Map Controls 
Map Controls menu can be accessed using the button available in the main menu shown in Figure 1. This button will start up a new sub menu which allows setting the desired map limits and map projection, adding a latitude and longitude grid, adding a legend, and zoom options Figure 2.

 
 


Set Map Limits
Set map limits button is used to set up a region of interest Figure 3. One can choose an already defined region, such as the Middle East and North Africa or North America, or type in the latitudes and longitudes of the area of interest.
 



Set Map Projection
Map projections in GEOID are done on the fly for all line, polygon, and point type data sets. The grids and images are kept in Equirectangular projection, as projecting any grid will take too long to accomplish on the fly. Using this menu users can set one of the available projections and define the projectionís parameters (Figure 4). After this point, until it is changed again, all mapping will use this specified projection. It is possible to change the projection at any time during a session. The default projection is Equirectangular. A warning message will be displayed if a user attempts to display an image file when a different projection is active. In this release there is no option of using other projections. This will be added to the system in future releases.
 



Lat/Long Grid
This button is used to add a latitude- longitude grid and grid labels to the map. A sub menu allowing a user to choose grid interval, label interval, and their locations appears on the screen  (Figure 5). After typing in the desired numbers and checking the "On" button, the grid is displayed once the "Done" button is pressed. It is also possible to set the label format with this menu. Grid label formats are DD, DDM, and DMS representing Decimal Degree, Decimal Degrees - Minutes, and Decimal Degrees - Minutes - Seconds, respectively. Both line and tic (cross) styles are supported in latitude and longitude grids. Labels can be placed on top, bottom, left, or right by highlighting the appropriate button.
 
 



Add legend
This button is used to add a legend for the map. GEOID automatically detects which data sets have been activated and generates a legend. The legendís scale (i.e., its size) can be changed by entering a scale factor (Figure 6). The majority of data sets will produce a legend if they are displayed. However, not all data sets can be seen in the legend. It is possible to have items like tectonic units, mine location, and crustal profile locations, but items like coast lines and country borders will not appear in the legend box. The default legend will appear at the lower right corner of the map. However, it can be moved anywhere in the page by clicking the Move legend button. Once this button is clicked, you need to define the new position and mark the lower left corner on the screen. By clicking the Cancel legend button the legend can be removed from the map.
 



Zoom in, Zoom out, Previous Zoom
These three buttons (See Figure 2) are used to set a zoom level. Instead of using the Set map limits option described above, one can use the zoom in button to zoom in on a region of interest directly from the screen. Once the Zoom in button is pressed, two corners of the area of interest must be marked on the screen. You can mark the corners in any order. The new map area will be redrawn when two points are marked in the screen. The Zoom out button zooms back to initial map limits. The Previous zoom option allows going back one step in zoom level.

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