PPK of a single point having a Base on a known point

Hello and thank you for reading.

I am a total newbie to this world and I have been learning, slowly but firmly. I would say, one step at a time using this forum. So many motivational and good people around here.
In spite of this, there is a lot of information available that I have difficulty grasping or understanding, and combine that with my lack of CIvil or Surveyor Educational backgrounds either, that’s why I just decided to ask about the topic I am in need to learn and I lack knowledge, PPK.

I have read the Emlid Guide for PPK as well as some threads in the forum but I can’t seem to find the answer that I am looking for. I somewhat figure the process of PPK out. Obtain observations from base and rover and the navigation file from either one and post-process them using a dedicated PPK software.

Can someone point me to a thread that shows how to PPK a single point in “static” mode having the base on a known point and find the coordinate of my static rover? Or perhaps show me how can I accomplish this?

I have the Emlid Studio and RTKLib software Even though I like Emlid Studio for its simplicity, I am not sure if Emlid Studio can give me the coordinate I am looking for.

Many of the threads that refer to PPK combine drones to this process or relate to “kinematic” PPK, but I can’t find a thread that can show a basic “static” PPK of a single point without the use of an active station, I forgot to mention this before.

One more thing I forgot to mention was that I have 2 RS+'s. Not sure if this changes things.

I am very interested in how this GNSS science works. For now, I just want to be proficient in the basics so I can continue learning. Thank you all for the great support I have had so far.

These are two services you can use for PPP (precise point positioning) if you are out in the middle of nowhere and have no local known passive control marks and no CORS available. You’ll need long observation times (minimum of 3 hours), especially with a single frequency receiver. There are excellent explanations on both sites above explaining the methodology.

If you have your base on a known passive control mark and you are using the rover with LoRa (RTK), you’ll have the coordinates of the rover if the known coordinates are entered correctly in base receiver.

If you are just doing a static observation for both the points, it’s a simple matter of post processing the rover using the base with it’s known coordinates.

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Thank you for replying Bryan, I will have a look at the PPP services you mentioned. I read a little about PPP, and what you say confirms what I have read. PPP will be my next subject to learn. It seems very useful since where I live, is limited to a few control marks and active stations far away, the closest is 200+ km.

How do I find the coordinate of the Rs that was not on the mark? I used Emlid Studio and PPK on “static” mode and generated the pos file but I am stuck. don’t know what to do with it. I opened it in notepad but It only shows the control mark coordinate. Am I doing something wrong?

While I ran the process of PPK, the software showed Single+Float+Fix+Single. Does this mean that the Base and Rover connected each other over LoRa? I mention this because the control mark is on the outskirts of the city and the point I am trying to post-process is incrusted in the city around 2.6 km separated. Seems weird since on one occasion I ran the base and rover on this specific control mark and test the distance that both Rs’s maintained Fixed status. the result was roughly 200 m of constant connection in between.

Anyway, keeping to my question. Considering that I did not make mistakes on my PPK, how do I find the other coordinate after generating the pos file?

Sergio, I’m not understanding your situation ? I thought you said the base was on a known control mark ?

If that’s the case it’s a simple matter of using the base with the known coordinates and post processing the rover with the base. Single frequency receivers must have a clear unobstructed view of the sky in order to get an accurate real time (RTK) or post processed solution. Also, observation times for single frequency receivers are a little longer than dual frequency like the RS2 or M2’S.

Are you using the LoRa radios for RTK ? The Emlid radios are good radios but must have a clear unobstructed pathway for the radio signals to reach the rover from the base. I’ve experimented with mine and on level topography, I’ve gotten about 2 km range on the radios through large wooded areas, although this was really pushing the limits in my situation. It also would increase the range if your base and LoRa radio was on a higher point than the surrounding areas.

Is this what you are talking about ?

Thanks for replying again Bryan, I think I mixed 2 subjects in one thread, my apologies.

Yes indeed, my base was on a known point but no LoRa connection to the Rover.

My goal is to find the coordinate of the rover related to the base on top of the control mark so I can set up an Emlid NTRIP caster base in my home, which I have an idea of what it can do, however, I need to dive into it more first but not until I understand better the PPK process.

I am guessing that I did something wrong with my PPK workflow, now.

My PPK process was to set the rover on a tripod on top of my house, then I went to the known mark and set up another tripod with the base. The rover and base recorded information together for about 30 minutes, more or less, and turned them off. Then I downloaded the needed files and worked on the PC.

I am guessing my mistake was that I just simply ran the receivers and let them capture information but I didn’t save or captured any points in RV3 at all. Should I have saved the coordinate of my rover after I set it up?

No, not if you’re just doing static observations. You can but without LoRa (RTK) or any kind of RTN access or without PP you’ll just have meter accuracy.

I don’t know where you’re located but if you’re doing a lot of work with your RS+'s, you might want to consider a RTN subscription if available in your area. You’ll need good cell coverage also for the RTN to work.

I’ve been subscribed to our state (SC) RTN for about 6 years now and it’s paid for itself many times over. It reduces the hassle of setting up a base on projects, not to mention the associated worry about leaving the base unattended.

I’ve got two M2’s and I use them as a static baseline for project areas where cell coverage is minimal. I use my Javad Victor LS T2 as my rover using the RTN. When I loose cell coverage, I can keep on keeping on with the rover performing static observations and then PP the static observations with the M2’s. That way I’ve got a static triangle observation for each point located without cell coverage for the RTN. Usually the baselines are less than 2km. I’ve learned down through the years that short baselines are your friend and you’ll obtain higher accuracies with shorter static observation times.

Many of the the loop closures for the static triangles have closures exceeding 1: 300,000, usually around 1-2cm both horizontal and vertical for each point. I use commercial post processing software, however I’ve used RTKLIB in the past but it only processes single baselines. I’d like to try using RTKLIB again, but my main concern is getting the work out.

Just keep trying on the post processing, there’s all kind of information available here in RTKLIB settings as well as other members that will help you. I think it’s fascinating post processing static observations.

One way to learn without any fieldwork is to post process CORS data by holding one station as fixed and using other surrounding stations for your observations. That way you’ll have a check on your processes. Another way is to use two passive control marks and hold one as “fixed” (your base) and compare your resulting “rover” point with the actual control coordinates. Try and keep your baselines as short as possible too. Single frequency receivers need “clean” data (open sky conditions) and don’t have the range capabilities of dual frequency receivers.

Have fun !

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The more I see here, the more interested I get in GNSS. Thank you for your advice Bryan, I see that you contribute quite a lot to this forum.

I am from overseas. I live in a country in development. This means that there aren’t many government RTN stations on range. The closest one is 200+ km away. No NTRIP services, although there is a CORS Station nearby. My problem with this station is that I can’t afford it at the moment, I will have to put that on hold for now. One more thing, the cellular network around here it’s not the greatest either.

The main reason I want to set an absolute coordinate on the top of my roof is, so I can set up to try and work with the Emlid caster service, it’s free, isn’t it? Would this be a good solution if I want to do RTK close by?

Note: I have no surveyor background, I am learning as I go. At this moment I am in the basics of GNSS.
I have not been able to find the coordinate on my rooftop using PPK, yet haha. Still not sure what I am doing wrong, I will keep looking here, thanks for your advice, Bryan. I wish someday I can be as professional as you and thanks again for sharing your invaluable knowledge.

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Thanks Sergio ! There’s others here that are more knowledgeable than me. When our firm purchased our first Trimble receivers in 1988, my dad handed all the manuals and software and said “figure it out”. I went to two customer seminars and was completely lost. It was a ten day event and there was 3 manuals on the receivers and 4 for the software. After fumbling around with all the manuals, software and receivers it finally sank in. I’ve been learning ever since on various receiver models and PP software.

Use the PPP service for your roof top station. If it’s
a stable mount and the receiver will be a semi permanent mount , perform an 8 hour observation (minimum) and submit to CSRS-PPP service. If the station is permanent, just enter your ARP as “0” and select the proper receiver and/or antenna. This will give you the computed station at the ARP. If it’s a temporary station on the roof, also make sure you enter the instrument height from your mark on the roof to the base of the antenna or receiver, (antenna reference point, i.e. ARP). The computed position will be for the mark on the roof. In either case, you’ll have your own control mark and be able to reference any future rover points to your base by PP. Emlids’s caster is free. One of these days I’ll find the time to experiment with it myself. They have an excellent tutorial on the caster setup.

Emlid also has an excellent tutorial for the various PPP services and methodology here

https://docs.emlid.com/reachrs/tutorials/post-processing-workflow/ppp-introduction/

If you run into any problems, don’t hesitate to ask ! There is always someone here to help !

Have fun !

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Wow! that might have been so frustrating Bryan. Trying to Comprehend manual after manual packed with information and weird words lol. I am grateful for the internet, that’s for sure. On the contrary, you can’t beat the feeling of learning something the right way and see the fruits of your effort, very soul rewarding. One of the biggest reasons I’ve been liking this “discipline” a lot. As you said before, gives room to keep on learning.

I would like to ask a couple more questions that I just thought about, if I may.

If I set the base on my roof and average its position, this will allow me to create the Emlid caster NTRIP service, right? I know at this moment, that the base won’t have an absolute coordinate at all. However, if I survey probably 2 or 3 passive ground marks using the caster, could I use the collected information to find the absolute position of my base on the roof? Would it be a good practice if I do that?

Another observation. I just read the PPP workflow you highlighted. It says that if I have an RS+ (my case), the best accuracy that I can get will be 30 cm after PPP. Will this be true in all scenarios? Is there a walkaround to reduce this margin of error?

Length of time for the observation will determine accuracy. I’ve read others here using 24 hours and waiting on the final ephemerides (usually 10 days before submitting the data you collected) and you’ll have sub decimeter accuracy or better in both horizontal and vertical. You should do several 24 hour observations (3-5 days) and wait for the final ephemerides and you’ll have probably less than 5cm after averaging. I’d go ahead and get you mark established and just start the receiver running !

Yes you could also just start locating your rover stations with your base running and use the “rapid” ephemerides for submitting the next day to CSRS and you should have a fairly accurate position for the base ( probably less than 0.5m or more).

The neat thing is you can be doing all this at once, observations at the base, observations at the rover stations… if you don’t keep up with all the data in some kind of log book you’ll be pulling your hair out !

Just get started on observing the base and a rover station. I would recommend 1 hour minimum for rover stations more than 1-2 km from the base. Also, either pick a permanent mark or establish good marks for the rover stations. You’ll eventually want to re-observe your stations if you upgrade to a dual frequency or just in case of a mistake. Keep good logs in a notebook for antenna/receiver heights, barometric pressure, weather conditions, sketch, compass, pictures of station location.

Eventually you’ll get confident in what you are doing and looking back you’ll wish you’ve had done all this.
You’ll also want to move up in receivers (dual frequency), post-processing software and even CAD for mapping . As I’ve told others getting started in this profession, contact your local surveyors. Introduce yourself, buy them lunch, find out about local college courses that may help . Maybe expressing you interest in the GNSS world will land you a job that will help you learning all this.

Get started ! The possibilities are unlimited.

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Thank you once more Bryan. I will put everything you mention in practice. I hope I can dominate PPK some day in the future, the same way as you do.

I believe that you have earned a keg beer with all this info. I need to figure out shipping costs to SC now, lol.

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Hi everyone,

You’re really in the deep discussion here! Thanks for keeping up the community spirit :slight_smile:

Sergio, welcome to the world of surveying and on our forum! I just wanted to quickly follow up on this: Emlid Caster allows you to transfer the corrections between your base and your rover. It doesn’t provide you with the corrections per se. Just wanted it out there :wink:

Just as Brian has said, if you have any questions alongside your survey, fire away!