An Android Based Mobile Heat Stress App

1 Approved For Public Release; Distribution Unlimited

Approved For Public Release; Distribution Unlimited

An Android Based Mobile Heat Stress App

David SauterAtmospheric Modeling Applications BranchBattlefield Environment DivisionArmy Research Laboratory, WSMR, NM

[email protected] [DSN 258-]

WIDA Conference - Mar 2012

US Army Research, Development & Engineering Command

mailto:[email protected]



• Background• Hot Environment Assessment Tool

(HEAT) Overview• Inputs/Output • Validation Status• Summary

Outline

An Android Based Mobile Heat Stress App



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

* 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.

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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



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

* 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.

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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 Hygiene 2008, 645−655.** Shapiro, Ralph. Solar Radiative Flux Calculations From Standard Surface Meteorological Observations, Air Force Geophysics Laboratory, AFGL-TR-82-0039, 1982.



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)



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



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



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



Output (2 of 2)

INFO tab: • Information on app version and

developer point of contact



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 2 WBGT predictions are within 1 deg C of UKMO measured value

Preliminary results are encouraging, however, willneed to perform many more evaluations to be statistically significant!



• 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

Summary

Documents

An Android Based Mobile Heat Stress App