Secondly, according to the needs of UAV location tracking, the paper analyzes the advantages and weakness of mechanical, magnetic sensing, GPS, ultrasonic, inertia and optics tracking technology.
We can describe quantities of electric magnetic field in different inertia system, and use Lorentz transformations to educe the transformations between them.
描述电磁现象的场量在不同的惯性系中有不同的量值，利用洛伦兹变换关系式导出它们之间的变换形式。
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The magnetic field of a low-inertia REPM DC servo motor with ferrite shielding case was calculated by the finite element method.