Wednesday, March 27, 2013

Aviation Forecasts and Current Location

It's time for another SARWeather update report. Many of these changes have already been made available over the last few weeks, and it is now time to tell the world about them.

We have introduced specialised aviation forecasts, show the user's current location on forecast maps and made various interface improvements.


Aviation Forecasts

The most significant change is the inclusion of wind forecasts for aviation. When requesting a forecast, there is a new check box to create an aviation forecast. This will cause the full three-dimensional output of the weather model to be stored, and plots showing wind and turbulence at certain heights to be generated.

Aviation option and cost indicator when requesting forecasts.

Aviation forecasts require much more storage and processing on our servers, so they will cost more than ordinary forecasts. Currently, the cost is set at 4 times the price of the equivalent flat forecast. Because the price structure has become slightly more complex, we now show the price of the forecast right on the confirmation button, so that user's won't accidentally start a more expensive forecast than intended.

Wind and turbulence at 1000 ft above ground level near Mont Blanc.

The coloured surfaces in the aviation wind forecasts are equivalent to those in ground-level wind plots. However, since higher wind-speeds are encountered at higher elevations, we have significantly extended the scale We show a scale up to 100 m/s (97 knots), but there are colours defined up to 150 m/s (291 knots).

The wind barbs are equivalent to those in the combined weather plots, with each full barb signifying 5 m/s (9.7 knots) and flags signifying 25 m/s (48.6 knots).

The scattering of black dots visible on the map indicates turbulence, calculated with the Graphical Turbulence Guidance system. There is a sparse pattern indicating light turbulence, and a tighter pattern indicating medium turbulence, while stars indicate heavy turbulence.

The aviation forecasts show the wind and turbulence at levels determined by the resolution of the forecast. The rule is that higher-resolution forecasts will show lower flight levels, suitable for flying low over complex terrain or selecting landing sites. Lower-resolution forecasts, meanwhile, show higher flight-levels suitable for flying longer distances.

The heights plotted for each resolution are given in the table below, where AGL = Above Ground Level and ASL = Above Sea Level.

1km3km9km
100ft AGL
150ft AGL
250ft AGL
500ft AGL
1000ft AGL
2500ft ASL
5000ft ASL
150ft AGL
500ft AGL
1000ft AGL
2500ft ASL
5000ft ASL
10 000ft ASL
18 000ft ASL
5000ft ASL
10000ft ASL
18000ft ASL
24000ft ASL
30000ft ASL
34000ft ASL
39000ft ASL

Note that all these details are subject to change and we would very much like feed-back from our users to help us adjust them.

Current Location

We now show the user's current location on maps, both when requesting a forecast and viewing the results. On zoomable maps there is a red marker, but on the static maps we use a small red circle. This can be useful when looking at the forecast on a tablet in a moving vehicle or generally in unfamiliar surroundings. On mobile platforms, the location marker will move with the user although this is not intended for navigation.

Red circle showing the user's location on forecast map.

This functionality requires the user to allow SARWeather access to their current location, and depends on the browser having access to useful location information. On mobile platforms, this will often be a GPS receiver, while desktops and laptops will tend to use the network they are connected to for an approximate location.

Other Interface Changes

In the forecast list, we've added two icons to each forecast as appropriate. The magnifying glass indicates that a zoom-able map is available, while the aeroplane icon indicates an aviation forecast.

Aviation and zoom-ability indicators on forecast cards.

We have adjusted the colour scheme used for wind speed so that black overlays are more clearly visible. This involved making the darkest versions of each colour band more distinct from black, generally by using a brighter colour.

A number of smaller improvements have been made throughout the system.

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