science

World Digital Magnetic Anomaly Map

World Digital Magnetic Anomaly Map is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand World Digital Magnetic Anomaly Map rather than just read about it. In short: The World Digital Magnetic Anomaly Map (WDMAM) was first made available by the Commission for the Geological Map of the World in 2007. Compiled with data from governments and institutes, the project was coordinated by the International Association of Geomagnetism and Aeronomy, and was presented by Mike Purucker of NASA and Colin Reeves of the Netherlands.

Key takeaways

World Digital Magnetic Anomaly Map belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect World Digital Magnetic Anomaly Map to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of World Digital Magnetic Anomaly Map from memory before moving on to harder problems.

Reference excerpt

The World Digital Magnetic Anomaly Map (WDMAM) was first made available by the Commission for the Geological Map of the World in 2007. Compiled with data from governments and institutes, the project was coordinated by the International Association of Geomagnetism and Aeronomy, and was presented by Mike Purucker of NASA and Colin Reeves of the Netherlands. As of 2007, it was considered to be "the first truly global compilation of lithospheric magnetic field observations." and further improvements dated to 2009 relate to the full spectrum magnetic anomaly grid of the United States and also data of global marine magnetic anomaly. Some of the magnetic anomalies shown in the WDMAM generally relates to the altitude level of 5 kilometres (3.1 mi). Some of the significant features represented are of the Bangui Anomaly in the Central African Republic, the Chicxulub crater, the Thromsberg anomaly, the Richat Structure, the Atlantic ridge, the Bay of Biscay, the Sunda Arc and the Paris Basin.

Background

WDMAM v1, 2007 In evolving the WDMAM the lithospheric data related to data acquired from satellites, data of aero-magnetic survey and marine survey, in-situ data gathered from field stations and observatories are to be collated analyzed together, and this would need an international joint effort. The map is the product of years of work, research and coordination by the International Association of Geomagnetism and Aeronomy (IAGA) and numerous small organizations around the world including GETECH, a project of Leeds University, and Juha Korhonen of the Geological Survey of Finland have also been involved. International collaboration has been the key to the project. Mike Purucker of NASA said of the collaboration: "There are literally hundreds, perhaps thousands, of organisations around the world which hold this kind of data. One should not underestimate the diplomatic efforts needed to secure support and data contributions from these organizations." Diplomacy was needed to acquire data from the Russians, Indians, and Argentinians and so on. It is available through the Commission for the Geological Map of the World. The map is compiled from a jigsaw of aeromagnetic surveys, incorporating both ground-based, airborne and marine magnetic data, but is incomplete. CHAMP, a German and Russian-built satellite which has been in orbit since 2001, has been of crucial importance to the map compilers. One of its principal achievements is that it has significantly improved the "pre-processing and the corrections applied to the CHAMP satellite measurements in order to obtain 'clean' satellite data compatible with ground data." However, it has some large gaps in data, which is a hindrance to studying trans-national tectonics, and could benefit from further satellite observational additions to improve its coverage. Several different models were put forward as candidates for WDMAM by groups from NASA, Leeds University, the Geological Survey of Finland, National Geophysical Data Center (NGDC) and GeoForschungszentrum Potsdam, all using the same base data. Following a review, the NGDC candidate was chosen to form the basemap. Specified to a grid of three arcminutes, the WDMAM v1 was based on the NGDC's EMAG3 (Earth Magnetic Anomaly Grid, 3 arcminute) dataset. The EMAG has since been improved into EMAG2 at a resolution of two arcminutes and fitted into the Enhanced Magnetic Model.

WDMAM v2, 2015

Composition According to the BBC, the "global map shows the variation in strength of the magnetic field after the Earth's dipole field has been removed (Earth's dipole field varies from 35,000 nano-Tesla (nT) at the Equator to 70,000 nT at the poles). After removal of the dipole field, the remaining variations in the field (few hundreds of nT) are due to changes in the magnetic properties of the crustal rocks." The map is graphically represented by illustrating those landmarks of high magnetism in red to yellow hues and those of lower or negative magnetism in blue hues. It can pick up numerous aspects of the earth composition, including the sea floor spreading under the oceans, and reserve deposits like iron ore at Kursk. It identifies some prominent magnetic anomalies on the African continent. The dominant factors for magnetic anomalies picked up on the map are "the thickness of the magnetised layer and the composition of the crust". Younger crust is typically thinner, and naturally has a lower number of magnetic materials.

References

Bibliography

External references Official website WDMAM download page

Worked examples

Example 1 — a first encounter with World Digital Magnetic Anomaly Map

Start with the simplest possible case. Write down what World Digital Magnetic Anomaly Map claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to World Digital Magnetic Anomaly Map before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about World Digital Magnetic Anomaly Map ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of World Digital Magnetic Anomaly Map

In research: World Digital Magnetic Anomaly Map appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses World Digital Magnetic Anomaly Map in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: World Digital Magnetic Anomaly Map is common in secondary-school and first-year university syllabi. It links to neighbouring topics 21st-century maps and globes, Magnetic anomalies, Projects established in 2007, so understanding it makes those chapters shorter.
In everyday life: Look for World Digital Magnetic Anomaly Map outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study World Digital Magnetic Anomaly Map in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what World Digital Magnetic Anomaly Map means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain World Digital Magnetic Anomaly Map out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is World Digital Magnetic Anomaly Map in simple terms?

Why does World Digital Magnetic Anomaly Map matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study World Digital Magnetic Anomaly Map?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on World Digital Magnetic Anomaly Map.