Big uas mapping gcp and terrainPosted by tonyduky on September 5, 2022 at 7:13 pm
Currently prepping for a 70km2 mapping project kn the middle east. Probably all PPK + 4 gcps per km2.
Terrain has a lot of elevation changes (valleys) so i m gonna have to set up multiple base stations. (No cell coverage so no ntrip). Im wondering if there is any radio coverage simulation software for google earth to anticipate where i should preferably setup my base stations.
Ill be working with a trimble R2 mobile and a trimble R8S base with TDL450 radio with a big antenna.
Thx a lot for your help guys!
- 19 Replies
- MemberSeptember 5, 2022 at 7:30 pm
What about using PPK with satellite based Trimble CenterPoint RTX (~2cm)?
- MemberSeptember 5, 2022 at 8:38 pm
I’m not sure why you’re talking about radio coverage for PPK, since PPK by definition does not incorporate a real-time correction signal. Maybe you meant to say RTK?
FYI, RTX convergence is faster than typical PPK convergence, almost immediate in many areas, but at worst maybe 5 minutes. There’s no need to wait for an hour at each target.
If you are in fact looking to do RTK and not PPK, I don’t know of any app that would easily calculate your base station positions.
But 70 km2 is not super large (assuming it’s more or less a rectangle), only ~8km on a side.
Personally, I would set up the base station to broadcast with the internal radio at a high point that is central to the project, and boost it up high with the long cable and whip antenna.
Then I would drive around with the TDL running as a repeater inside of the vehicle, and the standard omnidirectional antenna on a magnetic mount on top of the vehicle.
That way you can park at the top of a peak or ridgeline, make sure the repeater is picking up the base corrections signal, then hop out to set targets. If you need to walk down in the valley to set a target, just make sure you can maintain line-of-sight with the vehicle and you should get radio for ~95% of the project without ever moving the base.
I’ve done this on quite a few projects that were larger than 70 km2.“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman
- MemberSeptember 5, 2022 at 9:17 pm
You will waste far more time setting up the base, driving to a new potential base location, setting a new base, shooting a new base, driving back to the original base, tearing down the base, moving, setting back up, rinse repeat.
If you’re worried about “time”, then your best bet is a variation on @Rover83 ‘s suggestion where you ditch 2 way communication altogether.
Set a single base in the center of the project and do rapid static “around the wheel” in a pinwheel type shape. If you were going to do PPK anyway, then obviously you know how to post-process.
Two sessions (7 minutes, then 3 minute sessions (check), or one 10 minute session per GCP would probably give you appropriate precision/accuracy.
My original proposed method would give you a real time solution, plus a PPK check from the central reference station all in less than the time it would take for base/rover leapfrogging.
You didn’t mention where in the Middle East you were working, and you didn’t say if you planned on taking your US gear with you, but hopefully you are aware that there are differing levels of sanctions and some export restrictions for certain US technology to various countries, etc.?
- MemberSeptember 5, 2022 at 10:28 pm
@rover83 yeah the uas will probably fly on PPK (uas operator will have his own emlid gnss setup) but i would like to set the targets with RTK if possible so we can save time.
Love your idea about the radio setup but i have a few questions :
– how far can you boost the internal radio signal of the r8s with the big whip?
– what kind of magnetic mount you re using for the car? Do you leave it on while driving? Probably gonna be rough offroad driving…
– we will have two 12 volt 12 amp powersonic lead batteries (one for the base and one for the TDL450). How do you setup the r8s to run on the lead battery instead of the small li-on internal battery?
What kind of cable do you use to connect the lead battery to the TDL?
For now i v been using the standard Y trimble cable that connects the external battery to the base and the radio at the same time. Can i use two Y cables to power up the TDL and the r8s separetly? (Buying a spare Y cable might be more useful later than another cable type)
– about rtx last time i used it in KSA i couldnt reach 2cm accuracy even after a 2 hours static…
Sorry for the rookie questions, im more of an archaeologist than a surveyor…
Thanks a lot for your help guys!
- MemberSeptember 5, 2022 at 10:29 pm
- MemberSeptember 6, 2022 at 5:58 am
I second Rover83 and raise him by using the base radio as the transmitter and take a planning session to see where you can set the TDL450 as a repeater,
and do Rtk and logging so if and when you lose the Rtk you can take static shots and resolve the base data and spend less time with less setups. baselines won’t be very long and there’s not lots of trees to ruin the horizon depending on where you’re working.
You need a Y-cable for the R8 to run off of the 12Volt set up and it’s a simple set up. Same for the TDL450
And maybe consider having a Solar panel at the TDL450 to keep it full up charged so you can leave it in the best location unless there’s a risk of theft, but not imagining that’s an issue.
- MemberSeptember 6, 2022 at 8:24 amPosted by: @tonyduky
– how far can you boost the internal radio signal of the r8s with the big whip?
Even a relatively small increase in the height of the aerial makes a huge difference to the “line of wave sight”. Depending on terrain you might get an extra km. or more. I found this out early on and made adaptor brackets which take the Trimble aerial up the side of the receiver so aerial is 150mm above head rather than 150mm below head. I also made 1 metre lightweight extension rods to screw into the socket, so that base aerial height could be lifted by 1 or 2 metres.
If you are doing fast static then they can also be used on the roving set (but you can’t walk around with 2 metres of rod cantilevered off the receiver, so its a static on tripod or bipod). Same effect achieved with a whip aerial, but at the time I needed a same-day solution. The little brackets are always used – saves those annoying situations when the radio signal drops 10 metres from where you want to be.
- MemberSeptember 6, 2022 at 10:08 am
So If I understand correctly I will need :
– a 12 volt car battery to power up the R8S for a long time (solar panels are not an option, mission starts soon).
– a cable for connecting the car battery to the R8S : https://www.amazon.com/SZRMCC-Battery-Alligator-Trimble-Station/dp/B07ZQCT6ND
– an antenna magnetic mount for the car connected to the TDL450 : https://www.amazon.com/gp/product/B083GJ8V3L/ref=ox_sc_act_title_1?smid=A53D4KYDMI7UZ&psc=1would this be compatible with TDL450?
– a Y cable for connecting the lead battery to the TDL450 in the car : https://www.amazon.com/Trimble-Receiver-Pacific-PDL450-RFM96W/dp/B07YDDY4WH/ref=sr_1_2?crid=BXPS8U8KT089&keywords=cable+Y+trimble&qid=1662460059&sprefix=cable+y+trimbl%2Caps%2C202&sr=8-2
Does everything seems right to you guys?
Thanks a lot!
- MemberSeptember 6, 2022 at 11:46 am
this is the best place to get the cables for your project, and they’ll be better able to get you set up.
understood on the solar, this is the mount you need
just use the Trimble or WSC gear, that Amazon garbage will leave you stranded in the desert.
- MemberSeptember 6, 2022 at 11:47 am
Have you confirmed that you will be allowed to use a radio. And if so at what power and frequency. Some places do not allow the use and in some places you would not want to for safety reasons. I assume this part has been checked into already. There use to be some software you could take some topo maps and create a surface and do line of site studies based on telemetry locations and radio what power. Or you could probably do it with esri software as well.
- MemberSeptember 6, 2022 at 1:41 pm
You have an R8 base with a TDL450 repeater radio, they can be miles apart and it will surprise you how far from line of sight the repeater radio will pick up the base compared to the rover.
Friday I was over a huge ridge heading down into a valley and needed to get signal with the rover but it wasn’t picking up the base, I had the repeater knowing it would be needed and was able to get the base far over the ridge into the valley no problem, I set it up 4 ft high and did the valley survey.
My suggestion is to carry it along with you, don’t worry about line of sight, see where it will pick up signal and use it as the repeater. If the 70km2 is a square area one base near the middle on a high point should get everything with the TDL450 moving around.
For PPK, if you’re using a Trimble DC in survey styles I set the time to fix at 3 minutes for 4 SVs, 2 minutes for more. It defaults to some long times that simply aren’t reasonable.
The key to PPK is to organize the sessions (not the location times), if you’re going to use it begin the PPK session before setting out the point or laying down the target. When you have the point set and targeted the PPK session should be fixed and ready to go, the rover can be leaning against the truck or sitting on a mount on top as it fixes. Then put the rover over the point and collect. The default will be 3 epochs or 15 seconds if your base/rover collection times are set to 5 seconds which is how I would do this job. I would advise at least 45 seconds and for something like this 2 minutes is a good number. I’ve never had a failure for a base-rover PPK with 3 minutes fixed and 2 minutes collection. You will need to check in the software what a minimum time is for PP and turn it down if your sessions are shorter.
A PPK session can run all day if you have your rover mounted outside as you move around, the longer the session the smoother it will all work.
As always more than one location per point is needed.
This is all based on my experience with trimble receivers from the 4400, 4700, 4800, 5700, R8, R10s, they all worked the same way with PPK, however, I’ve never used an R2.
RTKInfill is a Trimble style that merges the two, if you want to use that style it may be a bit confusing, but it works well. I’ve not been a huge fan but for this project it should be a good option. Just work through all the styles and set init times and collection times to reasonable numbers. Then you can collect RTK when you have radio and go to PPK when you don’t.
- MemberSeptember 6, 2022 at 3:45 pm
A job this size is not really a uas type of job. I would call my local mapping company and they would fly it for 1/10th the cost and twice as fast.
It that not available where you are?
- MemberSeptember 23, 2022 at 9:29 pm
Another option besides fighting a radio is set up an air-link raven modem at the base you can configure it with a static ip and port address. Then use a cell phone or wifi at rover end. Just like a server if you have cell coverage you can go further than the r8 will be able to resolve the interger. Anyway. You could post the ip and port here and we could connect in the states just never would fix is all. You could do this with the old tsc2 and survey controller software pre Trimble access. Make the base act like a single base network is all.
- MemberOctober 6, 2022 at 3:21 pmPosted by: @tonyduky
Regarding the points I’m taking far away from the base, what acquisition time should I set up for the mobile rover?
I think it’s set to 5s now but I’m wondering if it should be longer?
That depends on whether you’re running RTK or PPK, and also what the required precision of your observations are. Generally for PPK I’ll bump up the observation times, often doubling them, in order to ensure post processing will yield solid values.
I’ve worked projects where GCPs had to be down to the 1-3cm level vertically, and others where it was half a meter.“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman
- MemberOctober 6, 2022 at 10:11 pm
- @rover83 accuracy as to be from 1 to 3 cm as its a quiet precise uas survey. I’m using RTK. Would you recommend a longer recording time than 5 s per point?
- A colleague can bring another rover to help me. Its a Satlab SL600. I was wondering if we could connect it to the R8S base using the uhf radio as well so we could work with 1 base, 1 repeater and 2 mobile rovers at the same time. Pretty sure i wont be able to use trimtalk protocol anymore if i do that?
Thx a lot for your help.
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