WDMAM World Digital Magnetic Anomaly Map
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 2 arc-minutes, the latest WDMAM version 2 [Dyment et al., 2021] grid is now available for remote use in GMT.
Usage - World Digital Magnetic Anomaly Map
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):
Code |
Dimensions |
Reg |
Size |
Description |
|---|---|---|---|---|
01d |
360 x 180 |
g,p |
94 KB |
1 arc degree global WDMAM (2 min @ 111 km) |
30m |
720 x 360 |
g,p |
329 KB |
30 arc minute global WDMAM (2 min @ 55 km) |
20m |
1080 x 540 |
g,p |
695 KB |
20 arc minute global WDMAM (2 min @ 37 km) |
15m |
1440 x 720 |
g,p |
1.2 MB |
15 arc minute global WDMAM (2 min @ 28 km) |
10m |
2160 x 1080 |
g,p |
2.5 MB |
10 arc minute global WDMAM (2 min @ 18 km) |
06m |
3600 x 1800 |
g,p |
5.7 MB |
6 arc minute global WDMAM (2 min @ 10 km) |
05m |
4320 x 2160 |
g,p |
9.3 MB |
5 arc minute global WDMAM (2 min @ 9 km) |
04m |
5400 x 2700 |
g,p |
14 MB |
4 arc minute global WDMAM (2 min @ 7.5 km) |
03m |
7200 x 3600 |
g,p |
24 MB |
3 arc minute global WDMAM (2 min @ 5.6 km) |
02m |
10800 x 5400 |
p |
52 MB |
2 arc minute global WDMAM (2 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 data set will be used (@earth_wdmam.cpt)
Technical Information - World Digital Magnetic Anomaly Map
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 - World Digital Magnetic Anomaly Map
Lesur, V., Hamoudi, M., Choi, Y., Dyment, J. and Thebault, E.,, 2016: [https://doi.org/10.1186/s40623-016-0404-6].