SkewTLogPro vs TruAirspeed

SkewTLogPro gives you one-touch access to powerful skew-t log-p charts. View charts using your current GPS location, airport ID code or lat/lon. Each skew-t log-p chart provides a visual indication of temperature, dew point, winds aloft, and wind speed at various altitudes, as well as Current Radar, Airmets, Sigmets, and SkewT data charted, filtered by altitude. FEATURES: • NEW! View all Sigmet/Airmet on a map and filter by altitude • NEW! View SkewT data charted on a map with altitude filtering, shows potential warnings of Icing, Wind, and Visibility • Ability to view the lifted parcel line • Support for International Airport ICAO codes • View charts along your route using 'View Route' • Support for GFS for all locations outside the continental United States (Option in Settings) • View many values such as CAPE, LI, LCL, and many other options through settings • Save charts for offline use • View Skew T Log soundings by touching a location on a map • View skew-t log(p) charts using your current GPS location, airport identifier or latitude and longitude. • Scroll forward and backward to view past and forecast charts. • History list allows easy access to previously viewed locations. • Select how many previous and forecast hours are charted • Drag on the graph to view each point value • Double-tap to zoom in for more detail on the soundings. • Great for aviators, glider pilots and weather enthusiasts. An annual subscription is required to access these graphs and to use SkewTLogPro for $12.99 per year. Cancel anytime. Please view the End User License Agreement here: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

TruAirspeed is a True Airspeed Calculator for the iPhone and iPad. It's a bit different from other true airspeed calculators, in which the pressure altitude is an input. This requires resetting the altimeter to the standard sea level pressure of 29.92"Hg to read the pressure altitude. With TruAirspeed, you input the indicated altitude and the Kollsman window's pressure setting — the app then calculates the pressure altitude, density altitude, true airspeed and mach number for you. The calculations involved take full account of compressibility effects, but not shock waves, so it's limited to subsonic, non-transonic flight only. You have a choice of units for inputs and results, and you may choose either a calculator-style keypad (top row: 7-8-9) or a telephone-style keypad (top row: 1-2-3). You may also set a correction factor for your bird's airspeed indicator/pitot-static system, if you know it (mine is 0.95).