<P> A third model, produced by the Goddard Space Flight Center (NASA and GSFC) and the Danish Space Research Institute, uses a "comprehensive modeling" approach that attempts to reconcile data with greatly varying temporal and spatial resolution from ground and satellite sources . </P> <P> For users with higher accuracy needs, the United States National Centers for Environmental Information developed the Enhanced Magnetic Model (EMM), which extends to degree and order 720 and resolves magnetic anomalies down to a wavelength of 56 kilometers . It was compiled from satellite, marine, aeromagnetic and ground magnetic surveys . The latest version, EMM2015, includes data from The European Space Agency's Swarm satellite mission . </P> <P> Animals including birds and turtles can detect the Earth's magnetic field, and use the field to navigate during migration . Some researchers have found that cows and wild deer tend to align their bodies north - south while relaxing, but not when the animals are under high - voltage power lines, suggesting that magnetism is responsible . Other researchers reported in 2011 that they could not replicate those findings using different Google Earth images . </P> <P> Researchers found out that very weak electromagnetic fields disrupt the magnetic compass used by European robins and other songbirds to navigate using the Earth's magnetic field . Neither power lines nor cellphone signals are to blame for the electromagnetic field effect on the birds, according to the new study published in the 8 May 2014 edition of the journal Nature . Instead, the culprits consist of frequencies between 2 kHz and 5 MHz, such as AM radio signals and ordinary electronic equipment that might be found in businesses or private homes . </P>

What do you understand by the axis of the earth