How to Use RTK

[andrew124C41]

I am about to purchase a new E2PV3 after my V2 flew off. It appears that for me to get the larger SC the cheapest way is to get the RTK version. I have done some mapping and have thought about getting my part 107 equivalent and learning and doing more mapping. I did some with the V2 and enjoyed it. If I don't, I can just remove the module.

I have a very rudimentary knowledge of how RTK works but I don't know enough about the details.

What other equipment do I need to connect the drone to a server? I have some amateur radio VHF and UHF equipment but have no idea they cover the same frequencies.

In addition to other equipment, are there public servers or does one pay for a subscription and if so, how much does it cost?

Any references would be appreciated.

 

[Dave Pitman]

I have a very rudimentary knowledge of how RTK works but I don't know enough about the details.

How RTK works is fairly straight forward. Understanding the nuances of the geodesy is deep and vast. To simply fly an RTK equipped Evo in RTK, you will need either an NTRIP service, or a precision GNSS on site that can broadcast NTRIP, and perhaps a known benchmark at the location that you can use to orient your gnss receiver.

Autel EVO II Enterprise and Reach RS2/RS2+ base integration | Reach RS2/RS2+

This guide shows how to set up Reach RS2/RS2+ as a base for the Autel EVO II Enterprise drone to geotag drone images for further mapping in photogrammetry software.

docs.emlid.com

 

[camazu]

How RTK works is fairly straight forward. Understanding the nuances of the geodesy is deep and vast. To simply fly an RTK equipped Evo in RTK, you will need either an NTRIP service, or a precision GNSS on site that can broadcast NTRIP, and perhaps a known benchmark at the location that you can use to orient your gnss receiver.

Autel EVO II Enterprise and Reach RS2/RS2+ base integration | Reach RS2/RS2+

This guide shows how to set up Reach RS2/RS2+ as a base for the Autel EVO II Enterprise drone to geotag drone images for further mapping in photogrammetry software.

docs.emlid.com

I second @Dave Pitman and the link he provided. If you are in the construction world, I would also suggest that you speak with your surveyor about local controls and state planes (if in the United States).

 

[curd1]

I am in a state with an NTRIP network that covers the whole state. I had to make a free account and get the logon information and mountpoints from the state agency that controls the system. When I go to map a site, I have to have cell service, that is the only caveat of the public NTRIP network. Hasn't been an issue yet with me. I get my smart controller connected to my cell phone hotspot and then enter the login information on the controller, in the camera settings under RTK. When you connect, you should see accuracy of around 1-2 cm. There is also an "RTK lock" logo on the main viewer as well with # of satellites displayed. Now your coordinates written to the images should be accurate to cm level.

I process photos using Reality Capture. I've used Agisoft as well. Both of these programs you have to tell the coordinates are RTK, otherwise it will assume large uncertainties in each camera position. I am not knowledgable of the PPK workflow.

Please someone correct me if I should be doing something differently. I work in the local coordinate system of my model so I do not know much about global coordinates.

 

[CW3Drones]

Thank you for this information. I have an Autel V3 RTK Drone and access to NTRIP through Missouri DOT. I think I understand now why I get the RTK not ready notification.
I’ll connect my SmartController to my cellphone and then work to ensure I have the correct information in the RTK screen. I think, like many new RTK pilots, I’m looking for a less expensive alternative to purchasing a Base Station and other equipment before I even get a client who wants or needs the level of accuracy that would justify the cost. Plus, I’m still just learning!
-

 

[Dfly]

Thank you for this information. I have an Autel V3 RTK Drone and access to NTRIP through Missouri DOT. I think I understand now why I get the RTK not ready notification.
I’ll connect my SmartController to my cellphone and then work to ensure I have the correct information in the RTK screen. I think, like many new RTK pilots, I’m looking for a less expensive alternative to purchasing a Base Station and other equipment before I even get a client who wants or needs the level of accuracy that would justify the cost. Plus, I’m still just learning!
-

I’m in the same boat, only I don’t even have an RTK version yet…Nice to know that, with reliable network access, one can get pretty accurate maps this way. I’d imagine that relative accuracy within the map would be improved as well.

 

[robport]

Me too. I just bought a used RTK module off ebay for my Evo II Enterprise. I connected to Pointone Nav and ran a short test last weekend. On the RTK screen, I was reading 3-4 centimeters standard deviation in the X and Y and 10 in the Z axis. The map I got wasn't even close to the google map. I was thinking it would be a few feet off at most, but this is at least 10 feet off in one direction and 3 feet in the other. This is about how it would look without the RTK module, actually worse. It was processed in opendronemap and I dropped the opacity so it would be easier to see how they don't match up. Anyone know what other steps I could have missed? Is there something else I have to do to get the correct GPS coordinates on the pictures?

 

[EBERLS]

If your trying to compare your data (with the accuracies you are stating in your imagery) in Google Earth imagery it's a waste of time. A lot of GE data is based supposedly in WGS84 datum. Their imagery is good for looking at places and reviewing where you live and using as a guide but that's about it.. There have been maybe a handful of times when I've attempted what you're doing and that it lined up fairly well, but that's because GE imagery was using our county supplied imagery. Really, there's no information where their data has come from or what datum/projection the original imagery was in.

I use GE mostly for preliminary research for survey projects. I can re-project twist and rectify GE imagery based on our "on the ground" located survey data, i.e. road intersections, sidewalk corners, road markings etc. but 99%of the time it's only accurate +/- 1'.

All our mapping and survey data is referenced to the NSRS (National Spatial Reference System, state plane coordinate system). Overlaying a GE image after re-projection to the NSRS usually results in a 1-2 meter error in reference to our ground control data. Even rectifying the GE imagery (rubber sheeting) to our data usually results in a 0.2-0.5m error. A lot of the error usually comes from the original supplier, then GE attempts to fit it in their system and a lot of times it's manually forced to fit adjoining imagery .

If I need accurate imagery, we fly it ourselves. To me GE imagery is great to look at and use in preliminary research but that's about it.

 

[jaja6009]

Robport,

Goto your county GIS or what ever state environmental agency you have since they usually have some good data.

Find a more authoritative map in your state's projected datum/coordinate system. Import it into QGIS, Arc Pro or Global mapper. Then process your map in the same and see how it lines up (Arc Pro with transform on the fly if you have it in a different datum, but this slows down computers lacking RAM and CPU). You could also do this with the dense point cloud if you can get some authoritative LiDAR data.

I have a beach project where I cannot properly lay out Check Points due to people stepping on/moving or downright stealing them, so for my checks I overlay my Dense Point cloud in Cloud Compare or QT reader and check it against authoritative state LiDAR.

As stated, Google Earth can be pretty inaccurate and also in a different datum.

Also what datum does Point 1 use? I could of swore they use WGS84 for sending corrections, can you confirm this please?

 

[robport]

Robport,

Goto your county GIS or what ever state environmental agency you have since they usually have some good data.

Find a more authoritative map in your state's projected datum/coordinate system. Import it into QGIS, Arc Pro or Global mapper. Then process your map in the same and see how it lines up (Arc Pro with transform on the fly if you have it in a different datum, but this slows down computers lacking RAM and CPU). You could also do this with the dense point cloud if you can get some authoritative LiDAR data.

I have a beach project where I cannot properly lay out Check Points due to people stepping on/moving or downright stealing them, so for my checks I overlay my Dense Point cloud in Cloud Compare or QT reader and check it against authoritative state LiDAR.

As stated, Google Earth can be pretty inaccurate and also in a different datum.

Also what datum does Point 1 use? I could of swore they use WGS84 for sending corrections, can you confirm this please?

I believe that's right, according to their documentation for their API.

 

[djfxall]

Me too. I just bought a used RTK module off ebay for my Evo II Enterprise. I connected to Pointone Nav and ran a short test last weekend. On the RTK screen, I was reading 3-4 centimeters standard deviation in the X and Y and 10 in the Z axis. The map I got wasn't even close to the google map. I was thinking it would be a few feet off at most, but this is at least 10 feet off in one direction and 3 feet in the other. This is about how it would look without the RTK module, actually worse. It was processed in opendronemap and I dropped the opacity so it would be easier to see how they don't match up. Anyone know what other steps I could have missed? Is there something else I have to do to get the correct GPS coordinates on the pictures?View attachment 16990

Try using Ground Constraint Points along with your mapping to verify your accuracy. Set up some point in 3 different areas that are 10 feet or meters apart measured as accurately as possible try to do it on level ground if possible.