ultrazapp wrote: ↑
Fri Sep 01, 2017 5:38 pm
... I have just read the data sheet that Dave posted cover to cover and it tells me how it works, that it reads a magnetic field and the Gauss range that it measures but it does not tell me what area it is measuring. For example is it measuring the magnetic field on my desk, the room that I am in, my house or at an extreme my town?
I want to fly the Pi and the sense hat from a quadcopter and use the sense hats instruments to measure the environment at about 200 feet in altitude for a PhD project on honeybees, ultimately to produce a 3D graph/map of the area as we know that honeybees use the earths magnetic field to navigate. Guaranteed the first thing my supervisor at Uni is going to ask me is "What does it measure and over what physical area, and Er prove it son"
I have used the data produced from the sense hats magnetometer data to produce the attached 3D graph which as I thought shows magnetic peaks, troughs, valleys and mountain ranges that the bees are likely to use to navigate, but Im really struggling to put any meaning to the image as I have no idea of the physical area being measured as in Length x Height x Width?
It may be that you're misunderstanding what a magnetic field is.
The field strength only refers to one point in space. A mile away, a yard away, a nanometre away, it could be different.
The magnetometer has a physical size, and so averages the field strength over its volume, but the principle still applies - it's a measurement that refers to one point only
A honey bee has some mechanism for sensing magnetic fields (possibly lumps of ferrite - the mechanism isn't important) that averages forces over its volume.
If you were to look at a large-capacity disc drive, you'd find the data is written in the magnetic field structure on the surface, and the read head at any rate is smaller than a honey bee's sensing system, so it can sense smaller details of the field.
Go to a hi-tech physics lab and investigate the magnetic field of a hydrogen atom. You'll find that the field caused by the orbiting electron is ginormous, within the volume of the atom, but is cancelled out by other atoms close by (an angstrom or so) and by the proton rotating at the centre. The proton, in turn, is three "rotating" and "orbiting" quarks each with their own magnetic fields, though it becomes less meaningful to talk about their position or velocity at that scale, and the magnetic field strength becomes meaningless.