Approved For Public Release; Distribution Unlimited
US Army Research, Development & Engineering Command
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
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david.sauter@us.army.mil
575-678-2078 [DSN 258-]
Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
An Android Based Mobile Heat Stress App
Outline
• Background
• Hot Environment Assessment Tool
(HEAT) Overview
• Inputs/Output
• Validation Status
• Summary
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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
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Issues:
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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.
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Background (2 of 2)
Solution:
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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.
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Approved For Public Release; Distribution Unlimited
Approved For Public Release; Distribution Unlimited
Hot Environment Assessment Tool
(HEAT) Overview
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Available on Personal Digital Assistant (PDA), Apple iPhone/iPod Touch and
Android 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.
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Approved For Public Release; Distribution Unlimited
Inputs (1 of 3)
SITE tab:
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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)
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Inputs (2 of 3)
MET (“Meteorological”) tab:
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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:
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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
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Approved For Public Release; Distribution Unlimited
Output (2 of 2)
INFO tab:
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Information on app version and
developer point of contact
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Approved For Public Release; Distribution Unlimited
Validation Status
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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, will
need to perform many more evaluations to be
statistically significant!
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Approved For Public Release; Distribution Unlimited
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
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