An Android Based Mobile Heat Stress App

1. US Army Research, Development& EngineeringCommand An Android Based Mobile Heat Stress App David Sauter Atmospheric Modeling Applications Branch Battlefield Environment Division Army Research Laboratory, WSMR, NM WIDA Conference - Mar 2012 david.sauter@us.army.mil 575-678-2078 [DSN 258-]

2. An Android Based Mobile Heat Stress App Outline • Background • Hot Environment Assessment Tool (HEAT) Overview • Inputs/Output • Validation Status • Summary

3. Background (1 of 2) • Warfighter Impacts: • Annual average of ~200 Army hospitalizations and 2 deaths due to heat stress* • Individuals are more susceptible to heat stress after a heat stress incident • Potential for degraded training and mission execution • Issues: • Heat stress guidance not always available, especially at lower echelons • Heat stress guidance generally based on Wet Bulb Globe Temperature (WBGT) measurements which require bulky instrumentation for accurate readings http://www.skcinc.com/product_images2/755-56791.JPG *Carter, et al. Epidemiology of Hospitalizations and Deaths from Heat Illness in Soldiers. Medicine and Science in Sports and Exercise 2005, 37 (8), 1338–1344.

4. Background (2 of 2) • Solution: • Implement heat stress guidance on a variety of mobile computing devices using look up tables (based on the WBGT) from a Joint Air Force/Army document* • Require only simple readily available meteorological (e.g., via a handheld weather sensor), work rate and clothing configuration inputs • Eliminate WBGT instrumentation dependency http://www.brighthand.com/assets/9093.jpg * Headquarters, Department of the Army and Air Force. Heat Stress Control and Heat Casualty Management. Technical Bulletin 507, Air Force Pamphlet 48-154(I); Headquarters, Department of the Army and Air Force: Washington, D.C., 2003.

5. Hot Environment Assessment Tool (HEAT) Overview • Available on Personal Digital Assistant (PDA), Apple iPhone/iPod Touch andAndroid smartphone and tablet devices • WBGT is computed via a physics based approach* • Simple weather inputs from handheld weather sensor or other readily available source • Cloud amount and type entry from visual observation • Estimate the attenuated solar insolation for the location, date and time (required to compute the globe temperature in the WBGT)** • Display heat stress guidance in terms of work/rest cycle, maximum continuous work time and required hourly water intake • Java implementation under the Android operating systems makes it relatively easy to port from one device (e.g., smartphone) to another (e.g., tablet) • Android version was recently evaluated by a Special Operations Team – formal report to ARL shortly * Liljegren, et.al. Modeling the Wet Bulb Globe Temperature Using Standard Meteorological Measurements. Journal of Occupational and Environmental Hygiene2008, 645−655. ** Shapiro, Ralph. Solar Radiative Flux Calculations From Standard Surface Meteorological Observations, Air Force Geophysics Laboratory, AFGL-TR-82-0039, 1982.

6. Inputs (1 of 3) • SITE tab: • Latitude, longitude, date and time required to compute solar position • If a GPS capability on the device, can automatically assign default latitude and longitude values • Set default date and time values from the system values • Latitude and longitude values range checked (as are all numeric inputs in the app)

7. Inputs (2 of 3) • MET (“Meteorological”) tab: • Values currently manually entered • Kestrel handheld weather sensor used in a recent Special Ops team evaluation • Bluetooth connection on the mobile device and weather sensor should allow for automated ingest of values except for cloud info

8. Inputs (3 of 3) • WORK tab: • “Spinner” (drop down menu) for selecting (standard) clothing and work choices • Qualitative descriptions (in military terms) of each of the work levels • Allows for quick “what-if” calculations to see results for different work and clothing choices • May be able to add additional work and clothing choices in a future release

9. Output (1 of 2) • RSLTS (“Results”) tab: • Work/Rest Cycle (based on 60 minute period) in minutes • Continuous “one time” work duration time after which Soldiers must be given an extended recovery time, preferably in the shade • Water intake requirement provided for both work/rest cycle and continuous work times • May be able to add additional work and clothing choices in a future release

10. Output (2 of 2) • INFO tab: • Information on app version and developer point of contact

11. Validation Status • Guidance from Joint pub lookup tables related to weather is essentially a function of the WBGT, thus need to ensure the WBGT prediction is accurate! • United Kingdom Meteorological Office (UKMO) has provided ARL with results from a WBGT measurement study for 4 geographic locations • A validation version of HEAT was developed to display the 2 calculated WBGT components – natural wet bulb (Tw) & globe temperature (Tg) – as well as the WBGT • WBGT, Tw, and Tg will be compared to the UKMO measured values • To date, 50+comparisons have been completed • All but 2WBGT predictions are within 1 deg C of UKMO measured value Preliminary results are encouraging, however, will need to perform many more evaluations to be statistically significant!

12. Summary • Mobile versions of HEAT can provide critical heat stress guidance at lower echelons and in training environments • The WBGT computation eliminates the requirement for costly WBGT instrumentation • A recent Special Ops team evaluation will hopefully provide useful feedback • WBGT statistical evaluation to be completed in 2012 • HEAT will be made available to the military pending outcome of the WBGT evaluation