Post on 25-Feb-2016
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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
david.sauter@us.army.mil575-678-2078 [DSN 258-]
WIDA Conference - Mar 2012
US Army Research, Development & Engineering Command
2 Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
• Background• Hot Environment Assessment Tool
(HEAT) Overview• Inputs/Output • Validation Status• Summary
Outline
An Android Based Mobile Heat Stress App
3 Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
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
4 Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
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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5 Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
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.
6 Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
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 Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
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
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Approved For Public Release; Distribution Unlimited
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
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Approved For Public Release; Distribution Unlimited
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 Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
Output (2 of 2)
INFO tab: • Information on app version and
developer point of contact
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Approved For Public Release; Distribution Unlimited
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!
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Approved For Public Release; Distribution Unlimited
• 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