moment so I would just need it to be semi decent.

 

[jaja6009]

The Mavic 3E (M3E) is an excellent mapping drone.
With the RTK module and using NTRIP you can obtain low centimeter accuracy/precision without any GCPs as long as you don't just use nadir images. The M3E also has a mechanical shutter so you can move very quickly while taking your images and not have any motion blur. Finally the M3E can write images much faster than previous DJI mapping drones such as the Phantom 4 RTK.

You will be very happy with the M3E if you like the M300 RTK with P1.

 

[herbertlincon]

So I have experience in mapping from work where I fly the M300 utilizing the P1 35mm camera. For RTK we use the Pix4D viDoc and input everything either into Mapper or Matic.

I now have a Mavic 3E for personal use to do things on the side, with the RTK Module incoming.

My question is how well does the Mavic 3E do utilize the RTK module attachment? How good is it for accuracy? I'm clearly not getting into surveying at the moment so I would just need it to be semi decent.

You can use the RTK module together with a D-RTK 2 base station, having a centimeter precision.

 

[kinetix]

I have done some mapping with a P4Pv2.0 and am now considering the Mavic3E RTK to do construction and other mapping. Besides the drone, I assume I need a base station of some kind. Is there a resource I can go to to learn what equipment is needed and how to proceed?

 

[kinetix]

The Mavic 3E (M3E) is an excellent mapping drone.
With the RTK module and using NTRIP you can obtain low centimeter accuracy/precision without any GCPs as long as you don't just use nadir images. The M3E also has a mechanical shutter so you can move very quickly while taking your images and not have any motion blur. Finally the M3E can write images much faster than previous DJI mapping drones such as the Phantom 4 RTK.

You will be very happy with the M3E if you like the M300 RTK with P1.

jaja6009, I've done some mapping with DD and a P4P on the side of my construction management job. I'm going into drone work full-time and looking at the M3E. What do I need to have or do to get the cm level accuracy that is being talked about?​

thanks,

Doug

 

[jaja6009]

You will need to receive corrections from:

1. DRTK 1 or 2, Emlid GNSS Receiver - both on a known point. (Your accuracy will be as accurate as your known point. An NGS monument or surveyed point can also work well.

2. A corrections service such as Trimble, or similar.

3. An understanding of datums and coordinate systems, both horizontal and vertical.

4. Control Points - Used as either a GCP to introduce the accuracy and Check Points to check the accuracy. GCPs are optional with the RTK on the M3E, but I still use at least one for important projects.

 

[kinetix]

You will need to receive corrections from:

1. DRTK 1 or 2, Emlid GNSS Receiver - both on a known point. (Your accuracy will be as accurate as your known point. An NGS monument or surveyed point can also work well.

2. A corrections service such as Trimble, or similar.

3. An understanding of datums and coordinate systems, both horizontal and vertical.

4. Control Points - Used as either a GCP to introduce the accuracy and Check Points to check the accuracy. GCPs are optional with the RTK on the M3E, but I still use at least one for important projects.

Thanks for your reply. Can you point me to a resource to help me learn more about these options?

 

[rfb]

You will need to receive corrections from:

1. DRTK 1 or 2, Emlid GNSS Receiver - both on a known point. (Your accuracy will be as accurate as your known point. An NGS monument or surveyed point can also work well.

2. A corrections service such as Trimble, or similar.

3. An understanding of datums and coordinate systems, both horizontal and vertical.

4. Control Points - Used as either a GCP to introduce the accuracy and Check Points to check the accuracy. GCPs are optional with the RTK on the M3E, but I still use at least one for important projects.

Thank you for the information. How accurate would my data be if I use the DRTK-2 on an unknown location? Would it still be significantly low?

Thank you for your time.

 

[Dogpilot]

The accuracy is lower with the D-RTK-2 at any random location close to where you are working. Exactly how much depends on a whole lot of factors. If you place it on a known control point, it gets a lot better, down to 5 cm I believe. There are a lot of known control points, check out this listing. There tend to be ones nearby to most spots. The D-RTK-2 will only transmit line of sight about 8 km, perhaps a bit more. the accuracy decrease per Km, I think the rate of accuracy loss is on the specs page. You will also need to go to a lat/lon conversion page (lots of them) to change the coordinate system to the Lat.000 spec the D-RTK-2 wants to see. You also need to correct the datum height from the map listing of the control point to account for the pole the RTK is mounted on.

NGS Map

 

[jaja6009]

Thank you for the information. How accurate would my data be if I use the DRTK-2 on an unknown location? Would it still be significantly low?

Thank you for your time.

Yes, if you just use the DRTK to obtain its coordinates while not receiving corrections or being placed on a known point, your absolute accuracy will be bad. It could be inaccurate as measured in meters.
Your relative accuracy will still be very good. Relative accuracy or accuracy of scale means does the line on earth that measures 1.001 feet measure 1.001 feet in my map.

If you choose to get a GNSS receiver, get an Emlid over the DRTK. The Emlid units are lower cost, more accurate/precise and allow for more options.

To be more versatile, a subscription to an RTK or VRS service can allow you to receive corrections to both your drone or GNSS receiver and allow for centimeter accuracy in covered areas.

There are a lot of variables and different workflows to obtain the coveted centimeter accuracy, but they all involve costly hardware and/or subscriptions and learning.

 

[Dogpilot]

I agree the Emlid is a better choice. The D-RTK-2 has monkey simple workflow if total accuracy is not paramount. Emild requires a bit of practice and/or somebody to instruct you the first few times. Getting a NTRIP/CORS account is best, but some spots suffer from virtually no coverage. Kind of my problem. Earthscope does have a free service but do not expect any customer service. Very user unfriendly. If you pay Hexagon/Leica you get excellent service. My AZCORS account works like a dream the folks are nice and helpful, but has a huge hole in Northern Arizona coverage. No cell service either.

 

[rfb]

Yes, if you just use the DRTK to obtain its coordinates while not receiving corrections or being placed on a known point, your absolute accuracy will be bad. It could be inaccurate as measured in meters.
Your relative accuracy will still be very good. Relative accuracy or accuracy of scale means does the line on earth that measures 1.001 feet measure 1.001 feet in my map.

If you choose to get a GNSS receiver, get an Emlid over the DRTK. The Emlid units are lower cost, more accurate/precise and allow for more options.

To be more versatile, a subscription to an RTK or VRS service can allow you to receive corrections to both your drone or GNSS receiver and allow for centimeter accuracy in covered areas.

There are a lot of variables and different workflows to obtain the coveted centimeter accuracy, but they all involve costly hardware and/or subscriptions and learning.

Thank you jaja6009 and Dogpilot for the explanation!

I do have some other questions about GNSS receivers if you don't mind:

1. Can I do RTK and PPK with both the Emlid and the DRTK2 base? Can I also collect GCPs with them?

2. Are there any Gnss receivers like Trimble DA2 that can collect GCPs with high accuracy (1-2cm) without a base or Cors Station?

3. Do I need to known the coordinates before usind Emlid for PPK? For instance, can I set up the Emlid base and let it collect information for a couple of hours while I do the mapping with the Mavic 3E, then process the point and adjust the images in post? Is that worflow possible? Or do I have to enter the known point in the base stations in order to use it for PPK?

I am still trying to learn basic stuff, thank you for your time!

 

[Dogpilot]

Thank you jaja6009 and Dogpilot for the explanation!

I do have some other questions about GNSS receivers if you don't mind:

1. Can I do RTK and PPK with both the Emlid and the DRTK2 base? Can I also collect GCPs with them?

2. Are there any Gnss receivers like Trimble DA2 that can collect GCPs with high accuracy (1-2cm) without a base or Cors Station?

3. Do I need to known the coordinates before usind Emlid for PPK? For instance, can I set up the Emlid base and let it collect information for a couple of hours while I do the mapping with the Mavic 3E, then process the point and adjust the images in post? Is that worflow possible? Or do I have to enter the known point in the base stations in order to use it for PPK?

I am still trying to learn basic stuff, thank you for your time!

Placing any of these over a known point is best. What they get on their own, without being connected to the NTRIP network, will vary a bit. In my personal experience, using the D-RTK-2 unit, placed over a known point with the highest level of survey accuracy (points all have differing levels of confidence based on how they where surveyed in in the first place). I was able to close a survey with .1 meter accuracy routinely. When I placed the D-RTK-2 over a random location, offset 3 km from the same high confidence survey point, I was getting .2-.4 meter accuracy. Not anything like the 5 meters talked about. Heck my handheld Garmin in reach does better than 5 meters. The Emilid should better this, but not drastically so, especially if it is at a random location, not a control point with the corrections entered. These all have various errors in the many variables. If you go onto Emily's web page they show errors you should see with their units and other manufactures units. They are not the best, but rather the best price point. I only got the D-RTK-2 because I was able to purchase mine for less than an Emilid. Shopping around and buying used will get you a deal. Ease of use, well there is a learning curve on all of them. Getting PPK data also depends a bit on your unit and to my understanding a bit of offset from the station you are using the corrections of. I don't need to be that accurate, and my testing showed it was fine for my work (not laying out foundations or the like). I do geological research.

If you can get a NTRIP account and have good signal and close to one of the transmitting stations, you can get away without needing a base station. Again, Earthscope is free access to a network. Many states also have a network you can get free access to, sometimes it is through the DOT, in AZ's case DOT transferred the network to the water department, still giving free access. You just have to ask. IN Brazil you may have to ask at the agency with governance over mapping, they may know as well. Worldwide there are far more stations than are talked about. You can also get a list of known control points from them.

I don't know if you ever read this thread, but it gives a lot of background on using any system:

Alternatives to D-RTK-2

 

[jaja6009]

Thank you jaja6009 and Dogpilot for the explanation!

I do have some other questions about GNSS receivers if you don't mind:

1. Can I do RTK and PPK with both the Emlid and the DRTK2 base? Can I also collect GCPs with them?

2. Are there any Gnss receivers like Trimble DA2 that can collect GCPs with high accuracy (1-2cm) without a base or Cors Station?

3. Do I need to known the coordinates before usind Emlid for PPK? For instance, can I set up the Emlid base and let it collect information for a couple of hours while I do the mapping with the Mavic 3E, then process the point and adjust the images in post? Is that worflow possible? Or do I have to enter the known point in the base stations in order to use it for PPK?

I am still trying to learn basic stuff, thank you for your time!

I do not own a DRTK and did not buy one due to the Emlid units offering better everything. The Emlid's GNSS chip is a better unit. Emlid has free point collection and PPK software. Emlid offers free Caster service where you can buy two Emlid units, setup one on a known point (NGS monument or your own) and then send NTRIP corrections to your hearts desire. Emlid has a full support forum where professionals respond to any inquiry within a day or two and will even help explain other helpful information like coordinate and datums.


Your questions.

1. With the Emlid units yes you can do RTK and PPK. I think you can with the DRTK (You will have to be able to download the RINEX logs) Emlid has its own PPK software that is very easy to use and was made for drone mappers. You can easily collect GCPs and Check Points with an Emlid with its easy to use, free data collection software. The newest Emlid unit RS3 also has tilt compensation which can help to speed up collection.

2. Trimble, Javid, Topcon etc. are higher end than both the Emlid and D RTK. Emlid and D RTK are lower price. Yes the highend Trimble and other can collect GCPs. They tend to have harder to use software that may or may not need another subscription or purchase.

3. This is a question that depends on your project. If your project needs low centimeter accuracy than you will have to be receiving corrections. If you just let it sit and average you will NOT have low centimeter accuracy. If you are going the route of spending big bucks for GNSS gear, do it right and get the most accuracy you can. Any project I do whether it requires low centimeter accuracy or not gets it. That way any time I revisit a site my maps will always overlay each other. and have abosulte accuracy so they can overlay other data such as plans, surveys and such. But your clients needs and project may differ. Nothing looks more unprofessional than having two maps of the same area have a shift to them.


I know that RTK subscriptions are expensive, but you do have options if you cannot afford it.

Option 1
Setup your Base on an NGS monument (Link: ArcGIS Web Application).
Have the Base send corrections to your rover on site. Mark COntrol Points. Have Base Send corrections to drone. This should be less than 20 km away.

Option 2
Same as Option 1, but Have the Rover make a known Point on site collect this point for at least 10 minutes for safety. Then do it again.. Now You can setup a Base on site to send corrections to the Rover for Control Points or the Drone.

Option 3
Setup a Base on Site a day or two before. Log for 12 hours. Run the Logs either through OPUS (Free) or use Emlid PPK software. You now have a known point to setup your Base on site. It is better to wait 24 hours when using OPUS so you have the actual satellite tracks instead os estimated. NGS has the free logs from the PPK CORS stations and they are easy to download.

Option 4
A day or two before setup a Base on Site and log. Use Rover to collect GCPs. PPK both the Base's Position and then correct the Rovers collection data with PPK.

Option 5

If you map locally make a known point at your house/office using PPK or OPUS. Setup an Emlid as a full time Base. Send corrections over NTRIP using Emlids free Caster software. Map away to your hearts desire!

Option 6
Rock RTK has a dirt cheap RTK subscription service. But if you buy a $700 base and set it up on your roof for the Rock RTK network to use, you will have free access to it. I have tested this in my area and it is okay. It is not as accurate as my other RTK service, but is not bad. THeir pricing is around $50 per month.

Option 7
Use Point One RTK subscription. A big problem is that they broadcast NTRIP in WGS 84 which is most likely not what most clients want their data in. You would have to transform both horizontal and vertical.

There are more options, but these shoudl suffice for most use cases.

Be aware of what datum any RTK service is sending corrections in. Most popular ones use NAD83(2011) with ellipsoid elevations. But some do not.

Another tip is collect everything in the same datum. Example: Collect the drone images in NAD83(2011) with ellipsoid, and then collect your Control points in the same. Then use Pix4D or Agisoft to apply the geoid. This helps to prevent any confusion when collecting in geographic coordinates vs projections.

 

[rfb]

I do not own a DRTK and did not buy one due to the Emlid units offering better everything. The Emlid's GNSS chip is a better unit. Emlid has free point collection and PPK software. Emlid offers free Caster service where you can buy two Emlid units, setup one on a known point (NGS monument or your own) and then send NTRIP corrections to your hearts desire. Emlid has a full support forum where professionals respond to any inquiry within a day or two and will even help explain other helpful information like coordinate and datums.


Your questions.

1. With the Emlid units yes you can do RTK and PPK. I think you can with the DRTK (You will have to be able to download the RINEX logs) Emlid has its own PPK software that is very easy to use and was made for drone mappers. You can easily collect GCPs and Check Points with an Emlid with its easy to use, free data collection software. The newest Emlid unit RS3 also has tilt compensation which can help to speed up collection.

2. Trimble, Javid, Topcon etc. are higher end than both the Emlid and D RTK. Emlid and D RTK are lower price. Yes the highend Trimble and other can collect GCPs. They tend to have harder to use software that may or may not need another subscription or purchase.

3. This is a question that depends on your project. If your project needs low centimeter accuracy than you will have to be receiving corrections. If you just let it sit and average you will NOT have low centimeter accuracy. If you are going the route of spending big bucks for GNSS gear, do it right and get the most accuracy you can. Any project I do whether it requires low centimeter accuracy or not gets it. That way any time I revisit a site my maps will always overlay each other. and have abosulte accuracy so they can overlay other data such as plans, surveys and such. But your clients needs and project may differ. Nothing looks more unprofessional than having two maps of the same area have a shift to them.


I know that RTK subscriptions are expensive, but you do have options if you cannot afford it.

Option 1
Setup your Base on an NGS monument (Link: ArcGIS Web Application).
Have the Base send corrections to your rover on site. Mark COntrol Points. Have Base Send corrections to drone. This should be less than 20 km away.

Option 2
Same as Option 1, but Have the Rover make a known Point on site collect this point for at least 10 minutes for safety. Then do it again.. Now You can setup a Base on site to send corrections to the Rover for Control Points or the Drone.

Option 3
Setup a Base on Site a day or two before. Log for 12 hours. Run the Logs either through OPUS (Free) or use Emlid PPK software. You now have a known point to setup your Base on site. It is better to wait 24 hours when using OPUS so you have the actual satellite tracks instead os estimated. NGS has the free logs from the PPK CORS stations and they are easy to download.

Option 4
A day or two before setup a Base on Site and log. Use Rover to collect GCPs. PPK both the Base's Position and then correct the Rovers collection data with PPK.

Option 5

If you map locally make a known point at your house/office using PPK or OPUS. Setup an Emlid as a full time Base. Send corrections over NTRIP using Emlids free Caster software. Map away to your hearts desire!

Option 6
Rock RTK has a dirt cheap RTK subscription service. But if you buy a $700 base and set it up on your roof for the Rock RTK network to use, you will have free access to it. I have tested this in my area and it is okay. It is not as accurate as my other RTK service, but is not bad. THeir pricing is around $50 per month.

Option 7
Use Point One RTK subscription. A big problem is that they broadcast NTRIP in WGS 84 which is most likely not what most clients want their data in. You would have to transform both horizontal and vertical.

There are more options, but these shoudl suffice for most use cases.

Be aware of what datum any RTK service is sending corrections in. Most popular ones use NAD83(2011) with ellipsoid elevations. But some do not.

Another tip is collect everything in the same datum. Example: Collect the drone images in NAD83(2011) with ellipsoid, and then collect your Control points in the same. Then use Pix4D or Agisoft to apply the geoid. This helps to prevent any confusion when collecting in geographic coordinates vs projections.

Amazing, thank you so much for taking the time to explain all these options! They certainly helped me better understand how this universe works. I'll definitely look into Emlid.

Have a great day!