Anyone using a Sparkfun or ArduSimple RTK GPS?

AMann · Sep 21, 2023

For less than $600, both of these RTK systems look pretty good for plotting in GCP’s. Anyone using these? Looking for recommendations or cautions. I’m leaning towards Sparkfun’s Survey Kit at $575 due to the upgradability to using it as a Rover or Base if I ever buy a second one, but the ArduSimple is less than $500 as well…

This would be for basic educational use with a tight budget, not for demanding commercial use.

Thanks!

Airmapper · Sep 22, 2023

No, but now I want one!

I have a pair of Spectra SP-80's at work, but that should be more than adequate for GCP points. Might be a bit of a hassle to get all the software kinks worked out, but then again, did I mention I use an SP-80....

AMann · Sep 22, 2023

Airmapper said:
No, but now I want one!

I have a pair of Spectra SP-80's at work, but that should be more than adequate for GCP points. Might be a bit of a hassle to get all the software kinks worked out, but then again, did I mention I use an SP-80....

I’m going to go ahead and get a pair of the $575 Sparkfun Survey Kits, and use the second one for a base station. I’ll post a review about them after I check them out.

Arnold LeVine · Sep 23, 2023

Anxiously awaiting your review!

AMann · Sep 23, 2023

Arnold LeVine said:
Anxiously awaiting your review!

First I have to get a school PO approved (they will) and education account from the store…

Airmapper · Sep 27, 2023

I'm sure there is a way, but what I'd love to know about these is how to collect a static observation file in a Rinex format for OPUS translation. I'm assuming there is some way you can log the data but so far I haven't seen any documentation describing how you would go about it.

I'm very tempted by that Ardusimple unit. That handheld rig won't cut it though, I'd need the antenna on a fixed height pole if I wanted to do any data collection of any seriousness. I'm sure I could build one though.

AMann · Sep 27, 2023

Airmapper said:
I'm sure there is a way, but what I'd love to know about these is how to collect a static observation file in a Rinex format for OPUS translation. I'm assuming there is some way you can log the data but so far I haven't seen any documentation describing how you would go about it.

I'm very tempted by that Ardusimple unit. That handheld rig won't cut it though, I'd need the antenna on a fixed height pole if I wanted to do any data collection of any seriousness. I'm sure I could build one though.

You have a very good point, and I would interested in being able to do post-processing as well, so collecting raw Rinex data would be important. That’s another thing one should be sure of prior to purchasing one.

AMann · Oct 2, 2023

I just picked up two Sparkfun RTK surveyors along with a pair of external serial data radios and GPS antennas for them. I am planning on using them as a rover and a base. At $1300 total for everything it was a pretty inexpensive investment to get sub centimeter RTK accuracy. Both units are small and only have two switches on them - one is for power on/off and toggling the other one changes functions between rover and base modes.

They are not waterproof and are lightweight, so care will be needed if there is any rain or blowing dirt. They seem to be well made though, and the Bluetooth function (BLE mode for iPhones) works well. Field testing with the SW Maps app will start soon…

AMann · Oct 3, 2023

Update. The Sparkfun RTK Surveyors I got work well. I had to update the firmware in order to get the BLE Bluetooth function for my iPhone and iPad. SWMaps app looks very good for working with these units in RTK mode, and I was getting a horizontal accuracy of 14mm in RTK mode!

Very happy with these units and price is great. Besides using it to survey in GCP’s for making better quality aerial orthophotos, I’m also going to be using it for plotting features on a volunteer archaeological project I am doing at a National Park, and I’m planning someday on getting a third one to use on a Pixhawk controlled drone to turn it into a RTK enabled one.

AMann · Oct 4, 2023

I went out today to try it out with SWMaps. I tested it out by taking points along a 100-meter long tape. The system works really well and was very precise as the distances it recorded between each point along the tape were dead on within ~10mm. I was using the moving base method so the precision was very tight between the different points I made, but as it was a temporary base, I need to learn more about using the fixed base method. That will make the readings more accurate as the entire line was uniformly shifted north about 14-feet from where the tape actually was as a result of using a temporary base that was not set on top of a known point.

Airmapper · Oct 5, 2023

Very cool. Sounds like you did what I call an Autonomous setup? I'm not familiar with the moving base terminology. It could be corrected with a static observation I bet.

I'm surprised it's 14ft off if it's RTK though. I thought that was almost as good as a base on a known point.

AMann · Oct 6, 2023

Airmapper said:
Very cool. Sounds like you did what I call an Autonomous setup? I'm not familiar with the moving base terminology. It could be corrected with a static observation I bet.

I'm surprised it's 14ft off if it's RTK though. I thought that was almost as good as a base on a known point.

14-feet of error for a non-corrected base plot is to be expected and would be that bad even with a expensive professional grade GPS system.
RTK has two modes- “moving base” is when you don’t set the base on a known point- it has no way to know exactly where it is as there is no correction for it- but it will still allow the rover to give a very accurate measurement of the distance it is from the base, so it’s a relative measurement. To get an accurate RTK correction reading from the base relative to where it actually was placed on the ground, you have to place it on a pre-surveyed point (like a benchmark) and enter the coordinates from where it was placed. The base will then add the difference between what it measures and the actual coordinate value to the corrections it sends to the Rover. If you are using a paid RTK service, their base has already been put on a established location so the fixed base RTK is a very accurate measurement overall.

Airmapper · Oct 6, 2023

Ohh I see. I thought you were getting NTRIP RTK to the base is why I thought 14 ft was terrible. Yes that is the same method I use with the Spectra.

Here in KY access to the NTRIP is free, you just need an account with the Dept of Transportation which I have but have yet to take full advantage of.

AMann · Oct 6, 2023

Airmapper said:
Ohh I see. I thought you were getting NTRIP RTK to the base is why I thought 14 ft was terrible. Yes that is the same method I use with the Spectra.

Here in KY access to the NTRIP is free, you just need an account with the Dept of Transportation which I have but have yet to take full advantage of.

No free NTRIP here, plus I’m cheap and want the students to learn more so we just plug in base coordinates we get from Google Earth for a ground feature we can easily see on campus. It’s not exact, but it does demonstrate the concept to students. They are responsible for finding the coordinates and working with them, placing and shooting in the GCP’s and planning their flight when we are learning about aerial mapping.

ELB DRONEZ · Oct 21, 2023

I’ve been going in circles trying to understand the actual use of these systems. I like the Spark system. Does this eliminate the need for a RTK module on the actual drone???

AMann · Oct 21, 2023

ELB DRONEZ said:
I’ve been going in circles trying to understand the actual use of these systems. I like the Spark system. Does this eliminate the need for a RTK module on the actual drone???

This all depends on the type of project you’re working on.

For the most accurate and most time-consuming project, you use a RTK enabled Drone along with ground control points (GCP’s) that are really just any type of marker you stake to the ground that you can see later on the aerial photos you take. Most surveyors use a large + plus sign pattern with a steel nail or other immovable point in the middle. You then have to get accurate positions of the middle points of all of the GCP’s using a survey grade GPS. This gives you accurate location points to use in your photos to create very accurate Georeferenced orthophotos.

You do not have to use RTK on a drone if you use enough GCP’s to show up in all or most of the photos you take, however, it requires a lot of work to get all those GCP’s, so it’s time consuming. Currently I can only use this method as I just have a MP2, but my projects are small (less than 10 or so acres) so it is relatively easy for me to cover it using GCP’s.

If you’re using an RTK drone, you need a base station also for the drone and you can shoot without GCP‘s, and the final product won’t be as accurate as when using both methods together, but it’s a much faster way of covering large areas with good quality accuracy. One problem with this method is if your drone doesn’t get a good GPS location and fails to pinpoint the center of any of the photos, then you are relying on your processing software to be able to edge match it to the others. It’s a good practice to use at at least enough GCP’s to cover the project corners and a few center points for any mapping project.

AMann · Nov 18, 2023

Update - the Sparkfun RTK Surveyor works very well - I bought 2 and use one as a base station. They are currently on sale for about $350 each this week.