Using the Map and Map Inspector

The map shown in Rendezvous' main window can display different information in different forms.  The Map Inspector controls exactly what information is displayed and what form it takes.  You can display the Map Inspector by clicking on the Inspectors : Map... button in the main menu.  This panel will appear:

If the high resolution databases are missing, some of the selections will not be enabled.  Due to the size of the high-resolution databases, they are not included in the standard distribution.  If you would like them, they can be downloaded from this page.



Map Projection

You can change from the default Mercator map projection to an Orthographic (Globe) projection using the Map Projection area in the panel.  The selections marked "Rendered" produce topographic maps whose color represent elevation above sea level.



Map Boundary

The Map Boundary area shows the minimum and maximum values of the latitude and longitude of the Mercator Map.  You may change these values precisely by entering the desired value in the text field and pressing the carriage return button on the keyboard.  If however, the current map is an Orthographic projection, the Map Boundary options will look like this:

The View Latitude and View Longitude specify the location at the center of the view, in units of degrees.  The View Extent field specifies the magnification used in the display.  To zoom in on the earth, use a number smaller than 1.0.  To see more of the space around the earth (to display, for example, geo-synchronous satellites) use a number larger than 1.0.



Options

Solar Terminator

The Solar Terminator is the boundary between the area on the earth illuminated by the sun and the area that is not.  These areas may selectively be displayed by checking the Solar Terminator option.



Ground Trace

The Ground Trace is the path followed by a satellite.  The Ground Trace begins at the time value displayed in the Start text field of the Ground Trace Control area of the main window and ends at the time value displayed in the End text field of the Ground Trace Control area of the main window.  The increment of time used in the display is the value in the Delta T text field of the Ground Trace Control area.



Satellite Positions

The Satellite Position is the position currently occupied by the satellite.  The current time is measured as Mission Elapsed Time in seconds since the Epoch Date set in the Calendar.



Satellite Coverage

Satellite Coverage displays the area of the earth within which the satellite is above the horizon.  You may also think of this as the area of the earth which the satellite can see.



Satellite Illumination

Satellite Illumination displays the portion of the Ground Trace during which the satellite is not illuminated by the Sun as a white line.  Times during which the satellite is illuminated is colored blue or red depending on whether the satellite is a sensor or target.



Lunar Shadow

The Lunar Shadow option displays the shadow cast by the moon on the earth during a solar eclipse.



High Resolution

The High Resolution option causes the maps to use the high resolution boundary and topographical databases. This option is disabled if the high resolution databases are absent.



Political Boundaries

The Political Boundaries option toggles the display of countries and states.



Zooming the Map

In order to see the details of ground trace information, sometimes it is necessary to zoom-in on a specific area. In the Mercator Map, you can do this in two ways.  The easiest way is simply to click-drag a box around the area you would like to see.  The map will re-display using only the portion inside the box.  To un-zoom, shift-click anywhere inside the map.  You can also use the Map Boundary text fields in the Map Inspector to zoom into an area manually.  Set the minimum and maximum values for the latitude and longitude you desire, and press the carriage return.  The map will re-display using a box enclosed by the values you entered.

The Orthographic map can be rotated to a different orientation by click-dragging inside the map.  Dragging left or right will change the longitude of the viewpoint, dragging up or down changes the latitude.  The current longitude and latitude of the viewpoint is shown in the lower left corner of the map as you drag the mouse.

Here is a display of the main window for a ground trace of a complete orbit with all satellite display options selected. The map has been zoomed-in to show details more clearly. The portion of the ground trace which is colored white represents the time during which Mir is not illuminated by the sun.  The red trace is the Zarya Space Station module.





Other Interesting Odds and Ends - The Analemma

It was noticed many centuries ago that marking the sun's position at the same time each day traces out a figure that is shaped somewhat like an 8.  This figure is called the analemma.  In those days, they would place a stick in the ground and mark the tip of it's shadow every day.  Today we can use judicious values for Delta T and the End times and Rendezvous will trace this out for us.  We'll plot the sun once each week (instead of once a day) at 1:30pm GMT for a whole year:

If the Sun isn't loaded into the Target browser, load it like this:

o Click the Constellation : Open Targets button in the main menu
o Click the Platform pull-down menu button at the bottom of the Open panel, and select the PolynomialPlanets entry that appears near the bottom of the list
o Navigate to the Rendezvous.app/STATES/PolynomialPlanets.list file
o Click the OK button at the bottom of the Open panel

Select the Sun from the second column of the Targets browser:

o Click the PolynomialPlanets entry in the first column of the Targets browser
o Double-click the entry labeled Sun in the second column of the Targets browser

Now we'll set the date and the time increments:

o Set the Calendar to August 29, 1999 (this date is somewhat arbitrary)
o Set the Time to 13 : 30 : 00
o Enter the value 31449600 in the End text field (this is approximately the number of seconds in one year), and hit the tab key to move to the next field.
o Enter the value 604800 in the Delta T text field (this is the number of seconds in one week)
o Press the carriage return key on the keyboard

NOTE: If you press the carriage return with the value 31449600 in the End field while value 100 in the Delta T field, Rendezvous will have to calculate 314496 data points, and you'll be waiting a long, long time for it to finish.

After this procedure, zoom in on the figure 8 you'll see in the Atlantic Ocean.  It should look like this:

The red outline is the figure of the analemma.