README.md

This Telegram bot provides a METAR and TAF aviation weather subscription service and weather based tools for flight planing, supplementing official briefing sources.

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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

THIS SOFTWARE IS NOT AN OFFICIAL BRIEFING SOURCE. ANY DATA SENT MIGHT BE WRONG, OUT OF DATE OR OTHERWISE UNUSABLE OR MISLEADING, NO GUARANTEES CAN BE MADE ABOUT THE AVAILABILITY OF THIS SERVICE, ESPECIALLY THE POLLING/SUBSCRIPTION MECHANISM USE PURELY AT YOUR OWN RISK!

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Using the Bot

AviatorsBot is available on Telegram under the name: @AviatorsBot

Sending /help provides a list of all available commands and /help <command> will show you how to use the command.

Features

METAR and TAF Subscriptions

Using this bots subscription service you will receive an update once a new METAR or TAF is published until your subscription expires.

Managing these subscriptions is very straight forward, user friendly and analogous to a unix command line tool. Using /add <ICAO> you can subscribe to one or more stations. /ls lists the stations you are subscribed to and /rm will let you unsubscribe from a station.

Crosswind Calculation

Sending the command /xwind <ICAO> to the bot will provide you with the crosswind and headwind for all runways of that airport.

Density Altitude Calculation

Using the /da <ICAO> command the current density altitude is calculated.

This calculation is based upon the altimeter setting, elevation, temperature and dew point. All of these data points are taken from the METAR and require no further user input.

Calculating the density altitude with consideration for the actual pressure and water vapor pressure results in a more accurate result than just using the elevation and temperature.

If the stations METAR doesn't contain an altimeter setting the METARs for the airfields within 50km of the station will also be retrieved and the altimeter setting of the closest field with a valid value is used.

Current Weather

The /wx <ICAO> command returns the current METAR and TAF and enhances the METAR with an icon for the flight category provided by the aviationweather.gov API.

Worldwide

If possible all commands provide information for the whole world. Using the /region command you can set your default region so that you don't have to provide your region with each command.

Lightning strikes

Maps of lightning strikes can be viewed using the /strikes command.

SIGMET and Flight Conditions Map

Using /sigmet a map of the current SIGMETs and flight conditions, as published in the METARs can be requested. This map is drawn by a dedicated micro service.

After the map is received the user can request the SIGMETs drawn on the map by sending /sigmet <number_on_map>.

Command Shortcuts

For easier typing on mobile phones you can also omit the '/' prefix. For Example both /help and just sending help work.

Technical

System Architecture Overview

MongoDB is used as the persistence backend. Weather updates are retrieved from the aviationweather.gov/NOAA ADDS Textserver in XML format. Crosswind calculations are based upon the airfield and runway information in the openAIP database.

Technology Stack

AviatorsBot is written in Scala using akka for non-blocking IO.

MongoDB is used as the backend. Accessed using the reactive-mongo Scala library for extending the non-block and reactive concept also to this part.

Continuous Deployment

Using a Amazon AWS CodePipeline the bot is continuously deployed to an EC2 instance.

Code is stored in AWS CodeCommit, built with AWS CodeBuild and deployed to the EC2 instance as a Debian dpkg package using AWS CodeDeploy if the build as well as all unit and integration tests succeed.

Production Ready, High Code Quality

The codebase has highly relevant unit and integration tests and a high coverage written mostly using ScalaTests FunSuite which doubles as a specification of the bots feature set and error handling strategies.

To enable seamless testing a macro based DI library is used for Inversion of Control.

Scheduling of Subscription Updates

Quartz scheduler is used to provide reliable and fault tolerant scheduling of weather updates.

For the purpose of immediate retries a RetriableException has been implemented which will cause an immediate refiring of the scheduler up to the number of maximum retries.

Logging and Metrics

Extensive logging and configurability add to the production readiness of the bot.

All commands, messages received and sent and many errors are also monitored and timed using dropwizard metrics for scala.

METAR and TAF Change Detection

METARs and TAFs are considered changed if the MurmurHash3 of the raw text changes or for METARs the observation time and for TAFs the issue time.

This means that the user will get an update if either the issuance time changes or the content.

MurmurHash3 is used because a cryptographic hash function is not necessary for this application. It generates only a 32bit hash which requires for less storage space is fast and available in the scala standard libraries.