# minimum working area

hi

We are working with 4 anchor and 1 tag system as like in the picture.

How accurate is the system with 4 anchors close together?(50 cm)

Can we calculate direction of mouse and position of mause ?

What is minumum working range of dwm1000 ?

Hi Smeric,

Measuring short distance is possible, there is a risk of accumulator saturation for very short distance though.

I wouldn’t recommend to place you anchor as described as the location engine will not perform very well. The geometric dilutionn of precision is too low to calculate an accurate location. Maybe look at this thread for more explanation : https://www.decawave.com/decaforum/showthread.php?tid=1338&pid=3870#pid3870

The system would perform much better if you place the anchors at 2m*2m square and track the mouse within the square.

Thak you,
Regards
Yves

I have a tool for calculating position uncertainty for a given geometry of beacons, it uses fairly standard DoP calculations to predict errors based on geometry.

I made the assumptions that range measurements have a random error from truth with a standard deviation of 5 cm and that everything is at about the same height.

Feeding your setup into the tool I get errors of around 6 cm close to the tags increasing to around 30 cm at the edge of the 2 m circle.

Keeping everything else the same but moving the anchors to being equally spaced around the edge of a 2 m circle the errors remain around 5 cm in the middle but are now under 7 cm at any point in the circle.

As with any mathematical model these results are only a guideline but they make a reasonable starting point. Even if you assume that the system works just as well at very short ranges as it does at longer ones the maths indicates that you’re not going to get very good results with your planned configuration.