Outernet for Aviation (METARs and TAFs)


#1

Hi from Spain.

I find all this project highly interesting.

As the Weather App has been released, I have thought that it could be interesting to implement more functions related to aviation.

I am talking about METARs and TAFs.

A METAR is a short coded text that gives information about the current meteorological conditions at an airport. They are issued in a 30 minutes interval.

A TAFOR is also a coded text, but in this case is a prediction of the weather at an airport that lasts from 9h to 24h. They are issued in different times intervals depending on the country (normally 6 hours).

At Internet you can find various guides in different languages to decode the messages.

This is an example of a METAR from Turin, Italy airport.

Raw: LIMF 222350Z 04002KT 2000 R36/1400D RA BR SCT018 BKN045 10/10 Q1021

Decoded: Wind 040° 2kt. Visibility 2000m. RVR runway 36 1400m with aggravation. Rain. Mist. Clouds scattered 1800ft, broken 4500ft. Temperature 10°C, dew point 10°C. QNH 1021hPa.

In Windyty, for example, if you select the “Airport” option, you can see these data for different airports.
Example with Turin Airport at Windyty: www. windytv.com/LIMF?45.201,7.073,9
(Sorry, I only can put 2 links in a post because I am new)

You can use this information on ground, for flight planning; or in flight, to anticipate the conditions before you arrive at an airport (for example, you can look at the meteorological information in advance and decide to divert to an alternate airport).

This can be very useful for general aviation. Large comercial planes have data-link from satellites or ground stations to obtain this information. But small planes do not have access to this technology (in US you have a system called ADS-B that can provide you weather information, but it is not implemented on other countries).
Some little airfields are isolated, and sometimes they do not have Internet access, so it would be interesting to obtain this information from Outernet.
In fact, if you are able to point the antenna correctly, you will be also able to obtain this information in flight.

Not all airports have metar or taf data, but if your destination is near to an airport that has it, you can imagine that weather will be similar.

As they are text messages, they can be send as text files (.txt), that do not weigh too much. So, it will not be very difficult to implement.
The Cons are that they must be updated each 30 min to provide reliable information. This can be a bit complex if the process is not automated.

You can get the data for all countries in txt format from this web, for example.

METARs

TAFs

These are the current METARs for all United States:
www. ogimet.com/ultimos_metars2.php?lang=en&estado=United+S&fmt=txt&iord=yes&Send=Send

What do you think about it?

Thanks for your attention. Regards!!!

PD: Sorry for my English.


#2

Can you provide a global feed of this information?


#3

Sorry for not replying before. I have been endeavouring to find the global official feed.

I have finally found the source from NOAA.

SOURCE: Global Metars

You just have to select the “text file” that corresponds to the current UTC hour.

For example, if it is 21:37h UTC, just select the “21z.txt” file. 21Z.txt

The file weighs about 2,5MB. Is it too big for the Outernet?

In fact, there is lot of weather information on this directory.

Regards!


#4

2.5MB is really big, but it appears to be composed of lots of smaller files. How often does the 2.5MB get updated?


#5

Each hour they create a 2.5MB text file. The file from the previous hour can be disregarded, because you only need the current one.

As they create 24 files a day (one for each hour), this will be 60MB a day (there are lots of airports in the world).

If Outernet only transmits 10MB a day, this is really far too much. In this case, I do not see that this can be viable right now.

Maybe in the future, but I am afraid that nowadays it requires too much resources.


#6

I have tried to compress it, and it only weighs 185KB as a “.rar” file (330KB as a “.zip”).

This is much more less than the uncompressed one. As a compressed file, it will be 4,5MB a day.