Trajectory Tool Tutorial


Step 1.  Load the trajectory tool.

After selecting the trajectory tool button, allow the trajectory tool to fully load in your browser.  If you are using a dial-up connection, it may take several seconds to see the loading bar.  The map will not be ready for use until the loading bar reaches 100%.

The trajectory tool has been designed for a 1024 X 768 screen resolution to provide sufficient map detail.  The image below displays how the entire trajectory tool should appear in your web browser.  If you load the tool and it does not fully fit into your browser window, we suggest that you temporarily increase your computer's video resolution.  For instructions on how to do this click here.

Step 2.  Select the start location.

If you know the latitude and longitude coordinates of your start location, you can simply enter those numbers into the labeled text boxes as displayed in the illustration to the right.

To select your start location by clicking on the map, begin by moving your cursor over the small map until the shaded area is over the geographic area of interest.  Click the shaded area and it will load into the large map.  You may then zoom a second time by clicking on a numbered quadrant (1-16) that appears in the thumbnail map.  The fully zoomed quadrant will then load into the large map.  In the example above, we first chose the middle shaded area, then quadrant number 11.  If you make a mistake and enter the wrong quadrant on either zoom level, simply click the text labeled "Zoom Out" (located directly above the thumbnail map) and try again. 

After successfully loading the zoomed street level map into the large map area, you are ready to choose your desired start location.  Notice that when you click a location on the map, it loads the latitude and longitude coordinates in the text boxes for you.  If you mistakenly clicked the wrong location, you can select another point on the map and the longitude and latitude coordinates will be updated automatically in the text boxes.

Step 3. Optional: View the monitoring site labels.

The red and yellow dots on the map indicate the locations of monitoring stations that collect wind data used to generate the trajectories.  To identify each monitoring station, hold the cursor over the station location for a few seconds and a label will pop-up with the name and CAMS number for that monitoring site.

Step 4.  Select the start date.

Click the box to the right of the date field to drop down the monthly calendar.  Use the arrows to scroll the months.  Click on the day from the appropriate month and year.  The pull down calendar will disappear and the selected date should now be displayed in the date test box.

Step 5.  Select the start time.

Use the arrow keys to choose the start time for the trajectory calculation.

Step 6.  Set the run time (in hours).

The run time is the length of time you want the trajectory to run. 

Example 1:
If you choose a "forward" trajectory and your start time is 5:00pm, the trajectory tool will calculate a trajectory that begins at 5:00pm and moves forward in time until 6:00pm.

Example 2:
If you choose a "backward" trajectory and your start time is 5:00pm, the trajectory tool will calculate a trajectory that begins at 5:00pm and moves backward in time until 4:00pm.

Step 7.  Select the trajectory type.

Next you need to determine if you want a "forward" or "backward" trajectory:

  • A forward trajectory provides an estimate of the path that air followed moving forward in time beginning at the start location.  Forward trajectories are often used to answer the question: “Where did the air go?”
  • A backward trajectory provides an estimate of the path that air followed prior to arriving at the start location.  Backward trajectories are often used to answer the question: “Where did the air come from?”

Step 8.  Create the trajectory.

Now that you have chosen your start location, start date, start time, and run time and selected either the forward or backward trajectory option, click the submit button to generate the trajectory.  After the trajectory is complete, you can zoom in by clicking on the quadrants, or zoom out by clicking on the “Zoom out” button located over the thumbnail map.  The trajectory you just created will remain on all maps until you either refresh the browser or resubmit a new trajectory.

The green dots along the trajectory path show the calculated locations at 5-minute intervals.  The trajectory locations are labeled at 15-minute intervals beginning at the start time.  The diameters of the trajectory position labels grow linearly at a rate of one mile per hour to provide a visual estimate of the uncertainty in the trajectory position as a function of time.

To print, select "file" then "print" in the browser menu and print page just as you would any web page.

For a full discussion of how the trajectory is calculated, click here.

Step 9.  Optional: Save/Bookmark location.

Save Location Feature:

  • To bookmark the start location for future use, click the "Save Location" link to save the latitude and longitude coordinates.

Step 10.  Optional: Favorites.

Favorites Feature:

  • When returning to the map click "Favorites" to recall previous start locations.

  • A window will open with the name, longitude and latitude of the saved locations.  Select the name of the location you want to pin point on the map and click "OK".  You will return to the map and the start point will now reflect your saved location.


Step 11.  Optional: Export trajectory coordinates.

Export Feature:

  • To export the longitude and latitude coordinates of the trajectory, click the "Export" button that appears after the trajectory is run.

Step 12.  Optional: Email trajectory.

Email Feature:

  • To email the trajectory to another person, click the "Email" button to create a link with all of the attributes to recreate the trajectory on another machine.  Both the "Email" and "Export" buttons appear only after the trajectory is run.

If you have any comments, questions, or problems with the web interface or the operation of the tool, please email Denzil Smith.  If you have technical questions about the data and calculation methodology used to generate the trajectory, email Gary McGaughey.  Click here to go to the trajectory tool.  Enjoy!