Magnetic airborne survey of Britain

This is a digitization of an airborne magnetic survey of Britain. Data are sampled where flight lines crossed contours on the archive maps. Contains only the total field magnetic anomaly, not the magnetic field intensity measurements or corrections.

Unfortunately, the exact date of measurements is not available (only the year).

Contains British Geological Survey materials © UKRI 2021.

Original source: British Geological Survey

Pre-processing: Source code for preparation of the original dataset for redistribution in Ensaio

import numpy as np
import pandas as pd
import pygmt

import ensaio

Download and cache the data and return the path to it on disk

fname = ensaio.fetch_britain_magnetic(version=1)
print(fname)

/home/runner/work/_temp/cache/ensaio/v1/britain-magnetic.csv.xz

Load the CSV formatted data with pandas

data = pd.read_csv(fname)
data

	line_and_segment	year	longitude	latitude	height_m	total_field_anomaly_nt
0	FL1-1	1955	-1.74162	53.48164	792	62
1	FL1-1	1955	-1.70122	53.48352	663	56
2	FL1-1	1955	-1.08051	53.47677	315	30
3	FL1-1	1955	-1.07471	53.47672	315	31
4	FL1-1	1955	-1.01763	53.47586	321	44
...	...	...	...	...	...	...
541503	FL-3(TL10-24)-1	1965	-4.68843	58.26786	1031	64
541504	FL-3(TL10-24)-1	1965	-4.68650	58.26786	1045	74
541505	FL-3(TL10-24)-1	1965	-4.68535	58.26790	1035	94
541506	FL-3(TL10-24)-1	1965	-4.68419	58.26787	1024	114
541507	FL-3(TL10-24)-1	1965	-4.68274	58.26790	1011	120

541508 rows × 6 columns

Make a PyGMT map with the data points colored by the total field magnetic anomaly.

fig = pygmt.Figure()
scale = np.percentile(data.total_field_anomaly_nt, 95)
pygmt.makecpt(cmap="polar", series=[-scale, scale])
fig.plot(
    x=data.longitude,
    y=data.latitude,
    style="c0.02c",
    fill=data.total_field_anomaly_nt,
    cmap=True,
    projection="M15c",
)
fig.colorbar(frame='af+l"nT"', position="jBL+h+w7c/0.2c+o1/2")
fig.coast(shorelines=True)
fig.basemap(frame="afg")
fig.show()