Urban Ocean Observatory at Davidson Laboratory

Overview & Control Panel Usage   (click here to close help

This page provides a real-time plot of the track of mobile stations, typically ships. You may view just the path of travel, or you may view various environmental sensor readings along the path. The plot is drawn using Google Maps, so that you may zoom in and out, drag the map to change location, and change the background.

The default plot for all vessels is the path of their travel. First select the vessel (if more than one is available) in which you are interested, and click Plot. The plot will default to the current day, and the date and time drop-downs may be used to change the date and time. If you change the Start Date, the End Date will automatically be set to the same date. The End Date may then be overridden. There is a 2-day limit for plots.

If you would like to view environmental sensor data along the path of travel, use the "Type of Data" drop-down to select the type of environmental data, and again click Plot. If you select anything other than Track the path shown becomes multi-colored; this is done to represent the values of the parameter and a color bar legend will appear.

Color bar legend value note: So that we may visually differentiate variations in environmental data as much as possible, the values associated with any color may change for each plot because of changes in range. For instance, if the salinity range for one plot is from 20 to 22 psu, then the middle of the colorbar will represent 21 psu. If on another plot the range is 24 to 32, then the middle of the colorbar will represent 28.

There are two markers that are used for plots: and The white tear with a sailboat overlayed with a red stop sign indicates the end of the plot and/or the most recent location of the vessel, if no plot has been drawn yet. The white tear with a sailboat is used for intermediate points along the track: While a plot is in progress, three red buttons, labeled "Pause", "Continue", and "Clear", will appear below the Plot button. Pressing Pause will stop the plot, and a red cone marker will appear at that point.

If you click on any of the markers, a Google Maps info window will appear, with the location, and date and time for that point. If you are tracking environmental data, such as salinity, the value at that point will also be shown. Clicking on Continue will resume the plot at that point. You may pause as many times as you like, and a red cone marker will appear at each pause point.

If the plot is happening too quickly, or too slowly, you may pause the plot, change the value in the "Plot Delay" dropdown at the bottom of the control panel, and continue. Please note, however, that the speed at which the plot is drawn is a function of many factors, and we can only influence, not determine, how fast the plot is drawn.

If you wish to cancel the plot, clicking "Clear" will erase the track, and indicate the last point in that track.

Each time you change any of the options, click the Plot button to redraw the track. Please note that each time this is done, both the zoom level and the map center may be reset: The plotting code sets the zoom level and map center so that the entire track may be seen. You may then zoom and drag the map.

Because drawing the plot will sometime be slow, especially IE, when a track is in progress, the 'Select Ship and Options' label at the top of the control panel will change to: "****** WORKING *******" and will blink slowly.

Since some browsers, such as Chrome and Safari, typically draw the track too quickly for it to be easily followed visually, there is a "Plot Delay" control at the bottom of the control panel that allows you to select one of several millisecond period delays that are inserted between each point in the track.

Because of the high frequency with which vessel position is reported, when tracks are plotted (with or without environmental data), plotting every point (as the vessel might not have moved signficantly, if at all) would be very time-consuming and visually confusing. Therefore, the vessel must have moved about 35 meters from one point to the next for the latter point to be used for plotting. If the latter point is too close, it is discarded and the next point is considered.

In addition to the visual display of track (without or without environmental data), you may use the Download button to retrieve the track and data information as an .xls file. Download will return the latitude and longitude of each point in the track, with the current Type of Data, if one is selected.

In the downloaded file, the date and time for each point will be shown, either in GMT or ET, based on the setting of the Time Zone" drop-down. For those parameters for which there are both English and Metric units, the "Units" drop-down will determine the units returned in the file.

If you wish download a file that includes all types of data, click the "Download All" button. Please note that when using "Download All" the Time Zone and Units selections are ignored: the download will use GMT and Metric units.

Davidson Laboratory Mobile Stations
Select Ship and Options
Set Default
  (HH:MM, 24 hour format)
  (HH:MM, 24 hour format)
On some computers and browsers, the track will plot too quickly if allowed to draw as quickly as possible. The default setting (in the dropdown control below) is for a 20ms delay between points. If you would like to change the speed, select a larger number to slow it down, or 'No Delay' to enable maximum rendering speed.