The PING data viewer consists of a single basic screen. The initial impression may be one of an overwhelming forrest of controls, but the functionality of all the available options is easy to learn and intended to be as intuitive as possible. Much of the navigation can be ignored if one only seeks a quick look at current reports and nothing one can set on the page is difficult to undo. The figure at the right shows a screen shot of the web viewer with five regions highlighted and labeled (A, B, C,... F). In the sections that follow, there are explanations of all five areas along with some other helpful information.


What is UTC?

First off, it should be noted that all the times used on this page are in UTC. Weather is happening all around the world simultaneously and for over 100 years it has been recognized that using multiple local time zones is a major nuisance for studying a global system. UTC stands for Coordinated Universal Time (the letter order comes from the french phrase). Furthermore, a 24 hr clock style is used instead of designating AM or PM. So in hour:minute format the UTC day runs from 00:00 UTC (midnight) to 23:59 UTC before rolling over to the next midnight and, for instance, 14:30 UTC is the same as 2:30 PM on that UTC day. 14:30 UTC is also the same as 14:30 GMT (Greenwich Mean Time) or 14:30 Z (commonly used in aviation). UTC actually is the local time zone in Iceland and parts of Great Britain.

While foriegn at first, it is not hard to adapt. The UTC time zone is about




way around the earth to the east of the United States and hence about




of a day ahead on the clock. The figure to the right gives the transformation. When it is early evening (6PM) in the central US it is about time for a new UTC day to start.

Upon first loading the page (or refreshing the browser) the default display consists of 6 hrs of reports ending at the currnet time. The current UTC time is also shown in the upper left on the page. In the US this should be anywhere from 4 to 8 hrs later than one's local time.

A.) Controlling the Map Region

The default map covers the entire continental United States but clicking and dragging on the map itself gives the user robust zoom control and the ability to see very fine scale structure. When the mouse is just hovered over the map a text output shows the coordinates of that point as indicated in the figure. Clicking and dragging with the left mouse button will generate a rectangle region. When the mouse button is released, the display will then refresh to the new region. The rectangular region has a fixed aspect ratio and as such it will not track exactly with the mouse pointer. The mouse location will either be setting the width or height of the rectangle, depending on whichever is closer to the allowed ratio. If one simply clicks on the map, then the display will zoom in very close to that spot with a default map size. Once zoomed in, the two zoom out buttons act to return the user to a larger region. Neither has any effect when already at the full region.

Map Thresholds

The default map covers a latitude range of 35 degrees (from 55 N to 20 N). As one zooms in, certain thresholds trigger a change in the map characteristics. Below a 20 degree latitude range the precipitation type symbols become the full size versions as shown on the legend. Crossing the 10 degree latitude range threshold causes county boundaries to appear and at 2 degrees or less urban boundaries and major roads are added.

B.) Selecting Precipitation Types

This corner of the webpage is easy to understand. It acts as a legend for the symbols used to represent the different precipitation types. But it is also a set of selectors to customize what types get displayed. The grey rectangle with the precipitaion type name is an active button. It acts to 'toggle' that type on or off, meaning as you repeatedly click the rectangle the button turns dark grey, then light grey, then dark grey and so on. The default is to have all types on (indicated by light grey). In the figure below 'Test' and 'None' have been turned off and the all the rest are still on. Changes here should take place instantly on the map regardless of other settings. The symbols shown on the legend/selector box are those used when the map is zoomed in past 20 degrees latitude range. For larger maps a more diminutive set of symbols of the same basic design are used, but these can be difficult to fully distinguish.

Hail reports include a diameter. The text inside the white hail circle symbol is this diameter value in 0.25 inch increments. So a '1' means 0.25 inch diameter hail and a 4 would mean 1.0 inch diameter hail. When this value is two digits, the hail circle symbol is slightly larger.

C.) What is 'Show History'?

This button is also a simple toggle. In the animation loop there is an active time window within which data is shown with its full color symbols. Data that is 'older' than that active time window but still within the animation loop bounds is the 'history'. This history can be shown in grey or left out. If the animation is running slower than normal due to the volume of reports, then suppressing the history will increase the speed.

D.) Animation Looping Controls

This navigation area is more complicated. When the page first loads the default display loops a 1 hr window of data moving through the most recent 6 hrs. This situation is shown in the top figure on the right. The dark green and dark red indicators just below the 'Time Strip' set the start and end of the animation looping range. These indicators can be moved via a click and drag with the mouse. However, the end loop indicator can not be dragged into the future (the portion of the Time Strip in black).

The 'Active Window Duration' buttons can alter the width of the data window that is shown in full color. The width of the active window can't be longer than the entire loop range, but the options that would violate this rule will automatically turn grey/deactivate.

The loop speed can be adjusted with the small slider indicated in the figure. Buttons to pause, play forward and play reverse are provided. In addition, if one simply clicks the moving active window (medium blue moving rectangle with the black dot) the loop will pause and then a click and drag can be used to move the active window back and forth at will.

To be able to set the active window to the entire 24 hrs one needs to navigate away from the current day. On a earlier day, the entire Time Strip is available and once the start and end loop indicators are dragged to the two ends, the 24 hr duration button will become available. Note that whenever the active window fills the entire animation loop range that is set, then no looping will be apparent regardless of the pause/play state of the controls. Full 24 hr mode is a useful setting for searching the archive for past events in one's area.

More Soon...

Auto Refresh

To see new reports since the last time the page was loaded, some sort of page refresh needs to occur. This can be accomplished with the browser's refresh button, but all custom settings (zooming in/changing loop speed/hiding certain types) will be lost. The page will be re-entered with all the original defaults, just at the current time. At the other extreme, one can refresh the page by clicking on the current date in the calendar. This keeps all the custom settings. But this includes the loop range as well, so the display doesn't change much. The only change will be the black portion on the time strip indicating the future shrinks to the left. One would still need to manually slide the 'end of loop time marker' to the left to see more recent data. It is not difficult to set a webpage to automatically reload itself on a timer. But the fact this page serves as both a real time monitoring page with many custom settings and as an investigation tool for past archives complicates how one would want that to occur.

For real time monitoring there is an 'Auto Reload' option that can turned on or off by the user. If one is viewing any date in the past, then automatic page refreshes will not occur and the option does not even show. If, however, one is on the current date the option appears. If left 'off', the page will never refresh without a user manaully making that request. If one turns the option 'on', then the page can be left open to act as a continuous monitor. The page will automatically refresh itself every 5 minutes. Note; there are a variety of situations on the users end that can interfere with this behavior such as the browser being minimized, or the PING display being in a background tab, or hibernation of the machine, but when focus is returned to the PING page, the reload timer will resume. An attempt has been made to have this auto-reload perserve as many of the custom settings as would make sense. On the figure above all the options indicated by the green boxes should not change on reload - zoom setting/show history/precip types shown/loop speed/active window duration. The items 'X'-ed out in red will keep resetting each reload; so it will always be a playing loop of the last 6 hrs for the current date. The 'Auto Refresh' button acts as a simple toggle bewteen 'off' and 'on'.