GOM - the Global Overlay Mapping System

How to use the Overlay Mapping System

This user-guide is designed to be read whilst looking at the Global Mapper Screen. Open both windows on your monitor, or print out this topic before opening the Global Mapper.

Start the Global Mapper by clicking on its icon. The screen that opens in front of you shows the Software and Overlay versions, and gives the current licensing information. (If the program has not been licensed, it will show my own postional information.) Above the main window is a standard Windows menu bar, that we are all familiar with. The first 7 of the labels: North America,South America, Europe, Africa, Asia, Oceania, and Polar, will take you straight to the maps. The other 2, Locate and Help, are used later on.

The first thing to do is to chose one of the 37 maps. These are of two types, the 8 continental maps, and the 29 sub-continental maps. To select & load any map, simply position your cursor and click on one of the first 7 buttons on the toolbar. A box will appear below showing you the available maps for that continent: first the continental map, and then the sub-continental maps. Click on one now to load a map of your choice.

When the map loads, you are initially presented with only the background layer. This contains the basic land and country outlines, plus the names of relevant water features, seas, and oceans. On top of that layer has been loaded the the first of the overlays: 'Country', which shows the filled country outlines, with region borders. The fact that it is turned on is indicated by the colored 'Country' button on the toolbar at the top of the map. Try turning the 'Country' overlay off and on again, by clicking on the colored button.

You can now add any of the other 11 layers, by clicking on the 11 other large buttons above the map. They are, left-right:

  • CQ Zones, defined by color or border.
  • ITU Zones, defined by color or border.
  • Time Zones, defined by color or border.
  • Colored relief or topographical map
  • Grid Locator mesh, with added grid locator information.
  • Lattitude and Longitude mesh, with regular number idents.
  • Country, regional, and island names.
  • Capital and other major cities.
  • Amateur Radio prefixes, and prefix borders.
  • IOTA code numbers, corresponding to the RSGB system.
  • Flags of the World, modified in aspect-ratio to give a constant size.

You can turn on one or more overlays simultaneously, to compare how the data relates. The layer that is currently on top is indicated by the horizontal colored line below the buttons. To bring a buried layer to the top, simply turn it off then on again. When a new map is selected, any existing layers will be turned off automatically.

Whilst a map is displayed, a variety of very accurate positional, distance, and bearing information is displayed on the status bar, at the bottom of your browser screen. For more information about this, visit the Status Bar help-page, by clicking HERE.

An extra feature with every map, is the dragable Scale-Bar, which can be turned on and off by clicking on the 'Scale' button, located to the right of the upper tool bar. For more information about this, visit the Scale-Bar help-page, by clicking HERE. Note that the Scale-Bar is only dragable when it is the current top layer. In other words, if you turn it on, then turn on another overlay, you will not be able to drag the Scale-Bar about, as the new overlay takes precendence in the stacking order. To regain control of the Scale-Bar, simply turn it off then on again.

Now lets investigate the other two buttons on the main toolbar. The first of these is 'Locate'. Click it, and you are presented with 2 choices: 'Find' and 'Overview'. Click the first one of these, and the 'Find a Map-Feature' page will open. This page is a new feature of the Global Overlay Mapper, and a very useful one. It lets you locate a feature and identify a feature who's location you might not know. Lets try it now. Click the 'Select Map by Name' dropdown-box, and choose the last entry, 'IOTA Groups - SA'. You will notice that the dropdown-box below it fills up, showing the first IOTA group for South America, 'SA-001 - Easter Island'. Choose any IOTA group from the list, then click the 'Go' button to the right of it. The correct map will be loaded, and a flashing box will show the centre-point of that IOTA group. Click on the flashing box to hide it, if you wish. Turn on the IOTA overlay by clicking on the IOTA button above the map, and you will see that the one you chose is identified. Note that the actual label might have been re-positioned slightly, for clarity, or to position it to one side of a map-name or other feature.

The other button below 'Locate' on the main toolbar is 'Overview'. Click on it to load the 'Overview' page. This shows the maps available in the Global Overlay Mapper, split into 2 types, Continental and Sub-Continental. As you pass your cursor over the upper or lower world map, the screen will light up to show an available map. Click on the map to load it.

To check the latest version of Software and Overlays that you have, click on Help > About, on the main tool bar. For more information about this, visit the About-Button help-page, by clicking HERE. The other options, 'User Details' and Register are explained HERE and HERE.