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PPK results with Phantom 4 Pro v.2
Posted by leegreen on October 24, 2018 at 1:03 pmFor the past month I have been working with Cody Remington founder at BAAM Tech
They sell and install a $2500 PPK kit for any DJI Phantom 4 and Inspire 2. The system utilizes GPS L1/L2, GLONASS G1/G2, BeiDou B1/B2, Galileo E1/E5b and SBAS constellations. They include a software for post-processing the RINEX log files from your Survey grade base station and the log file from the sUAS system.
The process is very simple, here is a brief step by step;
- You set up your GNSS base receiver to log static data at 1-second epochs.
- Place the sUAS with PPK system on the center of the Iron Cross aerial target (supplied with the system from BAAM Tech). This stores the initial point of the PPK as your single calibration point.
- Launch your sUAS mission. The system triggers the camera to synchronize with the static log file. All static data is stored in the included USB drive on the system. The PPK receiver uses the drone power supply, so no additional charging.
- The Post-processing software from BAAM Tech computes the Lat/Lon/Ell and replaces the GeoTag for each photo of your aerial mission.
- Mark only the launch point on 5 photos in Pix4d, and process.
Here is a snippet of accuracy report from Pix4d.
Complete Pix4d report.
TJE Yogi replied 5 years ago 9 Members · 18 Replies- 18 Replies
Lee, it would be worthwhile repeating step 2 at the end of each flight as a check that all was well.
Lee, thanks for the information. I’m definitely interested in this. How long did your static run in the this project example? If you didn’t put out the other targets as checkpoints, you could complete this entire mission in way less than an hour. Does the static need to run for a minimum amount of time to achieve these accuracies?
Andrew,
The entire static was only 20 minutes, including the flight time. If you contact BAAM Tech, please mention my name.
If your not familiar with how PPK and Rapid Static can work together, I’ll try to explain it here.
On a project you have never visited (which is the most common) you set up your base to collect 1-second epoch static data at an unknown location. Just set a nail, this does not have to be on a target. But it is a good idea to use an aerial target since it is an easy check. This base must collect at least 15 minutes of static to send it to OPUS-RS for an accurate SPC to be computed, not hard to do.Turn on your drone, then you place it on a second aerial target, centering the camera on the target. The drone will automatically take a photo of the launch point while on the ground. This is only for calibration. The BAAM Tech system on the drone will also collect 1-second static data, and it will synchronize the clock with a much more accurate clock. The BAAM Tech system will accurately mark the exact time each photo is taken. The clock accuracy is one of the fundamental differences between mapping grade GPS and Survey grade GPS, along with added signals and frequencies. These clocks are accurate to the second of time, 8 places past the decimal. The SV’s have atomic clocks which are even more accurate. So when an epoch of data is collected it is later post-processed to compare the exact epoch with other receivers. This is how the position is calculated. You will send your Base data to OPUS-RS for an accurate State Plane coordinate. Then use you will use BAAM Techs software to post process your Base data with the Drone static data, using the coordinate of the base computed by OPUS-RS.As Chris Mills mentioned, you can also place the drone camera back over the launch point at the end of the flight mission and take a photo as a check. In fact, you could even walk the drone over to other checkpoints, place the camera directly over the point and take a photo for more checks. When you take a photo, it records a static position, just like a rover and data collector would do. The BAAM Tech antenna height is an additional 0.04m from camera to the ground. The antenna height from the camera to the phase center is 0.208m. Essentially you are using the BAAM Tech system as your GPS rover pole. I prefer to use RTK that is part of my Base Rover system to do this. But if you have only one GPS receiver and use that as a Base, the BAAM Tech System can be your survey rover. The BAAM Tech system is removable and portable. You can move it to another drone, or you could place it on a GPS rover pole to collect check points.Great Post Lee, Thank you for sharing.
Thanks for posting this Lee and once again it was good talking with you. I sent my P4P in today and am already anxiously awaiting its return.
Gregg
Very interested but worried that the dji care refresh is invalidated with this augmentation.
Lee, what kind of results do you get with zero GCPs?
Andrew,
The results I posted is virtually zero GCP’s. The drone creates the initial point, which is used for a single GCP calibration.
Just like any use of static GPS, it is very important to place your Base in an area with wide open sky. At my office, there are a lot of large White Pine trees over 80ft tall. I launched a test mission with the base getting just 5 US and 4 Glonass SV’s. The PPK post-processing produced all float positions. Rendering the data useless. But fortunately I had three GCP’s, the launch point, and two painted cross’s on pavement. Along with the BASE as a check point. This salvaged the entire project. Proving it is important to have at least three GCP’s on all projects.
Thanks Lee. I??m trying to evaluate what kind of results to expect in areas where placing targets is difficult or unsafe for various reasons.
I find that we always need to leave a few control points for a survey baseline. These points don’t need to be around the perimeter, just have them a few hundred feet apart. I like to paint a cross on the highway, leaving a PK nail in the center.
Thanks for this post. I have a question: is there a range limit from the base to where the drone is flying and what is it? Let’s say I have a 10 mile linear project and because of obstruction I can only put my base around the 1 mile maker (not the 5 mile marker), will this affect the quality of the data?
Very unwise.Comparing data quality when we have had two bases running shows that you shouldn’t really go beyond 4km. from the base position. It’s good practice to have the base within sight of the flying position.
I’m assuming you are moving up with the UAV and not simply flying beyond line of sight. If the main base is left somewhere safe for the duration of the job you should use a second base moving up with you. It will fix from the main base during the duration of each flight.
Alternatively, if you only have one base station then you might need to fix a couple more positions along the line before you do the flying.
I’m testing the use of two static Base stations (at 1 second epoch). I’m trying to figure out how to apply the corrected GeoTags with Pix4d and post-processing with Topcon Magnet Tools. This yields very good results and I find it much easier than the BAAM Tech software.
My projects are all less than 100 acres, so the base stations are not too far apart.
If the poster above is trying to use a CORS for a base, this could have two downfalls. 1) Distance is likely too far from your project. 2) Most CORS are not recording 1-second Epoch with GNSS.
It’s amazing how accurate the flight lines are with the Phantom 4 Pro v2 (without RTK). See image below.
We tend to use two base stations on linear jobs such as coastlines and pipelines, leapfrogging the units as we go along and with around 3-4km spacing maximum. The nearest base to the flight is used for the PPK. The spacing is determined by the fact that we are also using them to set GCP and check points and we don’t want the RTK dropping out during that operation. If you put the second base up first (if that makes sense) then that sits through three flights as the other base leapfrogs. By that time it should have a good fix. The remainder of the bases then fix between themselves on short lines. On a large job the last but one base can also site for three flights and provide another full fix.
Our jobs are typically larger than Lee’s sites, although not as neat and tidy – one advantage of a rotary over a fixed wing – so there is more need to have multiple base positions.
Lee, any news on how you’re getting on with the BAAM TECH please? I’m thinking of putting one on my M200.
Yes it works great. I’m flying three projects this week with it.
Is anyone having good luck with this sUAV PPK setup?
It’s been awhile since this first posted
Any updates? reviews
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