Apple Watch, meet backcountry hiking: How Apple’s smartwatch tracks long-distance exercise
- apr
- 24
- Posted by Michael
- Posted in Okategoriserade
The Series 3 Apple Watch is great for everyday use and exercise tracking. But how does it fare in the backcountry?
Around where I live, the Apple Watch is a hit. I'm often surprised at how many people I see wearing one as I visit clients, or while standing in line at the coffee shop. Smart notifications, custom complications, and fitness tracking have made the watch a compelling product for most everyday tasks, and as of Series 3, the product seems to have at last found its groove.
But I don't spend my free time doing everyday tasks: I prefer to leave the pavement and the daily workout routine behind and head for the mountains. Naturally, it made me curious — could the Series 3 Apple Watch track my backcountry workouts as well as more-normal tasks?
iPhone, watch, or GPS device?
I've been using my iPhone to track workouts and activity for several years now using the popular Strava app. With the app and phone, I get reasonable accurate GPS data for all my runs, including elevation profiles and detailed route tracking.
Last year, I crossed the Grand Canyon on the famous R2R2R trail. I ran from South Rim to North Rim, tracking my run with my iPhone (and taking plenty of pictures along the way). On what ended up being a 19-hour journey, I charged my device mid-run with a little GoalZero battery pack and a three-inch Lightning cable; as such, my iPhone never came close to running out of juice.
Pro tip for running with the iPhone: Dim its screen way down and put your device into Airplane mode to keep your battery lasting as long as possible.
But it's not just smartphones that can track your runs: Many ultrarunners (ultra = traveling extra-long distances, usually 42k or more) use Garmin or Suunto watches to track runs and athletic progress.
A few months ago, I joined that club and bought myself a Suunto Spartan Sport Wrist HR GPS watch. Its $499 price is pretty standard for for ultrarunning and backcountry exploring trackers, though the watch is a monster in size on your wrist.
At this price, Suunto also has a lot of comparable features to the Series 3 Apple Watch: While higher-end trackers have additional sensors like barometers and altimeters that can offer more accurate elevation tracking, they're also closer to the $700-$900 range; most watches for GPS-tracking come in closer to $300-$500, right in line with a base-model Series 3 Apple Watch.
At this point, I felt comfortable with my Suunto and iPhone, so I had a good baseline to test against my 38mm Series 3 Apple Watch.
For my primary test, the plan was to take both watches out into the wilderness — deep into Olympic National Park in Washington state. There's no cell service — only rugged terrain, high mountains, old trees and, as luck would have it, a sunny (but cold) day. I also tracked over a dozen training runs with both watches, so as to get multiple data points.
I had three categories I was most interested in comparing:
- General ease of use: How does the Apple Watch fit into the lifestyle of a backcountry trail runner?
- Battery life: How long can I stay in the backcountry and have the Apple Watch reliably track my location?
- GPS accuracy: Does the Apple Watch accurately track my activity, run length, and where I am on the trail? This isn't just a vanity metric: If I get lost in the backcountry, a reliable GPS signal allows me to stay safe and get back to familiar grounds.
This was, admittedly, narrow criteria: Both of these watch options can do a lot more, especially the Apple Watch.
But in the backcountry — far away from cell service that you don't need — you shouldn't be too concerned about bill reminders, summoning Siri, reading texts, or streaming music. (And without a signal, you're out of luck for most of those features, anyway.) Additionally, by reducing the number of actions you perform on your Apple Watch, you can keep your battery lasting much longer than if you were trying to send a message during your run.
How the Apple Watch fares against the Suunto Sport
After several months of testing these watches head to head, it's often felt like I'm comparing a Jeep to a BMW. (You guess which one is which.) A BMW can win in most every daily driving situation, yes. But there are a few occasions where you'd only want to take a Jeep. Backcountry running? That may well be one of those situations. But as I came to discover, the Jeep wasn't always the right tool, either.
During my tests, I set out with both watches in Airplane mode, with external signals disabled. I recorded my run in Strava on the Apple Watch, while I used the onboard activity app for the Suunto.
General ease of use
Let's start with general wear. On the wrist, the Apple Watch feels great: It's much easier to pull jacket sleeves up and down over its 38mm size than the Suunto. I expected some fatigue from consistently wearing devices around my wrist, but after 5+ hours I didn't mind either of the watches.
Both watches charge via their respective proprietary USB connector cable, which connect to the rear sensor area of the watch. Unfortunately, this means mid-activity charging is impossible for either device — which, quite frankly, sucks when you're on the trail for long distances.
Additionally, the Apple Watch charger, while slick and beautiful on a bedside table, is useless if you want to charge your watch in the car on the way to the trailhead. The magnetic connection is way too flimsy and can all too easily disconnect while driving. In contrast, Suunto's connector is stronger: The magnet connects with more heft and can handle a lot of jiggling around in the car before it disconnects.
During a run, the delay of the Apple Watch's 'raise to wake' view is ever so slightly annoying; the Suunto's always-on screen is better for quick glances at your progress as you run.
I also wish I could lock the screen of the Apple Watch to one app. Sometimes, mid-run, I felt there was too much going on on that tiny screen. All I want is a big button to track my run and some numbers to show my progress.
One thing I thought would be a big plus for the Apple Watch was the ability to natively use the Strava app to track my run. But in my testing, it wasn't so great: I lost a run completely, and syncing sometimes required a bit of extra help, especially after the watch was in Airplane mode and away from the phone.
Suunto has its own app, Movescount. This app lets you transfer the data from the Spartan watch over to a website. There, you can see a whole bunch more information and sync your activity to Strava. The intermediary step is annoying, but the Movescount app actually offers additional data points, like Cadence tracking, suggested recovery time, and a few other things I found quite helpful.
One funny note: In two months of testing, I only once closed all my Activity Rings — and it wasn't even on a big backcountry day. (The truth is, after you come back from a long day out, sweaty and exhausted, the first thing you're going to do is take off your watch and recharge it. Goodbye, stand goal.)
GPS tests
Both the Apple Watch and Suunto Spartan performed surprisingly similar in my GPS tests during my main trail run.
- The Apple Watch tracked my backcountry run at 20.11miles, while Suunto came in at 20.14miles.
- Elevation gain for Apple Watch was 1222ft, while the Suunto Spartan put it at 1353ft. This is on par with the official numbers for this trail, and the deviation is acceptable.
On subsequent training runs, I was pretty pleased with the Apple Watch's GPS performance. It even pulled ahead of Suunto in some respects — especially elevation accuracy.
Battery
Battery life was an eye-opener: I started my run with both watches fully charged, but after five hours of activity, the Apple Watch was down to 15%, while the Suunto still had 40% juice left. I did test these watches during winter in the Pacific Northwest, and the cold temperatures might have had an affect on battery performance. (It was 32 degrees on my backcountry run with frost on the ground in places).
And I had both watches continuously track my heart rate throughout, which is something you can disable to extend battery life. That said, on a different run with heart rate tracking turned off, I still lost about 15% battery life after an hour of Strava tracking.
The size of the Apple Watch is worth considering, too: I ran with the smaller 38mm size, which historically has a tinier battery and poorer overall battery life than its 42mm cousin.
But given that I was already in Airplane mode, this number doesn't bode well for using Apple Watch to track any activity longer than 6-8 hours.
The ultimate backcountry tool is still out there
I was really hoping the Apple Watch could be an ultimate backcountry tool, but neither it nor my Suunto watch truly delivers right now: I wouldn't trust a watch as the only device I take with me into the wilderness. Their limited battery life, tiny screens, and inability to recharge throughout the run left me a bit lackluster. While both wearables have their perks, I had hoped for more from a smartwatch in 2018.
Both watches are a great additions to your backcountry toolkit, but neither are the end-all solution. The Apple Watch is like a little coupe sports car. It's lightweight, delightful to use, and fun, but it's also a bit finicky with too many dials and a small gas tank.
The Suunto Spartan, in contrast, is so big and bulky that you'd only want to wear it for your runs. It's aimed for one purpose only — to track your activity — and it does. But even it has its drawbacks.
My true discovery: I still love my iPhone
After about two months of testing, I came to the realization that even if my watches weren't the panacea I was looking for, I already have a great backcountry tool: my iPhone.
It can recharge mid-flight, a key problem that no smartwatch can really handle effectively. It has a large screen and powerful mapping apps, both of which are much better ways to navigate through the woods.
On backcountry outings, you need to bring a backpack with essential gear, and a phone and charger won't add much to your weight. And, of course: You need to phone to take pictures of your trip.
I was looking forward to wearing a watch again all day, and there is something nice about getting that quick glance at your progress — something a smartphone can't provide. But as much as I like aspects of the Apple Watch, it's not yet the perfect backcountry tool for me. Maybe next year. Until then, I'll keep running with my iPhone.
Senaste inläggen
- Så tar du bort föreslagna kontakter från Iphones delningsmeny
- Influencer preps for Apple Pencil 3 by destroying 45 Apple Pencils in viral ’How many can hold me’ TikTok video
- Netflix ditching its Basic tier forces people to endure ads or pay more and shines a spotlight on Apple TV Plus’ undeniable value
- Apple received a whopping $20 billion to make Google the default iPhone search engine in 2022, damning antitrust documents prove
- Dough Spectrum Black 27-inch OLED monitor is more ‘d’oh’ than ‘woah’, but rich screen tech helps make the steep price tag more palatable
Senaste kommentarer
Arkiv
- maj 2024
- april 2024
- mars 2024
- februari 2024
- januari 2024
- december 2023
- november 2023
- oktober 2023
- september 2023
- augusti 2023
- juli 2023
- juni 2023
- maj 2023
- april 2023
- mars 2023
- februari 2023
- januari 2023
- december 2022
- november 2022
- oktober 2022
- september 2022
- augusti 2022
- juli 2022
- juni 2022
- maj 2022
- april 2022
- mars 2022
- februari 2022
- april 2021
- mars 2021
- januari 2021
- december 2020
- november 2020
- oktober 2020
- september 2020
- augusti 2020
- juli 2020
- juni 2020
- maj 2020
- april 2020
- mars 2020
- februari 2020
- januari 2020
- december 2019
- november 2019
- oktober 2019
- september 2019
- augusti 2019
- juli 2019
- juni 2019
- maj 2019
- april 2019
- mars 2019
- februari 2019
- januari 2019
- december 2018
- november 2018
- oktober 2018
- september 2018
- augusti 2018
- juli 2018
- juni 2018
- maj 2018
- april 2018
- mars 2018
- februari 2018
- januari 2018
- december 2017
- november 2017
- oktober 2017
- september 2017
- augusti 2017
- juli 2017
- juni 2017
- maj 2017
- april 2017
- mars 2017
- februari 2017
- januari 2017
- december 2016
- november 2016
- oktober 2016
- september 2016
- augusti 2016
- juli 2016
- juni 2016
- maj 2016
- april 2016
- mars 2016
- februari 2016
- januari 2016
- december 2015
- november 2015
- oktober 2015
- september 2015
- augusti 2015
- juli 2015
- juni 2015
- maj 2015
- april 2015
- mars 2015
- februari 2015
- januari 2015
- december 2014
- november 2014
- oktober 2014
- september 2014
- augusti 2014
- juli 2014
- juni 2014
- maj 2014
- april 2014
- mars 2014
- februari 2014
- januari 2014
Kategorier
- –> Publicera på PFA löp
- (PRODUCT) RED
- 2015
- 25PP
- 2nd gen
- 32gb
- 3D Touch
- 3D-kamera
- 4k
- 64gb
- 9to5mac
- A10
- A9X
- Aaron Sorkin
- Accessories
- adapter
- AirPlay
- AirPods
- Aktiv
- Aktivitetsarmband
- Aktuellt
- Alfred
- AMOLED
- Android Wear
- Angela Ahrendts
- Ångerätt
- announcements
- Ansiktsigenkänning
- app
- App Store
- Appar
- Apple
- Apple Beta Software Program
- Apple Book
- Apple CarPlay
- Apple Event
- Apple iMac
- Apple Mac Mini
- Apple Macbook
- Apple MacBook Air
- Apple MacBook Pro
- Apple Macos
- Apple Maps
- Apple Music
- Apple Music Festival
- Apple Music Radio
- Apple Offer
- Apple Online Store
- Apple Park
- Apple Pay
- Apple Pencil
- Apple Podcast
- Apple Store
- Apple Store 3.3
- Apple TV
- apple tv 4
- Apple TV 4K
- Apple Watch
- Apple Watch 2
- Apple Watch 8
- Apple Watch 9
- Apple Watch Apps
- Apple Watch SE
- Apple Watch Series 2
- Apple Watch Sport
- Apple Watch Ultra
- AppleCare
- AppleTV
- Application
- Applications
- Apps
- AppStore
- Apptillägg
- Apptips
- AppTV
- April
- Arbetsminne
- armband
- Art Apps
- Återköp
- återvinning
- Åtgärdsalternativ
- atvflash
- Audio Apps
- Augmented REality
- Back-to-school
- Bakgrundsbilder
- BankId
- Barn
- Batteri
- batteriskal
- batteritid
- Beats
- Beats 1
- Beats Solo 2 Wireless
- Beats Solo2
- Bebis
- Beginner Tips
- Belkin
- Bendgate
- beta
- Beta 3
- betaversion
- betaversioner
- bilddagboken.se
- bilder
- bilhållare
- billboard
- Bioteknik
- Blendtec
- Bloomberg
- Bloons TD 5
- Bluelounge
- Bluetooth
- Böj
- Booking.com
- Borderlinx
- bose
- bugg
- Buggar
- Buggfixar
- Butik
- C More
- Calc 2M
- Camera
- Campus 2
- Canal Digital
- Carpool Karaoke
- Caseual
- Catalyst
- CES 2015
- Chassit
- Chip
- Chrome Remote Desktop
- Chromecast
- citrix
- clic 360
- CNBC
- Connect
- Cydia
- Dagens app
- Dagens tips
- Damm
- Danny Boyle
- Data
- datamängd
- Datorer
- Datortillbehör
- Datum
- Defense
- Dekaler
- Designed by Apple in California
- Developer
- Development
- Digital Inn
- Digital Touch
- Digitalbox
- DigiTimes
- Direkt
- Discover
- display
- DisplayMate
- Dive
- Docka
- Dräger 3000
- Dropbox
- Droples
- DxOMark
- E-post
- earpod
- EarPods
- Earth Day
- Eddie Cue
- eddy cue
- Educational Apps
- Ekonomi
- Ekonomi/Bransch
- El Capitan
- Elements
- ElevationLab
- Elgato Eve
- Elgato Eve Energy
- EM 2016
- Emoji
- emojis
- emoticons
- Enligt
- EU
- event
- Eventrykten
- EverythingApplePro
- Faceshift
- facetime
- Fäste
- Featured
- Features
- Feng
- Film / Tv-serier
- Filmer
- Filstorlek
- Finance Apps
- Finder For AirPods
- Finland
- FireCore
- Fitbit
- Fitness Accessories
- Fjärrstyr
- Flurry
- Födelsedag
- fodral
- Förboka
- Force Touch
- förhandsboka
- Första intryck
- Forumtipset
- foto
- FoU (Forskning och Utveckling)
- Fource Touch
- Foxconn
- FPS Games
- Framtid
- Fre Power
- Frontpage
- Fullt
- Fuse Chicken
- Fyra
- Gadgets
- Gagatsvart
- Gamereactor
- Games
- Gaming
- Gaming Chairs
- Gästkrönika
- General
- Gigaset
- Gitarr
- Glas
- GM
- Google Maps
- Google Now
- gratis
- grattis
- Guide
- Guider
- Guider & listor
- Guld
- hack
- Halebop
- hållare
- Hälsa
- Hårdvara
- HBO
- HBO Nordic
- Health
- Health and Fitness
- Health and Fitness Apps
- Hej Siri
- Helvetica Neue
- Hemelektronik
- Hemknapp
- Hemlarm
- Hermes
- Hitta min iphone
- Hjärta
- högtalare
- HomeKit
- HomePod
- hörlurar
- htc
- Hue
- Humor
- i
- I Am A Witness
- IBM
- iBolt
- iBomber
- iBook
- icar
- iCloud
- iCloud Drive
- iCloud Voicemail
- iCloud.com
- iDevices
- IDG Play
- idownloadblog
- iFixit
- ikea
- iKörkort
- iLife
- Illusion Labs
- iMac
- IMAP
- iMessage
- iMessages
- iMore Show
- Incipio
- InFuse
- Inspelning
- Instagram-flöde
- Instrument
- Intel
- Internet/Webbtjänster
- iOS
- iOS 10
- iOS 12
- iOS 17
- iOS 18
- iOS 5
- iOS 7
- iOS 8
- iOS 8 beta
- iOS 8.1.3
- iOS 8.2
- iOS 8.3
- iOS 8.4
- iOS 8.4.1
- iOS 9
- iOS 9 beta 4
- iOS 9.1
- iOS 9.1 beta 2
- iOS 9.2
- iOS 9.2.1
- iOS 9.3
- IOS Games
- ios uppdatering
- ios9
- iPad
- iPad Accessories
- iPad Air
- iPad Air 2
- iPad Air 3
- iPad Apps
- iPad Mini
- iPad mini 4
- iPad Mini 6
- iPad mini retina
- iPad Pro
- iPados
- iphone
- iPhone 12
- iPhone 14
- iPhone 14 Pro
- iPhone 15
- iPhone 16
- iPhone 17
- iPhone 5
- iPhone 5S
- iPhone 5se
- iPhone 6
- iphone 6 plus
- iPhone 6c
- iPhone 6s
- iPhone 6S plus
- iPhone 7
- iPhone 7 display
- iPhone 7 Plus
- iPhone 7s
- iPhone Accessories
- iPhone Apps
- iPhone SE
- iphone x
- iPhone XS
- iPhone XS Max
- iPhone7
- iPhoneGuiden
- iPhoneguiden.se
- iPhones
- iPod
- iPod Nano
- iPod shuffle
- ipod touch
- iSight
- iTunes
- iWatch
- iWork
- iWork för iCloud beta
- Jailbreak
- James Corden
- Jämförande test
- Jämförelse
- Jet Black
- Jet White
- Jönssonligan
- Jony Ive
- Juice Pack
- Juridik
- Just mobile
- kalender
- kalkylator
- Kamera
- Kameratest
- Karriär/Utbildning
- Kartor
- Kevin Hart
- keynote
- Keynote 2016
- KGI
- KGI Security
- Kina
- Klassiskt läderspänne
- Kod
- Kollage
- koncept
- konceptbilder
- köpguide
- krasch
- Krascha iPhone
- Krönika
- Kvartalsrapport
- Laddhållare
- laddningsdocka
- Laddunderlägg
- läderloop
- lagar
- Lagring
- Lajka
- Länder
- lansering
- laserfokus
- Layout
- leather loop
- LG
- Liam
- Lifeproof
- Lightnigport
- lightning
- Linux
- LinX
- live
- Live GIF
- Live Photos
- Live-event
- Livsstil
- Ljud & Bild
- Logitech
- LOL
- Lösenkod
- Lösenkodlås
- Lovande spel
- LTE
- Luxe Edition
- M3
- M3TV
- Mac
- Mac App Store
- Mac Apps
- Mac Mini
- Mac OS
- Mac OS X
- Mac OS X (generellt)
- Mac OS X Snow Leopard
- Mac Pro
- Macbook
- Macbook Air
- Macbook Pro
- Macforum
- Macintosh
- macOS
- Macs
- MacWorld
- Made for Apple Watch
- magi
- Magic
- MagSafe
- Martin Hajek
- matematik
- Meddelanden
- Media Markt
- Medieproduktion
- Mediocre
- Messaging Apps
- Messenger
- MetaWatch
- Mfi
- Michael Fassbender
- microsoft
- Mikrofon
- Minecraft
- Ming-Chi Kuo
- miniräknare
- minne
- Mixer
- Mixning
- Mjukvara
- mobbning
- Mobile Content
- Mobilt
- Mobilt/Handdator/Laptop
- Mobiltelefon
- Mockup
- Mophie
- mors dag
- moto 360
- Motor
- MTV VMA
- multitasking
- Music
- Music Apps
- Music, Movies and TV
- Musik
- Musikmemon
- MW Expo 2008
- native union
- Nätverk
- Navigation Apps
- nedgradera
- Netatmo Welcome
- Netflix
- Netgear Arlo
- News
- Niantic
- Nike
- Nikkei
- Nintendo
- Nöje
- Norge
- Notis
- Notiscenter
- nya färger
- Nyfödd
- Nyheter
- Officeprogram
- Okategoriserade
- OLED
- omdöme
- Omsättning
- OS X
- OS X El Capitan
- OS X Mavericks
- OS X Yosemite
- Outlook
- Övrig mjukvara
- Övrigt
- PanGu
- papper
- patent
- PC
- pebble
- Pebble Smartwatch
- Pebble Steel
- Pebble Time
- Pebble Time Steel
- Persondatorer
- Petter Hegevall
- PewDiePie
- Philips
- Philips Hue
- Phones
- Photoshop
- Planet of the apps
- Plex
- Pluggar
- Plus
- Plusbox
- Podcast
- Podcast Apps
- Policy
- Porträttläge
- PP
- Pris
- priser
- problem
- Problems
- Productivity Apps
- Program
- Prylar & tillbehör
- Publik
- publik beta
- QuickTime
- räkenskapsår
- räkna
- ram
- RAM-minne
- Rapport/Undersökning/Trend
- Rea
- Reading Apps
- recension
- Red
- reklaamfilm
- reklam
- reklamfilm
- reklamfilmer
- rekord
- Rendering
- reparation
- Reportage
- Reptest
- ResearchKit
- Retro
- Review
- Ring
- Ringa
- Rocket Cars
- Rosa
- Rumors
- Rumours
- RunKeeper
- rykte
- Rykten
- Safir
- Säkerhet
- Säkerhetsbrist
- Samhälle/Politik
- samsung
- Samtal
- San Francisco
- SAP
- security
- Series 2
- Servrar
- Shigeru Miyamoto
- Sia
- Siri
- SJ Min resa
- skal
- Skal iPhone 6
- skal iPhone 6s
- skärm
- SKärmdump
- Skärmglas
- Skribent
- skribenter medarbetare
- Skriva ut
- skruvmejsel
- skydd
- Skyddsfilm
- Skype
- slice intelligence
- Smart
- smart hem
- Smart Home
- Smart Keyboard
- Smart klocka
- Smart Lights
- smartphone
- Smartwatch
- Snabbt
- Snapchat
- Social Apps
- Software
- Solo2
- sommar
- Sonos
- Sony
- soundtouch
- Space Marshals
- spår
- Speakers
- Special Event
- Spel
- Spelkonsol
- Spellistor
- Split Screen
- Split View
- Sport
- Sportband
- Sports Apps
- spotify
- Spring forward
- Statistik
- Steve Jobs
- Stickers
- Stockholm
- Stor iPhone
- Storlek
- Story Mode
- Strategy Games
- streama
- Streaming
- stresstest
- Ström
- Studentrabatt
- stylus
- Super Mario Run
- support
- Surf
- Surfplatta
- svenska
- sverige
- Sverigelansering
- Switch
- Systemstatus
- Systemutveckling
- tåg
- Taig
- Tangentbord
- Taptic Engine
- Tårta
- tät
- Tävling
- Taylor Swift
- Teknik
- tele 2
- Telefoner
- Telekom
- Telia
- Test
- Tid
- TikTok
- Tile
- tillbehör
- Tim Cook
- TIME
- TimeStand
- Tiny Umbrella
- Tips
- Toppnyhet IDG.se
- Touch ID
- TouchID
- tower defence
- trådlös laddning
- Trådlösa hörlurar
- trådlöst
- trailer
- Travel Apps
- Tre
- TrendForce
- TripAdvisor
- Trolleri
- trump
- TSMC
- Tum
- tv
- tvätta
- tvOS
- tvOS 9.2
- tvOS beta 2
- Tweak
- Typsnitt
- Ubytesprogram
- UE MegaBoom
- Unboxing
- Underhållning/Spel
- unidays
- United Daily News
- Unix
- Updates
- Uppdatera
- uppdatering
- Upplösning
- upptäckt
- USA
- Ut på Twitter
- utbyte
- utbytesprogram
- Utilities Apps
- Utlottning
- utrymme
- utvecklare
- varumärke
- Vatten
- Vattentålig
- vattentät
- vävt nylon
- Verktyg
- Viaplay
- Vibrator
- video
- Videoartiklar och webb-tv (M3/TW/CS)
- Villkor
- viloknapp
- Virtual Reality
- Virus
- visa
- Vision Pro
- VLC
- Volvo on call
- W1
- Waitrose
- Watch OS
- WatchOS
- WatchOS 2
- watchOS 2.0.1
- watchOS 2.2
- Webbtv (AppTV)
- wi-fi
- Wifi-samtal
- Windows
- Windows 8
- WWDC
- WWDC2015
- yalu
- Youtube
- Zlatan