I had a look at your DWM1001 Modules and was wondering about the position of the tag relative to the anchor(s).
From the documentation I can only determine, that the tags position refers to the anchors positions.
See “DWM1001 System Overview (OP-DWM1001-System-Overview-2.0)”
The DRTLS uses a single-sided TWR scheme, in which tag ranges with up to four anchors, and then calculates its own location with respect to the anchors’positions, which it has learnt from the
Beaconmessages. It needs a minimum of three anchors to calculate a location.
Unfortunately I cpouldn’t find a reference to what this position actually refers to.
Simply, if the position of the tag is represented as a vector (X,Y,Z)
where would be the position X=0; Y=0; Z=0 or in other words, the root of the coordinate system?
Is it the center of the anchors participating in the RTLS or is it a predefined location?
The position is relative to the the anchors coordinate system.
Usually, one anchor is used as the point of origin (so for example 0.0m 0.0m 1.8m). In that situation, the tag will basically return 0 0 0 if it is at the same position of this anchor.
If you decide not to set an anchor to 0 0 0, then you still need to set this 0 0 0 arbitrary in your environment and all anchors coordinates must be relative to this origin point.
It does not have to be, in my network it is not the case. Having the initiator in a central position is good to ensure multiple anchors will receive signal from it. It makes the network more reliable.
The origin position is usually on the extremity of the network. For example, you set it on the angle of a building and calculate position of anchors from there.
It is really up to the user to decide what works the best for him.
There is another question I’d like to ask if possible.
I’m thinking about a scenario where multiple anchors are supposed to be deployed around a building. On a vehicle which might / or might not be in range of the anchors I’d like to place one or more tags.
The vehicle is supposed to support it’s navigation with additional RTLS data if in range of the anchors.
Would it be possible to receive RTLS data from the tag directly or is this only possible vi an achor?
In the later case would it suffice to place a single anchor on the vehicle, that would attach to the PANS when in range?
I am not completely sure what you mean by RTLS data.
Note that in PANS, the tag is performing the calculation of its position when it can range to 3 or 4 anchors.
So as long as your vehicle is in range with 3-4 anchors, you will have position directly from the tag (which will be in the vehicle). If the tag range to 0-2 anchors, it will provide only range to those anchors and no position.
another question regarding information from tags in PANS, if I may.
Let’s assume I got an anchor network setup and a single tag enters this network.
Additionally a Gateway (Raspberry Pi + DWM1001) is permanently in the range of this single tag, but not necessarilly also in the range an anchor.
Would the gateway receive information from the tag, if the tag has access to 1-2 anchors, therefore distance data to achors in range? If not would it be right to assume the tags inform the gateway only about their position data?
I have total 4 DWM1001-Dev. Having 3 as anchors and 1 as tag.
Among anchors, one being set as initiator and the other two as active anchors.
I connected my tag to my computer via USB and use tera term. I only get the output for the distance between tag and individual anchors. The output of my position remains as (0.00, 0.00, 0.00) for all 3 anchors. I did not pre-set any coordinates for my individual anchors.
Is it possible to auto calibrate it’s own location (coordinates) by itself?