I have the Phantom 4 RTK.  Ive set it up and flown it, but I am trying to figure out how to set the base station so that the corrections it is sending to the drone are correct.  How do I do that?  I have a known point where I can position the base, but I am not sure how to position the base and enter the correction measurements manually.  I have not found any info on how to do this for this hardware specifically.  Other hardware (cuch as Emlid Reach, etc) tell about the theroy, but no methods or SOPs for doing it with the RTK. If I simply set up the base and let it run, how does it know what to correct?

As a follow up,  Im not a surveyor, Ive got the P4RTK and I'm trying to do away with placing GCPs. I am not sure how to tell my DRTK base unit where it is and what the offset is. My literature that came with it did not say anything about inputting location info...just setting it up, linking and flying. Where's the other info? Regards, Mike in Arlington

mikesobola@veri Posted at 1-23 19:54
As a follow up,  Im not a surveyor, Ive got the P4RTK and I'm trying to do away with placing GCPs. I am not sure how to tell my DRTK base unit where it is and what the offset is. My literature that came with it did not say anything about inputting location info...just setting it up, linking and flying. Where's the other info? Regards, Mike in Arlington

Go into advanced settings under rtk and scroll down to bottom and find input gnss coordinates. Type in lat long ortho height in meters. I learned today that the ortho height needs to be set to the center of the antenna and not the point at which you have the base set on. Approx 5.8 feet. There is also a major pix4d update that was released 23 January that fixed a major problem with this using the p4rtk. Hope this helps.

tony anderson Posted at 1-25 18:32
Go into advanced settings under rtk and scroll down to bottom and find input gnss coordinates. Type in lat long ortho height in meters. I learned today that the ortho height needs to be set to the center of the antenna and not the point at which you have the base set on. Approx 5.8 feet. There is also a major pix4d update that was released 23 January that fixed a major problem with this using the p4rtk. Hope this helps.

Thanks, Tony. Unfortunately, the controller does not allow me to input anything.  In addition, I live in VA where we have to input negative values. The app does not allow this yet.  A known DJI bug,.  I have decided to connect to the TOPCON network and not use the base station.  No GCPs needed. TOPCON is realtime and spot on.
Sucks to have to do this.  DJI sold this under false pretenses.

mikesobola@veri Posted at 1-25 18:41
Thanks, Tony. Unfortunately, the controller does not allow me to input anything.  In addition, I live in VA where we have to input negative values. The app does not allow this yet.  A known DJI bug,.  I have decided to connect to the TOPCON network and not use the base station.  No GCPs needed. TOPCON is realtime and spot on.
Sucks to have to do this.  DJI sold this under false pretenses.

“DJI sold this under false pretenses.”

I think more and more people are going to realize this. To get real accuracies need to turn off RTK and post-process your logs. You can then manually input your known base station coordinate.

mikesobola@veri Posted at 1-25 18:41
Thanks, Tony. Unfortunately, the controller does not allow me to input anything.  In addition, I live in VA where we have to input negative values. The app does not allow this yet.  A known DJI bug,.  I have decided to connect to the TOPCON network and not use the base station.  No GCPs needed. TOPCON is realtime and spot on.
Sucks to have to do this.  DJI sold this under false pretenses.

I HAD THE SAME PROBLEM TRYING TO INPUT A NEGATIVE LONGITUDE AND THE DEC 5 UPDATE TO THE REMOTER CONTROLLER FIXED THAT PROBLEM..  I AM ABLE TO INPUT MY GNSS LAT LONG AND ORTHO HEIGHT THEN PRESS SETTINGS AND IT SAYS SUCCESFUL.  WORKS FINE FOR ME.  HOPE THIS HELPS..

DroneRunnerPlus Posted at 1-26 05:18
“DJI sold this under false pretenses.”

I think more and more people are going to realize this. To get real accuracies need to turn off RTK and post-process your logs. You can then manually input your known base station coordinate.

I WAS ABLE TO SET MY DRTK 2 BASE ON A KNOWN CONTROL POINT AFTER GETTING ALL OF THE LATEST UPDATES INSTALLED AND IT WORKED FINE.  THE ONLY THING YOU NEED TO REMEMBER IS WHATEVER THE ELEVATION OF YOUR CONTROL POINT IS THEN YOU NEED TO ADD 5.83 FEET TO THE ELEVATION BECAUSE DJI IS USING THE CENTER OF THE ANTENNA HEIGHT AND NOT THE CONTROL POINT ITSELF.  I WISH I KNEW THE EXACT DISTANCE TO THE CENTER OF THE ANTENNA BUT 5.83 FEET IS WORKING VERY WELL.  MY CELL IS 479-462-4861 IF ANYONE HAS ANY QUESTIONS..

tony anderson Posted at 1-26 07:24
I WAS ABLE TO SET MY DRTK 2 BASE ON A KNOWN CONTROL POINT AFTER GETTING ALL OF THE LATEST UPDATES INSTALLED AND IT WORKED FINE.  THE ONLY THING YOU NEED TO REMEMBER IS WHATEVER THE ELEVATION OF YOUR CONTROL POINT IS THEN YOU NEED TO ADD 5.83 FEET TO THE ELEVATION BECAUSE DJI IS USING THE CENTER OF THE ANTENNA HEIGHT AND NOT THE CONTROL POINT ITSELF.  I WISH I KNEW THE EXACT DISTANCE TO THE CENTER OF THE ANTENNA BUT 5.83 FEET IS WORKING VERY WELL.  MY CELL IS 479-462-4861 IF ANYONE HAS ANY QUESTIONS..

It would be nice to be able to enter the pole height separately like every other GNSS system out there. Just curious what size of sites do you fly? I have spoken with several P4P RTK users and they are having trouble maintaining an RTK fix when they get past 350-400m. I can maintain VLOS up to about 800m... This is another reason for PPK because you can then use the base log and Distance To Base (DTB) to turn those floats into a fix.

I updated the controller and still could not input data.   I am abandoning the base station because my who reason for buying the RTK was to do away with GCPs.  I figured out that I can connect to the TOPCON network and receive corrections that way instead of having to input known points into the base station.  I am trying to eliminate GCPs. That's the whole point of the aircraft.

DroneRunnerPlus Posted at 1-26 05:18
“DJI sold this under false pretenses.”

I think more and more people are going to realize this. To get real accuracies need to turn off RTK and post-process your logs. You can then manually input your known base station coordinate.

I figured out that I can connect to the TOPCON network and receive corrections that way instead of having to input known points into the base station.  I am trying to eliminate GCPs. That's the whole point of the aircraft.  Drone Deploy just came out with a paper where they test the drone on a network (not the base station) and it is spot on accurate.

mikesobola@veri Posted at 1-26 09:07
I updated the controller and still could not input data.   I am abandoning the base station because my who reason for buying the RTK was to do away with GCPs.  I figured out that I can connect to the TOPCON network and receive corrections that way instead of having to input known points into the base station.  I am trying to eliminate GCPs. That's the whole point of the aircraft.

Can you explain the steps to dial up using a vrs network. I just need to know if I can use my iPhone as a portable hotspot or do I need to get a mifi. I think I can figure out the dji controller except for what you type under mountpoint. Thanks much

mikesobola@veri Posted at 1-26 09:09
I figured out that I can connect to the TOPCON network and receive corrections that way instead of having to input known points into the base station.  I am trying to eliminate GCPs. That's the whole point of the aircraft.  Drone Deploy just came out with a paper where they test the drone on a network (not the base station) and it is spot on accurate.

Yeah, I read that and will be asking them a few questions about some of the wording. No doubt it will be better that a P4 Pro without GCP's, but I have been working with them in the different scenarios for almost two years and there is allot of marketing mispeak going on around this drone and I want to make sure people understand that,

(1) The 5cm accuracy is +/- which could equal 10cm across a site
(2) Accuracies reported are map relative, not absolute accuracy compared to the ground
(3) Unless you setup on and manually configure to a known point you will not match design data without work in external applications.
(4) Setting up on a known point still does not ensure that you are properly rotated.
(5) For 2nd order high accuracies you should turn off RTK and post-process the data, including updating the geotags of the images.
(6) For 1st order highest accuracy you should still use at least 3 GCPs and PPK.

Please do your homework before you get oversold.

tony anderson Posted at 1-26 11:19
Can you explain the steps to dial up using a vrs network. I just need to know if I can use my iPhone as a portable hotspot or do I need to get a mifi. I think I can figure out the dji controller except for what you type under mountpoint. Thanks much

I use my Samsung as a hot spot.  You use yhe following settings in the "Custom" RTK dropdown.  (I think there are three options: "none", "DRTK-2"-or whatever the mobile network option is- and "Custom").  You select custom and then you should get another page or dropdown where you put in the following:
Ntrip Host: (You get this from your TOPCON or network provider when you buy the service)
Port: 8008
User Name: (You get this from your TOPCON or network provider when you buy the service)
PW: (from your provider)
Mount Point: RTK_RTCM3 or NETRTK_RTCM3 (both of these work for me).

The company that sold me the RTK Drone is also providing me the network connectivity.  I bought the "pay-as-you-go" option.  It's only $160 for 40 hours of connectivity time.  Very cheap.  The clock is only clicking when you are logged in and using the service.

I hope this is what you were looking for.

CHASCOADMIN Posted at 1-26 13:12
Yeah, I read that and will be asking them a few questions about some of the wording. No doubt it will be better that a P4 Pro without GCP's, but I have been working with them in the different scenarios for almost two years and there is allot of marketing mispeak going on around this drone and I want to make sure people understand that,

(1) The 5cm accuracy is +/- which could equal 10cm across a site

First off, they sold it as ABSOLUTE accuracy within 5cm without control points.
Its nowhere near that.  In fact, it's impossible for the base station to correct for inaccuracies if it doesn't know where it is!

The TOPCON network connection is spot on correct without GCPs.  Don't need them. Throw that base station in the garbage.  It's absolute accuracy with less than an inch variation as compared to surveyed results.  

mikesobola@veri Posted at 1-26 14:35
I use my Samsung as a hot spot.  You use yhe following settings in the "Custom" RTK dropdown.  (I think there are three options: "none", "DRTK-2"-or whatever the mobile network option is- and "Custom").  You select custom and then you should get another page or dropdown where you put in the following:
Ntrip Host: (You get this from your TOPCON or network provider when you buy the service)
Port: 8008

Thanks mike. BTW my p4rtk fell out of the sky last Sunday from 50 meters up with 31 percent battery. It was in Return to home mode after low battery warning then 1second later I got critical battery message and it fell out of the sky. Apparently it’s happening the same way to others as well. Lucky for me I was at a school playground testing the accuracy of gcps and no one was around.

mikesobola@veri Posted at 1-26 14:38
First off, they sold it as ABSOLUTE accuracy within 5cm without control points.
Its nowhere near that.  In fact, it's impossible for the base station to correct for inaccuracies if it doesn't know where it is!

@mikesoboloa

I can't tell if you are agreeing or not? Actually they sell it as global accuracy and that is even different from relative or absolute.

Global = Wherever the satellites tell it according to WGS84 coordinates and how well the finished map/model represents that.
Relative = The relationship of point A to point B with regards to how that relationship is on the ground.
Absolute = Direct comparison of the coordinate values to the ground. If I make a surface of the point cloud from the drone I can guarantee you that it will never stakeout to that tolerance.

The base station knows where it is if you tell it where it is with a known point. If not then that is why people will need to learn PPK. Even if you are on a network you should use PPK just to correct the drone. Also, using PPK you can define the coordinates of the base. This is an important factor when trying to localize the site control as it may have a scale factor or be shifted from the global position.

Lastly, there are several factors in the DroneDeploy study that are not good representations of reality.
(1) It's one controlled test.
(2) It's a very small site.
(3) The elevations were determined by a calibration point in their software.
(4) The flight altitude was only 55m which is not practical for most mapping missions.

tony anderson Posted at 1-26 15:00
Thanks mike. BTW my p4rtk fell out of the sky last Sunday from 50 meters up with 31 percent battery. It was in Return to home mode after low battery warning then 1second later I got critical battery message and it fell out of the sky. Apparently it’s happening the same way to others as well. Lucky for me I was at a school playground testing the accuracy of gcps and no one was around.

Ugh. That is awful. Sorry.  Do you think it is the battery batch?  I almost had that happen a few months ago with my P4P but it was a knock off battery.  I bought an off-brand and it went from 75% to Critical to "land immediately".  I was able to land. Never used the batteries again (I had two and it also happened with the second one).

CHASCOADMIN Posted at 1-26 15:40
@mikesoboloa

I can't tell if you are agreeing or not? Actually they sell it as global accuracy and that is even different from relative or absolute.

Ugh.
This is depressing. I am just trying to figure out how to get what I paid for.  My dealer is a surveyor and he told me that using the network, he was able to get accuracy within less than a fraction of an inch.  He laid down GCPs only to test the validity of the data coming from the drone and network.  I was under the impression that the network sent real time corrected data.  Of course, I'm not a surveyor and I don't have a background in GIS. I'm a TV Producer-turned Drone Pilot trying to get accurate data from my drone.  Its all so confusing, just trying to muddle through.  So, you would suggest using the network and a known point?  What if I use the base station on the known point-would't that be the same thing?

M

mikesobola@veri Posted at 1-26 17:14
Ugh.
This is depressing. I am just trying to figure out how to get what I paid for.  My dealer is a surveyor and he told me that using the network, he was able to get accuracy within less than a fraction of an inch.  He laid down GCPs only to test the validity of the data coming from the drone and network.  I was under the impression that the network sent real time corrected data.  Of course, I'm not a surveyor and I don't have a background in GIS. I'm a TV Producer-turned Drone Pilot trying to get accurate data from my drone.  Its all so confusing, just trying to muddle through.  So, you would suggest using the network and a known point?  What if I use the base station on the known point-would't that be the same thing?

As a surveyor using gps daily we have better accuracies the closer the control is to the site so I am going to keep using the base setup on a known point. It really depends on what kind of vrs network you have. We have one in my area that only extends out about 15 miles from the permanent base station to achieve factory specs on accuracy. The farther you are from the base the less accurate it becomes. I wouldn’t give up on the DRTK base yet as it takes some trial and error to get all the bugs out eventually.

tony anderson Posted at 1-26 18:26
As a surveyor using gps daily we have better accuracies the closer the control is to the site so I am going to keep using the base setup on a known point. It really depends on what kind of vrs network you have. We have one in my area that only extends out about 15 miles from the permanent base station to achieve factory specs on accuracy. The farther you are from the base the less accurate it becomes. I wouldn’t give up on the DRTK base yet as it takes some trial and error to get all the bugs out eventually.

Thanks.  I'm just a Producer-turned-Drone Pilot trying to figure this all out.  I get different stories everywhere.  I am trying to eliminate the GCPs, but I can usually set up on a known point on my construction sites without much problem.  I think I'll do that and use the network with the known point.  Start using the DRTk-2 base once kinks get worked out.

M

Surveyor here too. A base and rover (drone) setup will Always be more relatively accurate. CORS and VRS are more globally accurate according to the authority operating them because all their networks tie together. What your dealer said is misleading and easy to misunderstand. No aerial system can produce absolute accuracies which is what most people think they are getting, in fractions of an inch. He was probably talking about the RMSE values of the camera positions and the relative accuracy of the map.

All of this being said it really depends on what your end goal is and what kind of information you are trying to provide. Some people are ok with just the map and relative progress figures including stockpile take offs. My end goal is to provide data that directly integrates with our design and CAD files that are based on local benchmarks so that I can integrate everything together. This is where the base station on a known local coordinate comes into play. Next you get to learn about projections, state plane coordinates and scale factors. I’m new to this forum, but I have been part of several others and PPK drone surveying for a while and am always happy to help if you want to PM me. I would suggest checking out forum.dronedeploy.com and community.emlid.com for a little information more relevant to gps, drones and mapping.

I will say one more quick thing. Anyone that is actually surveying with a drone (not just mapping) that wants to get serious repeatable accuracies are fooling themselves if they think they’re going to completely get away from GCP’s. No offense of course. You get a hall pass your freshman year.

tony anderson Posted at 1-26 07:24
I WAS ABLE TO SET MY DRTK 2 BASE ON A KNOWN CONTROL POINT AFTER GETTING ALL OF THE LATEST UPDATES INSTALLED AND IT WORKED FINE.  THE ONLY THING YOU NEED TO REMEMBER IS WHATEVER THE ELEVATION OF YOUR CONTROL POINT IS THEN YOU NEED TO ADD 5.83 FEET TO THE ELEVATION BECAUSE DJI IS USING THE CENTER OF THE ANTENNA HEIGHT AND NOT THE CONTROL POINT ITSELF.  I WISH I KNEW THE EXACT DISTANCE TO THE CENTER OF THE ANTENNA BUT 5.83 FEET IS WORKING VERY WELL.  MY CELL IS 479-462-4861 IF ANYONE HAS ANY QUESTIONS..

Are you able to share where you got the information for using 5.83ft? I've been searching Antenna Phase Center information but haven't been able to find anything.

BEO Posted at 2-27 08:58
Are you able to share where you got the information for using 5.83ft? I've been searching Antenna Phase Center information but haven't been able to find anything.

Lots of info in this thread here.

patiam Posted at 2-27 09:59
Lots of info in this thread here.

Yep I am came across that thread right after posting my comment here. Just finished reading through the whole thing. Thank you!

tony anderson Posted at 1-26 11:19
Can you explain the steps to dial up using a vrs network. I just need to know if I can use my iPhone as a portable hotspot or do I need to get a mifi. I think I can figure out the dji controller except for what you type under mountpoint. Thanks much

Hello Tony,

You can use your phone for a hotspot but I would be careful of doing that.  If you can take phone calls and use data at the same time,  it's probably fine.  For me,  on Sprint,  if I take a phone call while a flight is in progress, my data drops and the RTK will also drop.  I use a dedicated hotspot for the drone instead of my phone.

Eric W.

ewischropp Posted at 3-10 16:57
Hello Tony,

You can use your phone for a hotspot but I would be careful of doing that.  If you can take phone calls and use data at the same time,  it's probably fine.  For me,  on Sprint,  if I take a phone call while a flight is in progress, my data drops and the RTK will also drop.  I use a dedicated hotspot for the drone instead of my phone.

get a better phone/plan.
or like you said, use a dedicated hotspot.

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