A lot of questions so here’s at least some answers I know.
You’re right, the user manual there doesn’t have a radiation plot at all, only an approximation based on tracking range. It doesn’t explain anything about up and down but data from other parts indicate the functional pitch angle to be +/- 35 degrees. The “Up” and “Down” labels on the left image are necessary to define the positive and negative azimuth values.
Yes, the concentric circles are tracking range in two-meter increments. Up and down (pitch) is not represented and would require figuring out the proximate blind spot. The offset of the range values doesn’t help with seeing dissymmetry, but there is a slightly better range at an azimuth of -30 and -45 degrees.
Visualize it as the sensor stuck to a flat wall crossing from side to side at 90 degrees, with the PCB antenna pads facing toward 0 degrees at the top and the ‘down’ as shown in the left image toeward the ground. It can do its tracking out to 8m for anthing directly in front of it, a bit over 7m for things 15 degrees to either side, just over 6m for things 30 degrees to either side, and about 5m for things 45 degrees to either side. Then only about a meter for things 60 degrees to either side. So while it has a maximum range of 8m, the ‘true tracking area’ is only about 5m out in a 90 degree cone.
The whole ceiling mount thing is honestly a tricky thing. The LD2450 is made to map position, speed, and vector in a 2D plane across the azimuth of the sensor. Think of it as a flat fan of sensing down from the ceiling that reports where up to three distinct objects are located and how fast they are moving in which direction on the plane of that fan. But most humans will walk through that plane, not move up and down and left and right inside it. ‘Shining’ down from above means it can only see what is directly below it in a narrow zone.
So the final two questions… They sell them because fall detection and narrow zoning requirements can make use of the ceiling mounts. For example, hospitals, nursing homes, and retirement homes. Places where knowing the information about something moving up and down is important.
As for tweaks to make the ceiling position slightly better? It’s good for a specific purpose that is probably not the purpose you want it for. To have view of the whole room, you need numerous ceiling units with slightly overlapping views - think of spotlights in recessed ceiling fixtures and you want even coverage of light around shoulder level. It requires a lot of light fixtures.
Long story short(ish):
Ceiling mounting is meant to monitor a small region and focus on how high the moving object is. 45 degrees means that at the ground, the furthest to the sides it can see further than a meter is the same distance as the height of the ceiling. Useful for fall detection and tracking a small area but ignoring things at specific heights, like a pet near the ground.
Scanning an entire room requires wall mounting.
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