Hello,
I purchased an MDEK1001 (kit) from you, I am following the instructions on how to configure a network with 4 anchors and 4 tags.
However, viewing the tags in the android app, the tags keep moving even when stopped.
What could be happening? Can you help me?
Thank you very much.
How much do they move? How accurately was the system surveyed in?
A small amount of position noise is to be expected. How much will depend a lot on the environment and how accurately the system was set up.
Thank you for your feedback AndyA,
I installed 4 anchors in a room (on the walls), it is approximately 3.11m x 3.27m.
The anchors are 2.30 m high.
I used the automatic positioning of the anchors.
I placed 4 tags approximately 30 cm apart, with a normal update rate of 100ms/10Hz and a stationary update rate of 100ms/10Hz.
When viewing the grid, the tags move a lot between them, even when stopped, they even change position.
I thought I would get an accuracy of at least 10cm between the tags.
Should I use manual positioning when installing the anchors to improve this?
Thanks for your help.
Hi AndyA,
I reconfigured the network with more precision, entering values manually (x,y,z) and obtained very satisfactory tag precision values (± 10cm of error).
Now I need to do the same installation, but outdoors in an area of 47m x 27m.
How many anchors would you suggest for me to get the same accuracy I had in the initial test done in a room?
If I consider the information in the manual that says to install anchors at a distance of 20m to 30m between them, would I get the same accuracy of tag position?
Does the height of the anchors impact the accuracy of the tag position?
If so, what height would you suggest?
Thank you very much for your help.
Hi @DiogoFigueira
there are many things (environment, obstacles and etc) that significantly affects the accuracy. So if you wan you have an accurate system then you need to anchors than is the minimum (for 47x27 the minimum is probably 6).
But keep in mind that for higher accuracy you need to set the positions very precisely which is not easy for that distance.
Cheers
JK
I’m not that familiar with the PANS system so I can’t really comment on the number of anchors for a given accuracy.
I would however say that 1) outdoors will generally give better results than indoors and 2) you never know quite how well it will work in a given location until you try it.
If you only want a 2D solution then putting everything at the same height, including the tags, is generally best.
If you want a 3D solution then vary the anchor heights, this helps resolve the ambiguity of whether you are above or below them. Generally the higher you put them the better the vertical accuracy, however this normally hits practicality issues fairly quickly.
As a general rule, avoid getting the installation to good. It’s not very intuitive but if you put anchors in perfectly straight lines then system accuracy suffers. A little variability in the locations so it’s not a perfect grid helps the final accuracy.
The other general rule is you want the installation to be as accurate as possible. We started out using RTK GPS that was good to ~2cm. Now we do an optical survey that’s +/-2mm.
Hello leapslabs,
So for this area, the best would be the minimum number of anchors (6), right? And not for example 8 or 10, right?
I’m going to use a laser meter to capture the positions, ok?
Thanks for your help.
Hi AndyA,
Can you send me examples of RTK GPS equipment so that I can verify the feasibility of using it in an area (grid) of 47m x 27m?
Does this equipment use an antenna in the center of the area (grid) to capture positions (tags)?
If so, I cannot place an antenna in the center of the area (grid), because the area has to be free of obstacles.
Thanks a lot for the help.
The company I work for is primarily GPS technology based so I used one of our own RTK products. The reason for looking at UWB was to replace the GPS indoors.
Survey grade GPS is expensive but you can get almost as good using something like a pair of Ublox F9 dev kits. You need a radio link between them (from memory the dev kits include a radio) and then set one up in a fixed location with a clear view of the sky. And then you move the other F9s antenna to each of the anchor locations in turn and log their locations.
Once you’ve measured the anchor locations you can remove all the GPS kit. Although if you can keep it set up then you can also use it for verifying tag location accuracy.
@DiogoFigueira
the minimum would be like 6, but you need to test it first.
FYI: Regular laser meter for 27m is very hard to point. Maybe you can use total stations for measurement - but I have limited knowledge here and Im not sure if it is possible to rent them. (they are quite expensive)
Cheers
JK
Hi AndyA,
In case I don’t get the necessary result with MDEK1001, I’ll try to buy the Ublox F9 dev kit.
If you have a place for me to purchase this equipment, please let me know, ok?
Thanks a lot for the help so far.
Hi leapslabs,
It will be really difficult to aim the laser meter to get the exact positions.
But I’ll try and then I’ll tell you how the result was, ok?
Thanks a lot for your help so far.
Renting a total station may not be a great idea. I’m sure you can, but they aren’t the simplest bits of equipment to use.
With the correct software a robotic one that tracks markers can de-skill the task significantly but then you are looking more at an integrated solution rather than just a piece of equipment. I’m not sure if you could rent that.
This is the option we went with, a self leveling robotic system, retro-reflective prisms on all the anchors and software integration into our setup system. We can accurately set up a 12 anchor system in 30 minutes this way using a process that anyone can learn in 15 minutes. It’s saved us huge amounts of time and support issues. But you’re looking at almost $10,000 worth of equipment just to aid setup, clearly not an option for a lot of people.
A better one off option would be to hire a survey firm to come out and do the measurements for you. But that assumes you can keep things in the same location long term so you don’t need to measure things more than once.
If using a laser then put some large targets on the sides of the anchors, being 30 cm to the side at >20m isn’t going to have a significant impact on the distance and lets you aim a little less accurately. Use a tripod to stabilise the pointer, good ones will have a small sight you can look down to aim since the laser dot is hard to see in sunlight. Also set the ranger finder to minimum mode and take lots of measurements moving it slightly each time, that will help reduce the errors.
Not that I’ve done this sort of thing a few times…
The simple RTK solution would be 2x C099-F9P-1 (or -0,-2 depending on where you are in the world for different frequency radio links between them). Most electronic component suppliers will have it, of my local gotos digikey and mouser both stock it, farnell doesn’t. the ublox site
It’s gone up a bit since I last looked, currently they are ~£250 each. So depending on budget that may not be an option.
If you happen to be somewhere with free RTK corrections available (some places the state/local government operates a free network) or RTK2GO is listing a base station near you (although the reliability of them is questionable) then you could possibly get away with only one receiver.
Hi leapslabs,
Today I did the outdoor test on the 47m x 27m field (6 anchors)
The accuracy of the tags was great, less than 10cm.
The reading speed of the stopped tags was optimal (less than 100ms).
But I had two issues:
1- Compared to the indoor test, in a quarter of smaller dimensions, the speed of reading the positions of the tags dropped a lot when the tags move (3-5 seconds to get the positions), However when the tags are stopped the speed of reading back to being very fast (less than 100ms).
I configured the tags with 100ms for “Normal update rate” and "Stationary update rate).
I’m using a tag as a listener, connected to a pc to read the tag positions.
Initially, I am using batteries in the anchors and tags.
After a while, it was necessary to bring the tags closer to the listener to get the readings, I don’t know why…
Is it because of the level of the batteries that were falling?
2- As I’m using the equipment outdoors, I initially did the test with plastic protection boxes on the anchors and tags (because I have to protect it from the rain), but I couldn’t read the positions of the tags…
Did the plastic enclosures block the signal?
I need a quick reading of tag positions (at least 100ms).
What could I be doing wrong?
Thanks a lot for the help.
Hi AndyA,
Today I did the outdoor test on the 47m x 27m field (6 anchors)
The accuracy of the tags was great, less than 10cm.
The reading speed of the stopped tags was optimal (less than 100ms).
But I had two issues:
1- Compared to the indoor test, in a quarter of smaller dimensions, the speed of reading the positions of the tags dropped a lot when the tags move (3-5 seconds to get the positions), However when the tags are stopped the speed of reading back to being very fast (less than 100ms).
I configured the tags with 100ms for “Normal update rate” and "Stationary update rate).
I’m using a tag as a listener, connected to a pc to read the tag positions.
Initially, I am using batteries in the anchors and tags.
After a while, it was necessary to bring the tags closer to the listener to get the readings, I don’t know why…
Is it because of the level of the batteries that were falling?
2- As I’m using the equipment outdoors, I initially did the test with plastic protection boxes on the anchors and tags (because I have to protect it from the rain), but I couldn’t read the positions of the tags…
Did the plastic enclosures block the signal?
I need a quick reading of tag positions (at least 100ms).
What could I be doing wrong?
Thanks a lot for the help.
You’re getting into the specifics of the PANS system and the hardware you are using. I’ve not used either, they didn’t do what I needed.
I believe that PANS does some averaging so it may be that if you are moving above a certain speed it decides the values are changing too much and so untrustworthy. Or it may be when moving the ranging success rate drops due to obstructions (it’s very easy to accidentally stand in the way while moving things) which causes the less reliable position calculation. Or I could be completely wrong. @leapslabs is the one to ask about this.
Plastic boxes will have a slight impact on the range but it shouldn’t be significant. I’d expect things like antenna orientation to have a far bigger effect on the results.
ad1) Could you explain a bit more? There is position averaging in the Node (average from last 3 position - this cannot be turned off) . And there might be additional averaging enabled in web interface/ drtls app - this can be turned on.
Regarding the listener range - Im not sure what do you mean with closer - but it should have 20m range - depends on obstacles and etc.
re 2) yes some plastic enclosures can negatively affect the radio signals. Especially the water is a very good RF signal blocker.
Cheers
JK
@AndyA
FYI I received nice black 3D enclosure - they look pretty much normal - black. However they are made from some thermoplastic material with antistatic coating 
, you never know …
Cheers
JK
Hi JK,
I initially used plastic protective cases. however with them, I believe that the signal dropped so much that I couldn’t even receive the information through the listener (connected to a pc) that is about 10m from the first anchor (which surprised me, I didn’t expect to block the signal that way).
When I removed the anchors from the plastic boxes I was able to receive the tag position readings.
However, these tags had to stay about 2 meters from the listener to work, further away from that, it stopped receiving the information.
These readings that I am referring to were captured via a listener connected to the PC, when the tags are stopped, I got very fast readings (about 3 every 100/ms), but when the tags move, the readings drop to 1 every 3 seconds. (I set it to 100ms for “Normal update rate” and "Stationary update rate)
I wrote a code in Python that connects to the tag listener via USB and executes the “lec” command, and that way I receive information about the positions of the tags).
When I installed it in a room (5m x 4m) using 4 anchors, the readings both with the tags stopped and in motion were very fast (about 3 readings every 100ms)
The area I’m using is 47m by 27m, with no obstacles, and I’ve installed 6 anchors, 3 on each side, over 47m.
I was not able to view the tags in the android app via cell phone, perhaps because of the bluetooth range in this large area.
I don’t know if I’m providing you with all the information you need to understand and help me, but I really need to quickly access (100/ms) the positions of the tags via PC in this area.
Thank you very much for your help JK