RTK UAS

pixi rtk + pixhawk autopilot looks promising.

gschrock, post: 370174, member: 556 wrote: Hi TG,

i would probably be more efficient to google "UAS RTK". There has been a tidal wave of GNSS, RTK, and GNSS-INS solutions for UAS large and small, rotor and fixed wing. While RTK might be great (but not as great as those who assert that it can completely replace ground targets) definite gains have been made from emulating what has been done for manned aircraft for man years; namely GNSS-INS systems and post-processed solutions (e.g. Applanix Pos-Av and NoivAtel SPAN to name just a few). Some if these systems have been miniaturized to fit in small (but not tiny) UAS.

RTK in a UAS has utility in live guidance of rotor craft in tight spots (but the very same tight spots might not have clear sky view... IMU improve those situations).

Stanford U and others experimented with RTK in UAS in the late 90's, and some commercial one-off designs to do things like inspect gas lines have had them all along. But it seems like every new UAS with RTK capabilities gets touted as "the first" especially ones that are late comers or that haven't actually been released yet.

If you choose criteria for the craft and payloads that suit your needs, most already have, or is almost always a another similar model out there that has RTK capabilities.

Thanks for the advise. I am trying to find a all in one package without third party RTK connections.
thanks again for our time, TG

Tgoold,

Your first question should be your estimated coverage area. The DJI multi rotor route is really only well suited for 100 acre and less jobs. Even the Phantom Pro can return excellent results, but the camera is a limitation. The Matrice 600 can obviously get you around that camera problem though.

If many of your jobs are much over 100 acres, the Ebee would would be a great choice. I really do not see the need for RTK on your drone. Ground control is always the solution for good results. My neighbor owns an Ebee I have used, and it delivers a superior product compared to my Phantom. The Ebee can not be deployed everywhere though, because of the landing method, whereas the multi rotor can much more easily complete small jobs, with virtually no location limitations.

I vote for both.

Yes the Ebee RTK is on my wish list. But as you mentioned takeoff and landing areas are limited. We are located in NW WI plenty of thick tree canopy.
I vote the same

I saw this at the surveyors conference in TN this year. Earl Dudley was selling it. Cant remember if it had rtk or not. But it is impressive.
https://www.sensefly.com/drones/albris.html

0.5km free planner, 65$ unlimited, supports different autopilots :
https://www.ugcs.com/

Aibotix X6 with RTK. Can be used as a base/rover or network rover setup.

what's the purpose why you need rtk on a UAS?adding radio component to a UAS would add to its weight which is not good since it will degrade power supply and flying time. it's not same with land survey that you need to have cm level accuracy say for setting corners etc.
you could use dual freq gps receivers and post process the images later at the office.

FrancisH, post: 387286, member: 10211 wrote: what's the purpose why you need rtk on a UAS?adding radio component to a UAS would add to its weight which is not good since it will degrade power supply and flying time. it's not same with land survey that you need to have cm level accuracy say for setting corners etc.
you could use dual freq gps receivers and post process the images later at the office.

Quite correct. The additional power does reduce the flight time by a few minutes. Screening the RTK unit from camera interference can cause problems - although the camera internals are normally well screened, the display tends to be very dirty and emit a lot of noise, so there is a risk of interfering with the RTK.

The theory is that an RTK position means that no ground control is needed and for many purposes the RTK location will tighten up the photo stitching well enough. For higher precision most clients would probably want some form of verification that the data mwas accurate. If you are going to have to walk part of the area to put in ground truth checks, then you might as well do it first and also put in proper ground control point targets.

Most of the manufacturers and software houses seem to have a rather rosy view of "accuracy": often they mean precision, which isn't the same thing. Again, mean values aren't the same as accuracy; knowing the spread you will get is just as important. Mean is fine if you are doing volumes where the variations balance out, not so good if you are surveying a highway, where variations give a bumpy ride.

RTK will enable less ground control to be put in, but ground control does tighten things up. The camera trigger needs to be exactly to the RTK timing and the offset of the camera relative to the antenna electrical centre needs to be allowed for (which means the instantaneous heading, pitch and yaw need to be accounted for). It will probably be of greater use in future when extended and beyond line of sight operations become more common.

The theory is that an RTK position means that no ground control is needed and for many purposes the RTK location will tighten up the photo stitching well enough.

where did you hear this? RTK will always need another reference station to broadcast corrections or was there a new development while I was sleeping?

The BASE station for the RTK does not necessarily have to be visible on the photography; it may even/probably be Network RTK . By "ground control" I am taking the usual meaning of the phrase - surveyed ground markers visible on the photography.

The reason various manufacturers are looking at RTK on UAV's is that they hope to be able to eliminate setting out ground markers for the photography. Setting up a base station at the flying site shouldn't be an extra burden, since you have gone there anyway. It will probably be visible on the photography, so it could be used to pin one position accurately (although getting a true height on the receiver might be a little suspect.

BUT what does RTK gain you over PPK? We fly full size aerial cameras and LiDAR units on manned aircraft everyday and ALL of that is post processed. We haven't found that the aircraft trajectory is sufficient except in cases where only "rough" products are required such as tree counts or bird counts, etc. It has never proven to be good enough to skip the ground control when you want a good relative orientation to the ground for survey accuracy topos, orthos. etc.

SHG

Tgoold, post: 370144, member: 8615 wrote: We are still in the research mode of our uas purchase. I see that DJI just launched the Matrice 600 which at some point will have RTK capabilities.

Does anyone have another solution for a RTK copter?

thanks

TG

Received an email from these folks earlier this year.
http://www.prnewswire.com/news-releases/microdrones-celebrates-part-107-with-high-value-offer-300289366.html

Shelby,

Exactly right. Ground control provides an absolute certainty amongst all the predicted and theoretical accuracies - something which has been measured rather than deduced.

I'm currently involved with a manufacturer in testing the achievable accuracies using PPK and various options for provision of reference data (on site base, offsite base, network bases). By itself the PPK can produce good results, but there is no way of telling if the result is correctly positioned - typically smallish offsets to one or more of X,Y,Z can occur and these are not obvious if there is nothing to compare. The ground distances between identifiable points may be very good (to within 2-3 cm. or better) but the whole can be offset by an arbitrary set of values. Some ground control will identify this.

Most professional survey would be done on a pre-programmed routing - RTK simply complicates this by adding the risk of losing the radio signal from time to time, especially during the end of line turns.

Interestingly, a significant part of the data variations come from how the image processing software handles the relative weighting of the camera positions and the ground points. Sometimes it seems that the camera positions take priority over the ground points, rather than the other way around. This is where my attention is now being directed.

On your full size work, what spacing for the ground control are you using? Most of the control we put in for manned aircraft is for linear surveys where we put down pairs or triples every 3km. or so, sometimes a bit further apart depending on the job and flight height.

chris mills, post: 389080, member: 6244 wrote: Shelby,

On your full size work, what spacing for the ground control are you using? Most of the control we put in for manned aircraft is for linear surveys where we put down pairs or triples every 3km. or so, sometimes a bit further apart depending on the job and flight height.

Really varies a lot, most projects are NOT long liner features, scale of imagery and accuarcy requirements determine placement and number of GCP's primarily.

On the subject of positioning, unless you simply need the flight lines positioned more accurately during acquisition (and you might being closer to the surface being mapped), we find PPK allows the same or better accuracy as RTK without the problem of maintaining comms during a flight and of course with a UAS extra power and less sensor payload ability. We actually position the aircraft trajectory a good percentage of the time using Precise Point Positioning (PPP) if project specifications allow. With some ground control it works well and for certain LiDAR applications in forest land we are using PPP quite regularly with very good results.

SHG

I've been testing drone aerial surveys for past 4 months. I have found the GCP (ground control points) are essential to accuracy, no matter if you use an RTK drone or not. Also a high photo overlap of 75% front and side is very important. I see best results with flights at 200ft above ground level. Also seeing that taking photos at 70å¡ angle from the horizon is better for structures with overhands. At this point I don't see any advantage of purchasing a $30k drone w/ 38MP camera versus a $2k drone w/ 12Mp camera. It is the sensor that is most important. I have compared 100's of survey grade measurements from EDM and RTK versus drone point cloud data, and find they are å±0.1ft horizontal and vertical about 90% of the time. My last project I thought there was a problem at one of the ground control points, as the vertical difference was 6.7ft. Then I realized I had occupied that point during the drone mission with my RTK base using a rod height of 6.56. The point measured the elevation on the top of my GPS receiver, not at ground level. The receiver is a Topcon Hiper V, just a 5" round foot-print visible from overhead. Vegetation is still a problem. The point cloud measure to the top grass and leaves. I'm wondering how lidar get's through the vegetation?

Here's a good article on LiDAR vs Photogrammetry
http://www.spar3d.com/news/lidar/drone-lidar-vs-photogrammetry-technical-guide/

leegreen, post: 389152, member: 2332 wrote: I'm wondering how lidar get's through the vegetation?

Magic! Actually if totally solid it isn't going to, BUT with the million dollar sensors anyway, you get multiple returns and last return is assumed to be bare earth, actually works pretty good at getting at least some return back that is actually on the ground, BUT of course if the laser can't see the ground at all it won't. Somebody way smarter than me figured this all out, but LiDAR in vegetation does work pretty good to get the ground most of the time.

SHG

Just googled this drone size Lidar sensor PUCK䋢 (VLP-16). They show test results using this with a DJI S1000 drone. Looks like Leica also has several UAV's with lidar, which are probably priced over the $30k range.

I have to contact the UAS instructor at our college, MVCC where Duane Frymire PLS and Alan Chase PLS are assicatiaed (both of which are now or formerly on this board). They have invested over $350k in drones, not sure if they have Lidar scanner system.

Velodyne's new PUCK‰ã¢ (VLP-16) sensor is the smallest, newest, and most advanced product in Velodyne's 3D LiDAR product range. Vastly more cost-effective than similarly priced sensors, and developed with mass production in mind, it retains the key features of Velodyne's breakthroughs in LiDAR: Real-time, 360å¡, 3D distance and calibrated reflectivity measurements.
KEY
FEATURES

• $7999
• Dual Returns
• 830 grams
• 16 Channels
• 100m Range
• 300,000 Points per Second
• 360å¡ Horizontal FOV
• å± 15å¡ Vertical FOV
• Low Power Consumption