Jules Verne Voyager: Tutorial


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For more information about our Voyager map tool, contact:   Lou Estey   (louunavco.org)
Last modified: 16 Jul 2014

Basic navigation     For this exercise, please load (click on map image below):

    link to tutorial version of Voyager: Earth http://jules.unavco.org/Voyager/Earth?grd=0&w=360

which brings up Voyager with Earth showing the land in black, water in blue, and coarse outlines of the major tectonic plates in cyan. Specifying grd=0 shuts off any texture underlay grid on the initial map and w=360 limits the map width to 360 pixels, so that this exercise will proceed quickly. (grd is a mnemonic for GMT "grd" or "grid" files, which is how our texture underlays are stored and accessed on the jules server, and =0 means we don't want any right now.) However, what you will be learning here applies to all instances of Voyager, no matter how you start it or what world you are exploring.

After a few seconds, you should have global map like:

    global map of Earth

Wait until you see the entire map plus its border before going to the next step. Notice that this is a global map, and that the applet buttons [Index], [Up], and [Down] are in dark lettering. This means you cannot use them yet.

Rubberband box out an area, that is use your mouse to click down (don't release up yet) and drag a box, say, on the Caribbean area. When you release the mouse button, the box highlighted on the global map is the "zoomed" region you have just requested:

    doing a zoom on the global map of Earth

After a few seconds, a "zoomed-in" map like:

    result of the zoom on the Caribbean

should appear. (Important note: Don't click on anything else until the new map image finishes, or you may initiate one or more new map requests based on a image you can't see yet!) Now notice that the buttons [Index] and [Up] are now in light lettering, meaning that either one can now be clicked.

First, click [Up]. This returns you to the original global map. Notice that the [Index] and [Up] buttons are back to dark lettering (they can't be clicked) because there is no index map possible for a global map and you can't go 'up' anymore. But now notice that the [Down] button is in light lettering (it can be clicked). This indicates that you have at least one (and right now, only one) zoomed map already in a zoom stack. Click on [Down]. Now the [Index] and [Up] are back to being in light lettering (they can now be clicked), and [Down] is in dark lettering (can't be clicked since you are now at the bottom of the current zoom stack).

Now click [Index] to generate an index map of the current local zoom map, and your should get something like:

      index or 'view from space' map

This is a ' view from space' (orthographic projection), centered on the current local map, which is shown in magenta outline. Notice that the [Index] button now says [Local]. This means that you are displaying an index map of some zoomed region. Click on [Local] to return to the local zoom map (and notice that the [Local] button switchs back to [Index]). The label of this button indicates what you can switch to, not what you currently are on. If you have been following these directions without deviation, you should now be back to your original zoomed-in map of the Caribbean.

Now you are going to "pan" on your current local zoom map. Click on some point on the map, say, maybe some Caribbean island that you recognize. Make sure you don't draw a box! This sends a request to draw a new map recentered on the selected point with the same scale as the previous local zoom map. The "pan" below was directly on Dominica:

    result of a pan in the Caribbean area

Not only does this new local zoom map have the same scale as the previous one, but it also has the same aspect ratio (same width and height in great circle degrees). Click on [Index] again, and you generate a new index map for this new local map:

      index map of the 'panned' map

You might have noticed that on every index map that the [Up] button is in light lettering, indicating that it is active. While on the current index map, click [Up] and notice that this returns you to the global map, from which you can click on [Down] to return to the map centered on your current local zoom map.

Now you are familiar with the basic Voyager navigation of zooming, panning, getting an index map and returning to the local map, and moving around in a simple one-level zoom stack.

Return to a local map.


Keep on zooming...     On any local map, whether global (the [Index] button is in dark lettering) or a zoom map (the [Index] button is in light lettering), you can continue to zoom or pan. Starting where you left off above, on your current local map, rubberband box around a small group of islands in the Caribbean, for example:

    second-level zoom
and when that map is finished, then zoom on any one island:
    third-level zoom; e.g., Dominica

You should now have a zoom stack with four local maps (one global, three zoomed-in). Experiment with the [Index], [Local], [Up], and [Down] buttons until you understand their functionality with a zoom stack. The same general rules that you learned above apply.

Important tip!    One feature you should notice about Voyager zooming compared to other Web map interfaces is that you are in control of the aspect ratio of the map image. It doesn't matter whether you want an image that is long horizontally and short, or square-ish, or tall and narrow: you can usually obtain any of these quite easily. (However, it is sometimes harder to do this at the poles just by doing the rubberband box zooming; see Advanced Help zooming for how to do this more easily near the poles using a direct URL zoom.)

The Voyager zoom stack is limited to 31 local maps (one global, 30 levels zoomed-in). However, you rarely need so many. Usually, only 2 to 6 zooms are required to find your favorite island in the Caribbean, favorite fjord on the coast of Norway, or some other tiny hide-away. For example, only 2 quick zooms were required to obtain this map roughly centered on Annenkov Island, which is a tiny rock of an island just off the southwest coast of South Georgia Island in the south Atlantic:

    Annenkov Island using two zooms

and Annenkov is only 5 km across! (A distance scale was added to the above map for scale; more about this below.)

Important tip!    It is also possible to do a zoom on the global local map to get the initial zoomed-in map directly centered on either the north or south pole, or do zooms that puts the north pole at the top center or south pole at the bottom center of the map, or to do a zoom on the global local map which spans the east-west longitude break on the global map. These types of modified rubber-band zooms are easy to do, but somewhat difficult to explain, and so are covered in Advanced Help zooming.

One feature to be aware of is that zooming (or panning) on any local map wipes out any zoom stack that you might have built previously from zooms on the local map you are now zooming (or panning) on. For example, if you return to the Caribbean example above, and then zoom (or pan) on the zoomed-in map of several islands, notice that when the new map is completed that the [Down] button is now inactive, i.e. you cannot now go down to your single island map using [Down]. Instead you must re-zoom to get back to the single island map. (You can still retrieve images that might become lost by doing an accidental zoom or pan, or recreate them exactly if necessary. This is covered in Advanced Help: Retrieving "lost" image maps.) Neither zooming or panning affects the zoom stack above ([Up]) from where you currently are working.

Now you should be completely comfortable with zooming, getting a index map of any zoomed-in map, and moving around in a multi-level zoom stack.


Keep on panning...     Recall that you pan (re-center) by clicking on any point on any local map:

  • global map panning: re-centers on longitude only (to the nearest degree)
  • any local zoom map panning: re-centers on selected point in both longitude and latitude

Experiment with your current zoom stack.

Recall from above that panning on any local map also wipes out any zoom stack that you might have built previously from zooms on the local map you are now panning on.

Also recall from above that the zoom stack up from the level where you are working is not changed by panning. Thus, you could continue to pan several times on one zoom level (same map scale) — in fact, all the way to the other side of the world — and then the zoomed-in map still available by clicking [Up] is in the original part of the world where you were exploring. If you are doing a lot of panning, this situation can sometimes be confusing.

Now you should be completely comfortable with zooming and panning, getting a index map of any zoomed-in or panned map, and so on without the added complication of changing any features (yet). We'll try changing features next.


Changing displayed map features     Next, we are going to add some more "simple" features to the maps you currently have. Go to the [Features:] menu and move down to the [distance scale] option and click on it.

First, notice that selecting this does not in itself generate a new map. Voyager allows you to change as many features as you want before creating the next map. Second, under the [Features:] menu, the selection list should now say:

    selected: scale L:f/bl O:blue Pl:c

(If you don't see anything — and this problem is browser and version specific — just click on black space below the [Features:] menu button and above the current map border — you don't want to initiate a pan by clicking on the map!)

Until we figure out a better way, this "selected" list is your mnemonic for the set of options that is currently set to be displayed when you do your next map request. scale refers to the distance scale you just selected, L:f/bl means that land will be filled with black, O:blue means that the ocean will be colored blue, and Pl:c shows that tectonic plate outlines will be shown using a "coarse" plate boundary model.

Next, go back to the [Features:] menu and select [Earthquakes] which will add earthquake locations (color-coded by depth) to your map and add an EQ to your selected list.

For the moment, let's suppose this is what you wish to see on the current map being displayed. This can be any local map (global or zoomed-in) or any index map. Click on [Redraw] which initiates a redraw of the current map projection with the current set of selected options. If you were on a zoomed-in local map, you will get back the same scale local map now with a distance scale and the positions of earthquakes (color-coded by their depth). If you were on the global local map or an index map, then you will only see the earthquake positions added, but not the distance scale. For example, this is the global map with both earthquakes and distance scale selected:

    Earthquake positions added as a feature

The distance scale is left off because all the global maps and the index maps are so non-linear that it makes little sense to draw the scale for these types of map. (The same will occur for some other selected options. For example, most labels are not put on the global map or index maps because the information is so dense that you would not be able to read it anyway.)

Now click on any active (light lettering) of the [Index], [Local], [Up], or [Down] buttons. Or do a zoom. Or do a pan. Whatever you do will now return a newly generated map with earthquake positions added, and a distance scale when requesting a zoomed-in local map.

You ask how you know what the different options under the [Features:] menu will bring up. For each world, these are explained in the link at the top of the Voyager page to the right of Getting Started, which, if on Earth will be:

which has a brief description of each option. You can also go to the page on

for more detailed background about the different datasets.

Next, go back to the [Features:] menu and deselect [Earthquakes] by clicking on it again. Now EQ should be absent from the selected list. Again try clicking on [Redraw], or moving around in the zoom stack with the button, or zooming, or panning. Now the images produced will be lacking earthquake positions, but continuing to show the distance scale on all zoomed-in local maps.

Experiment with selecting and deselecting features (many or one at a time) and creating maps by any of the above methods. Notice that you can only select one texture underlay grid at a time (that is, any option in the [Features:] menu below [--texture underlays--] and above [--image overlays--].) To deselect a texture underlay, select any other texture underlay, or click on the same texture underlay to deactivate it. (Except for SeaStar's SeaWiFS images: many SeaWiFS images are accessed by the two SeaWiFS biodiversity menu options [SeaWiFS bio: old->new] and [SeaWiFS bio: new->old] and the land reflectance menu options [SeaWiFS lrf: old->new] and [SeaWiFS lrf: new->old] which get into a menu loop of their own. Cycle through to the end of the SeaWiFS texture underlays, or click on some other type of texture underlay and then click that again to deselect all texture underlays.)

Also experiment with selecting and deselecting items in any menus to the right of the [Features:] menu and to the left of [Index]/[Local] button. These items work the same way as image overlays in the [Features:] menu.

You should now be thoroughly familiar with using the Voyager applet except for the [pop-up:] menu which is covered next.


Saving an image     Obviously you cannot use the browser in the way you would be able to with HTML text to save an image, because clicking on the map image (using any mouse button) initiates a pan and then generates a new map. Instead, we provide a mechanism to save the current map image:

Go to the [pop-up:] menu and click on the [Save image] option. This brings up the Save Image page, and then just follow the directions. To save the GIF image which is currently being displayed on the Voyager applet, click on the GIF link, and then use your browser in the usual way, probably using the browser {File} menu to select {Save}, or {Save As ...}, or {Save Image As ...}, or something equivalent, depending on which browser you are using. You are also provided with a Voyager URL which can be used to directly recreate the image; it is your responsibility to save the URL if you think you might need to exactly recreate the image sometime in the future.

For most images, you can also save PostScript as generated by Generic Mapping Tools (GMT). The only current exception is any image using the regular ARC Science Simulations' Face of the Earth ™ texture underlay ([Face of the Earth] option under [Features:] menu on Earth).

Be sure to read the acknowledgements section on the Save Image page and give proper acknowledgements when you use an image for anything beyond personal use.


Other [pop-up:] menu items     Under the [pop-up:] menu are options which pop-up one or more browser pages — assuming that your browser to set to allow pop-ups from jules.unavco.org! [Save image] is discussed above.

Click the [ancillary] menu option to get to extra (ancillary) information concerning the items that you currently have selected on the map, which will include legend information depending on the current map selections.. Selecting this option may bring up more than one browser window! Additional links to investigate may occur on the ancillary pages. (Note: Some of these pages have links that may have broken with time, or the ancillary information page may not yet be created. Please inform us of any problems.)

The last buttons are short-cuts to some of the best Web sites for planetary information summary:

    Click the [Wikipedia] menu option to get directly to the Wikipedia (English) page for the world you are exploring.

    Click the [VSS] menu option to get directly to Calvin Hamilton's Views of the Solar System (English) page for the world you are exploring.

    Click the [9-P] menu option to get directly to Bill Arnett's The Nine Planets page for the world you are exploring.

    Click the [PDS] menu option to get directly to Caltech/JPL's Planetary Data System Welcome to the Planets page for the world you are exploring (except moons, which link to the home world page).


Comments, questions, problems about Jules Verne Voyager? Send mail to   Lou Estey   (louunavco.org)

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Jules Verne Voyager: Tutorial last modified on Wed, 16 Jul 2014 15:03 UTC
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