Its main use is to give the current magnetic declination to correct a magnetic compass.
This application is most useful for those hiking and traveling without topographic maps in unfamiliar territory. A magnetic compass can be off by many 10's of degrees in parts of the world.
This application is also useful for correcting the magnetic declination of old topographic maps and navigation charts. The change in declination per year is surprisingly high.
To use this version of GeomagInfo you must install a Ewe¹ VM (Virtual Machine) on
your computer. Ewe is a version of Java which runs on a variety of desktop and handheld
computers. It is very compact and efficient. It uses only about 2 Mbytes of memory.
To learn more about Ewe please read the introduction on the Bray Mobile Applications page.
The first thing to do is to install the Ewe VM on your computer(s), if not already installed.
Follow the instruction found on the Ewe
Download and Installation Page for your computer. The Ewe installer will create directories
on your computer and put the Ewe VM files in them.
After Ewe is installed find the Ewe directory. For example, in a Windows Desktop it will be where you told the installer to install it, and in the Pocket PC it will (probably) be in /Windows/StartMenu/Programs/Ewe.
There is no installer for GeomagInfo.ewe. The files in the geomag10Install.zip archive can be
put in any directory of your choice. However it is recommended that you put them in the directory
with the Ewe VM. Specifically the directory in which you find 'ewe.ewe'. This will make it easier
to find them if you want to change them, and when you add additional applications from
Bray Mobile Applications common files can be shared.
In particular the Location Data CSV Files are common to most of the applications at: Bray Mobile Applications. GeomagInfo can be a companion application with Riseset.ewe. If you intend to use it with Riseset.ewe you must put both of these applications in the same directory.
Once you find the proper directory, copy (or synchronize to your PDA), in whatever manner you do that on your computer, only the files in geomag10Install.zip you want into that directory. You may not need (or want) the .csv files or all of the Geomagnetic Models in your computer. You need GeomagInfo.ewe and one Geomagnetic Model file, and some Location Data CSV files. See About Geomagnetic Models to decide which ones you would like to install. Also, it is likely that you already have Location Data CSV files that you are using, so you may not want to copy the ones supplied.
Note: No matter what Regional settings are used on your computer(s), GeomagInfo always uses the '.' (period) as the decimal point, the ':' (colon) as the hour/minute/second separator, and the ',' (comma) as the data separator.
GeomagInfo should be ready to run now. Find GeomagInfo.ewe with your File Explorer, click on
it to try it out!
Using the Program
To use GeomagInfo tap the Locations button. Since you have not previously used GeomagInfo you
will be asked to first activate the desired model file (.cof), then open desired location file (.csv).
The 'File Chooser' will pop up to do the selections. After the Location Data CSV file opens, tap the
desired location (it will become highlighted) and then tap Compute.
The date displayed is current date. To change it tap the date and then the desired at in the Date dialog box.
Hopefully the program output is self explanatory. The three terms used are:
Inclination is the angle a vertical reading compass will show at the location.
Intensity is the magnitude of the magnetic field at the location. The units are nanoTeslas (nT).
There are two drop down menus:
The Location Data CSV Editor Application (LocEdit) is available at the
Bray Mobile Applications page. LocEdit makes it easier to
edit Location Data CSV files and more data is available. If you are intending to create your own
personal Location Data CSV files it is recommended that you get LocEdit.
About Geomagnetic Models
GeomagInfo computes data about the Earth's magnetic field using models created by the U.S. Geological
Survey, and the International Association of Geomagnetism and Aeronomy (IAGA).
These models have a life of 5 years, and are updated every 5 years.
Supplied with this release are 4 geomagnetic models.
Models WMM-2005.cof, IGRF-2005.cof, WMM-2000.cof and IGRF-2000.cof are World Magnetic Models -- i.e. have reasonable accuracy world wide. The 2005 models are current. The 2000 models are supplied for historical reasons.
Getting Updated Geomagnetic Models
The Geomagnetic Models are updated every 5 years, as explained in the next section. All available
models at the date of this release are included.
The next major release will be in 2010. (Probably late in 2009.) The URL to look for new or updated models is: http://geomag.usgs.gov. Also you can contact John M. Quinn, as discussed next.
When they become available, they can also be found at: Bray Mobile Applications.
Note: If you cannot start GeomagInfo becuase of an invalid
Geomagnetic Model (or any other reason), delete the file GeomagInfo.ini. It is located in the
same directory as GeomagInfo.ewe.
About the Geomagnetic Field and Geomagnetic Models
That portion of the geomagnetic field generated in the Earth's core is referred to as the Main magnetic field simply because it is the largest contributor to the total geomagnetic field. It ranges in magnitude between 20,000 nanoTeslas (nT) at the geomagnetic equator to about 65,000 nT at the magnetic poles.
Magnetic models, charts and maps which are used in a wide range of commercial and military navigation and attitude/heading reference systems must be periodically updated.
Typically, the Geological Survey predicts the magnetic field strength and direction, and the rates of change of these quantities, both on a regional basis and on a global basis, 5 years in advance, in accordance with international scientific recommendations set in the 1950's by the International Association of Geomagnetism and Aeronomy (IAGA). A continuous flow of new data involving millions of measurements, which must be reduced, extensively analyzed, corrected, culled, edited and prepared for modeling, is essential in order to make these predictions. The Geological Survey produces Regional Magnetic Models (RMM's) of the Main magnetic field and its corresponding Secular Variation for the 48 conterminous states, Hawaii, and Alaska, known collectively as the U. S. National models. The Geological Survey also generates World Magnetic Models (WMM's). These models in turn are used to generate regional, national, and global charts and maps for several Main and Secular Variation vector-magnetic-field components of the Earth.
Digital information generated from the U. S. National Models, and the USGS
and IGRF World Magnetic Models are available through the USGS/NGIC on-line and
off-line information services.
Send e-mail inquiries to John M. Quinn; or you may write, FAX, or phone him at:
National Geomagnetic Information Center
U.S. Geological Survey Box 25046 MS 968
Denver Federal Center Denver, Colorado 80225-0046 USA
TEL: +1 303 273-8475
FAX: +1 303-273-8450
The 2000 geomagnetic models supplied with GeomagInfo have been obtained from John M. Quinn.
About the GeomagInfo Algorithm
The algorithm used by the GeoMagenticInfo computation is derived from a public domain FORTRAN
program by John M. Quinn and associates. The entire package of PC geomagnetic programs and models
is available for download at:
As in the public domain FORTRAN, the computation uses up to a 12 degree polynomial. It is possible
that the underlying data supplied by the USGS and IGRF have coefficients which support higher degree
polynomials. The supplied *.cof data for GeoMagenticInfo is limited to 12 degrees.
GeomagInfo was created by
David W. Bray, Potsdam, NY.
Copyright © David W. Bray 2005, All Rights Reserved.
This archive may be freely redistributed, provided it is made available only in its complete, unmodified form with no additional files and for noncommercial purposes only. Any other use must have prior written authorization from: David W. Bray .
Unauthorized commercial use includes, but is not limited to:
¹ Ewe is developed by Michael L Brereton. We are indebted to him for his outstanding software product and making it freely available. Thank you Michael!
*Changes in Version 1.0
GeomagInfo Version 1.0 Bld:452 differs from original Version 1.0 Bld:418 in:
To be sure that your version is up-to-date check the Bld: number in the current description of GeomagInfo at: Bray Mobile Applications
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