I am currently working on a project which seeks to utilize a tri-axial IMU to measure gravity anomalies caused by density variations in planetary crusts.

The instrument will be attached to a Helikite balloon at a maximum altitude of approximately 30 meters and towed by a rover. I understand the errors associated with IMU data, however, I am having some difficulty understanding how to implement the different corrections to the data.

Is a rotation matrix/quaternions required in order to shift the gravity vectors into the earth/navigational frame?

Also, any advice on filter techniques to help account for drift (e.g. Kalman filter) would be immensely helpful. My field of knowledge is earth/planetary science so I'm not too familiar with these kinds of techniques.

  • $\begingroup$ I'm really no planetary scientist, but, hm, since an IMU detects gravity as downward acceleration, and since "balloon" implies "atmosphere": how would your system detect small gravity variations while suspended in the atmosphere, which on all planets I'm aware of is by far not a constant-pressure static gas volume, but subject to pertubations? Wouldn't the acceleration by these be many, many orders of magnitude larger than any gravity pertubations on a planet with a solid crust? To help you answer your question, we'd need a mathematical model that describes how you model these anomalities. $\endgroup$ – Marcus Müller Nov 12 '19 at 22:55
  • $\begingroup$ And: "towed by a rover" sounds like you have very random and very strong accelerations that will, unless you have an extremely specific way in which you can tell gravity anomalities from being accelerated by mechanical pull, totally make your measurement impossible? $\endgroup$ – Marcus Müller Nov 12 '19 at 22:58
  • $\begingroup$ While you're worrying about Great Big Error Sources -- how do you intend to figure out the orientation of the IMU? If you're looking for the direction of the gravity vector with respect to the geodetic, you're going to need to know which way your IMU package is pointing. $\endgroup$ – TimWescott Nov 13 '19 at 0:50
  • $\begingroup$ Provided that there are two IMUs (one for reference on a stabilised platform and one for measurement),you would be able to obtain a differential measurement which could provide SOME approximation to the gravitational field AFTER you have cross referenced it with known models (taking TIDE into account too). Depending on your accuracy, the biggest challenge would be the actual measurement.How are you going to carry that out? Atomic clock? Laser accelerometer?Satelites are free of these problems, their orbit is relatively stable and therefore can measure the grav.field more accurately and easily. $\endgroup$ – A_A Nov 14 '19 at 13:42

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