The Geomagnetic Module (gdt.core.geomagnetic)

Introduction

The Geomagnetic module primarily provides a base class for defining a South Atlantic Anomaly (SAA) polygon. The SAA is a region of high radiation as it is caused by the closest approach of the Van Allen belt to the Earth’s surface. Most gamma-ray detectors need to be deactivated whenever they pass through the SAA, and the SAA boundary may be different depending on altitude and observing energy range. The SouthAtlanticAnomaly class is a container with some convenience functions for an instrument’s SAA boundary definition, although, in general, it can be used to define any other exclusionary region.

For Developers:

To use the SouthAtlanticAnomaly class, we need to subclass it and define the latitude and longitude vertices of the boundary within the class.

>>> from gdt.core.geomagnetic import SouthAtlanticAnomaly
>>>
>>> class MySaaRegion(SouthAtlanticAnomaly):
>>>     _latitude = [-30.000, -19.867, -9.733, 0.400, 2.000, 2.000, -1.000,
>>>                  -6.155, -8.880, -14.220, -18.404, -30.000, -30.000]
>>>     _longitude = [33.900, 12.398, -9.103, -30.605, -38.400, -45.000, -65.000,
>>>                   -84.000, -89.200, -94.300, -94.300, -86.100, 33.900]

Here we set two mandatory class variables, _latitude and _longitude, which represent the vertices of the polygon. Then we can create an instance:

>>> saa = MySaaRegion()
>>> saa.latitude
array([-30.   , -19.867,  -9.733,   0.4  ,   2.   ,   2.   ,  -1.   ,
        -6.155,  -8.88 , -14.22 , -18.404, -30.   , -30.   ])
>>> saa.longitude
array([ 33.9  ,  12.398,  -9.103, -30.605, -38.4  , -45.   , -65.   ,
       -84.   , -89.2  , -94.3  , -94.3  , -86.1  ,  33.9  ])

There are some convenience functions provided, such as determining if the region is a closed polygon:

>>> saa.is_closed()
True

and if the polygon is convex:

>>> saa.is_convex()
True

Reference/API

gdt.core.geomagnetic Module

Classes

SouthAtlanticAnomaly()

A base class for a South Atlantic Anomaly (SAA) boundary in Earth latitude and longitude.

Class Inheritance Diagram