Do you think if I mount the GNSS Multi-Band L1/L2 Surveying Antenna - TNC (TOP106) to a mast attached to the bulldozer blade, that the vibrations could destroy the antenna?
If so, can you guys recommend a Surveying Antenna suitable for bulldozer blade mounting I can use with the SparkFun RTK kits?
I suppose I won’t know until I try it, and I could just buy some extra antennas since they are so cheap anyway. I would imagine the “ruggedized” ones are much more expensive.
As a matter of curiosity why not mount it to the top of the cabin?
Because @jeffersonkim is referring to what the construction industry calls “Machine Grade Control”.
The purpose is to be able to know where the dozer blade is in reference to the Proposed Grading Plan.
The Operator will know how much cut/fill any area requires based on the location of the blade’s cutting surface (vertical is the most important).
Machine (Grade) Control has experienced a huge amount of growth in the past decade.
I believe it followed the Agricultural Industry that got it’s start in AutoSteer.
The Open Source community is supported by AgOpenGPS and projects like OpenGrade3D.
@jeffersonkim , I wouldn’t be afraid of using TOP106 antennas for a rough grading application. It’s a good design and a great value.
For Finished Grading, the construction industry typically adds Total Station/Laser tech to reach a final bluetop accuracy of ~1mm, when required by the project.
Vertical lines are spaced 7.5’ apart along a 52’ span between the red lines to maximize the 9’ blade. I edited the KML files manually referencing an online calculator and excel spreadsheet for correct spacing.
Each of the horizontal lines are spaced 50’ apart to match engineered drawings that specify altitudes along the center of the finished road.
The theory is that combined with Caterpillar’s AutoAssist features built into their D3 dozer (can set incline/decline & cross slope of blade relative to the vehicle), along with 1/2" altitude accuracy of the GPS blade, this should be sufficient for this project.
It’s just a 1/2 mile straight road.
This is a pretty fascinating topic. Thanks for the in depth explanation.
In general GPS antennas are not very fragile. But for very precise vertical positioning a second for.m of sensor is used in general.
I’m pretty sure the OP @jeffersonkim already knows this, but it’s an interesting topic and I’d like to mention the next step for others in the future.
The user will usually perform a Localization or Site Calibration. The Engineered drawings are typically in a local system, NAD83 State Plane Coordinates for example. On such a small site, the Grid Coordinates wont pose much of an issue, but the elevations will. You basically need to identify the Elevation difference from your GNSS observed points verses the existing elevations on the plans. Depending on the Vertical Datums used, this could be a difference of several feet. Once you localize to the site, it wont matter, as you will apply that difference to all your proposed points (you shift your proposed surface to match the local system, even if it’s an arbitrary system).
I’ll admit that I’ve oversimplified this, but localization allows you to Stake-Out points straight from your GNSS.
Thank you. I’m new to this, so I did not know. Will using an NTRIP provider or Spark Fun RTK Reference Station help improve the vertical accuracy?
It appears on SW Maps, that I’m getting about 8" vertical accuracy with the SparkFun RTK Express out of the box simply in Rover mode without any additional correction data.
(I went ahead and ordered a RTK Reference Station & will set it up at the construction site. The antenna will be within 50 feet height of the road altitude, and within 1/2 a mile.)
Be sure to check out the RELPOSNED message on the ZED-F9P. RELative POSition North East Down, gives you the relative position of the Rover compared to its Base. In a “Moving Base” scenario, this can provide excellent relative positioning, but not absolute. For absolute accuracy, the moving base needs its own corrections, from a local fixed base.
Another user was trying to do (almost) the same thing here. Their application was drone orientation, compared to a moving vehicle. But the principles are the same.
Hope this helps,
Paul
Operating your own Base at the project site will provide the best results, by far.
The Rule of Thumb that’s always quoted for RTK is 1cm + 1ppm.
That’s saying, that under the absolute best test conditions (and very expensive antennas), the RTK relative accuracy is 1cm + 1 cm for every 10km (6 miles) of baseline (distance between base and rover).
Generally speaking, I wouldn’t put any confidence in the GPS Uncertainty (Perceived Accuracy) values reported by any GNSS device. The device would need to know it’s actual location to be able to provide any meaningful data.
There are several ways to accomplish what you want to do.
I think the easiest (if you don’t have Surveying Software and Data Collector for coordinate transformation on-the-fly ) would be to setup your semi-permanent base for the project and get it’s position sorted out, just like normal. Then locate/store the positions of various site features on the construction plans with your Rover, especially any control points. In your MS Excel Spreadsheet, you will define the N,E,Z offsets for each pair of positions for your Site Calibration (Published - Located) and establish a best-fit offset. Then have MS Excel create a new list of proposed stakeout points that have been adjusted using the “best fit” offset value for N,E,Z across the entire project. Now your points have been Localized to the site so your SparkFun RTK Rover positions can be used easily and directly.
It’s basically similar to opening the design in AutoCAD and moving the project site to ITRF, which is the reference frame of your RTK combo.
Great ideas! Thanks.
I just wanted to provide an update.
I just set up rtk2go as the caster and now sending out coordinates.
Since the final road height will need to match the public road, I can actually use the public road as my “monument” and then reference the rest of the road to that since I already have markings for finish grade.
We also mounted, using a piece of wood as an “adapter” of the antennas to the dozer blade. Excited to see this work!
I love it !
You might be the first person to bring SparkFun RTK into the Machine Grade Control Industry?
As you already know, Machine Control is generally terribly expensive.
I would love to see a picture of the road profile when you get it graded 
Did you go with a single mast at the center of the blade?
Yes. Single mast in the middle.
Well, it’s my own road, so I’m not trying to impress anyone. But if I were a contractor, it may look a little sketch to clients, especially the larger entities that have deadlines.
Likely you’d see more contractors in my area using it if they had reliable tech support on-site. If you added in the cost of hiring a tech-hand to set everything up, I’d imagine paying $100k for a Trimble doesn’t seem so unreasonable, as I believe the Trimble/Cat partnership would provide ongoing support.
The wider appeal use case likely is with the farmers in my area. But I won’t be able to do that until I actually work in the field and work out the kinks.
Also to clarify, it’s not machine controlled. I’m just going to have SW Maps open in the Dozer so we can see the altitude of the blade. Hopefully the built-in latest gen auto-assists will be enough.
I’ll keep this post updated as I work out the kinks, and maybe one day do a YouTube video.
During a shower, I was contemplating the annoyance of having to adjust my lines to accommodate the fact that the antenna is only in the center. Then I realized that there are locations for 3 masts on the blade.
This means that if I attach a $250 or so mast onto each of the three locations, (left, right, center), then I can simply reattach the antenna to each of the masts depending on which side of the road I need tracking.
I’m using this clamp along with the standard 5/8" bolt from Home Depot for a really cheap “mounting” option that makes it easy to switch between the masts as needed.
It’s still to be seen how these handles hold up with the movements of the blade, and I may need ot look at some stronger clamping actions.
The other benefit of having an adjustable clamp is that I can have the antenna really sticking out toward the edge of the blade and at various angles depending on the task.
Also, I discovered that there are $100 5G Tablets that I just ordered with T-Mobile $10/month data-only cards. To be mounted in the dozer with this tablet holder. https://www.amazon.com/dp/B0936P1MNB
The one annoying thing we discovered is that when you lose data on the phone from switching to Wi-Fi to 5G, it also loses NTRIP connection, and you have to reconnect.
Another idea is that if I really want to permanently attach the antennas to the masts, I can have 3 different antennas on each of the masts, and then use something like this antenna switcher for the operator to switch between different antennas.
ANT 1 = Left Mast
ANT 2 = Center Mast
ANT 3 = Right Mast
I will post separately for this idea.
