EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution) compressed for NumPy

A compressed NumPy version of the EMAG2 (v3) global Earth Magnetic anomaly grid compiled from satellite, ship, and airborne magnetic measurements. The original CSV data was imported, transformed, and saved to a compressed NumPy archive as follows:

import numpy as np

mag_data = np.loadtxt('EMAG2_V3_20170530.csv', delimiter=',', usecols=(2,3,4,5,7))
lon_mask = mag_data[:,0] > 180.0
mag_data[lon_mask,0] -= 360.0
np.savez_compressed('EMAG2_V3_20170530.npz', data=mag_data.astype(np.float32))

The NumPy archive (contained in this repository) can be efficiently loaded in Python workflows. It contains the following columns:

1. Longitude - geographic longitudinal coordinates in decimal degrees (WGS84)
2. Latitude - geographic latitudinal coordinates in decimal degrees (WGS84)
3. SeaLevel - magnetic anomaly value at sea level (nT)
4. UpCont - magnetic anomaly value at continuous 4km altitude (nT)
5. Error - Error estimate (nT)

Code 888 is assigned in certain cells on grid edges where the data source is ambiguous and assigned an error of -888 nT.
Code 999 is assigned in cells where no data is reported with the anomaly value assigned 99999 nT and an error of -999 nT.

Reference

Brian Meyer, Richard Saltus, Arnaud Chulliat (2017): EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution) Version 3. National Centers for Environmental Information, NOAA. Model. doi:10.7289/V5H70CVX