WDMAM World Digital Magnetic Anomaly Map

_images/GMT_wdmam.jpg

The WDMAM (World Digital Magnetic Anomaly Map) is an international scientific project under the auspices of IAGA (International Association of Geomagnetism and Aeronomy) and CGMW (Commission for the Geological Map of the World), aiming to compile and make available magnetic anomalies caused by the Earth lithosphere, on continental and oceanic areas, in a comprehensive way, all over the World. At 3 arc-minutes, the latest WDMAM version 2 [Dyment et al., 2021] grid is now available for remote use in GMT.

Usage

You access a global WDMAM grid by specifying the special name

@earth_wdmam[_rru[_reg]]

The following codes for rru and the optional reg are supported (dimensions are listed for pixel-registered grids; gridline-registered grids increment dimensions by one):

WDMAM World Digital Magnetic Anomaly Map. An asterisk denotes tiled datasets.

Code

Dimensions

Reg

Size

Description

01d

360 x 180

g,p

94 KB

1 arc degree global WDMAM (3 min @ 111 km)

30m

720 x 360

g,p

329 KB

30 arc minute global WDMAM (3 min @ 55 km)

20m

1080 x 540

g,p

695 KB

20 arc minute global WDMAM (3 min @ 37 km)

15m

1440 x 720

g,p

1.2 MB

15 arc minute global WDMAM (3 min @ 28 km)

10m

2160 x 1080

g,p

2.5 MB

10 arc minute global WDMAM (3 min @ 18 km)

06m

3600 x 1800

g,p

5.7 MB

6 arc minute global WDMAM (3 min @ 10 km)

05m*

4320 x 2160

g,p

9.3 MB

5 arc minute global WDMAM (3 min @ 9 km)

04m*

5400 x 2700

g,p

14 MB

4 arc minute global WDMAM (3 min @ 7.5 km)

03m*

7200 x 3600

g

24 MB

3 arc minute global WDMAM (3 min original)

See GMT remote dataset usage for when resolution codes are optional or required. All of these data will, when downloaded, be placed in your ~/.gmt/server directory, with the earth_mag files being placed in an earth/earth_wdmam sub-directory. If you do not specify a CPT, the default CPT for this dataset (@earth_wdmam.cpt) will be used.

Technical Information

We scale and reformat the original data to take up very little space so that downloads from the servers are as fast as possible. For the WDMAM grid this means we chose 0.3 nTesla as the smallest data unit, which is well below the uncertainties in the model. Data are scaled and shifted to fit in a short integer grid that is highly compressed by netCDF lossless compression and chunking. The data are reported in nT.

Data References

  1. Lesur, V., Hamoudi, M., Choi, Y., Dyment, J. and Thebault, E., 2016: [https://doi.org/10.1186/s40623-016-0404-6].