LEDzep – Distance measurement model based on RSSI


We did our first team presentation on monday showing our PSSC. We spent our entire sunday preparing it and we devided then our tasks. I’m in charge of positioning system. I presented to you a solution with IR technology. It seems to be now a little bit to difficult and unreliable (video processing especialy).

It seems to be better to use the received ble signal to deduce distances. In fact I’ve read at least four articles showing how to use Received Signal Strength Indication (RSSI) of BLE in order to deduce distances. I’ve found also a system that seems to work (but not very precise). It’s made by Apple but it can be use on Android devices. It’s called Ibeacon and Apple said that they are a real good solution for indoor localisation. But many users on youtube shows that the system is not so many precise if the user keeps its phone on his pocket. But could it be a solution for our Ballon?

We can imagine to use something like Ibeacon (Drops could be helpfull dear Drops&Roses 😉 ) in our test rooms. We will then analyse RSSI signals and find our relative position. The formula that we should use here is: “RSSI[dbm] = −(10.n log10(dist) − A)”.  Where A is a particular constant calculated when we receiver is 1 meter away. If we choose this solution, we could also use smartphones as transmitters. And this seems to be very interesting. For example, we would be able to ask ballons to follow the App user…

LEDzep – Team meeting and preparation for monday presentation


We’ve been working the entire afternoon on our project. We first worked on the localisation problem. Then we agreed on the different characteristics of our project in order to prepare the monday presentation. We have almost finished the PSSC.

How can we localise our balloons? They are several ways to do that but all include a landmark on the ground. Can we do without it? Or how can we minimize it number and it size? We thought to work with infrared technology. Can we use the balloon to diffuse an infrared light that a camera on the ground will track? It would be then possible to recover  φ and Θ angles as you can on this diagram. And if we link this solution to an altimeter, then we can reconstruct the relative position to the camera in the spherical coordinate system.

IR positioning system for LEDzep


We would use a prism in order to have a 360° vision and the camera system could also be embeded in a “master” zepelin in order to have a complete embeded system. This solution means that we can measur the altitude -> is there reliable altimeters?
As a solution for the camera module, we thought to use the wiimote one. This small and lightweight module returns directly the cartesian coordinates of the 4 lightest IR points with a good frequency (200Hz). But maybe it Would be better to make our own module.