Predicting GPS Signal Loss in Forests Using Sky-Oriented Photography University of Florida

USMA Research Unit Affiliation

Center for Environmental and Geographical Science

Date of Award


Degree Type

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation




We depend on numerous technologies that use microwave signals. The reception of these signals is degraded by reflection, absorption, and scattering due to propagation through vegetation. Understanding how these signals are influenced by vegetation structure allows for the determination of how specific technologies may be affected in different forest environments. This study presents different models that predict signal loss in forested areas and discusses different factors that influence signal loss in forested areas. In this research we explore the relationships between forest parameters obtained using traditional mensuration techniques and terrestrial-based hemispherical sky-oriented photos, Global Positioning System (GPS) signal-to-noise ratios, and individual GPS signal dropouts. Hemispherical sky-oriented photos can be used to rapidly estimate leaf area index and canopy closure values at particular angles from zenith in forested areas using ArcGIS software. The relationships between changes in the observed signal-to-noise ratios of received GPS L-band signals under forest canopies and forest parameter estimates calculated using hemispherical sky oriented photos and traditional forest measurements are used to model signal attenuation. Using ordinary least squares linear regression modeling, we present

15 predictive models for both a managed pine forest and a natural deciduous forest, as well as, explore the unique factors associated with different seasons in each environment. We also explore the influence on different models within different forest species and geographic locations as well as methods to employ a predictive model. The resulting models predict signal attenuation while using only the minimum number of statistically significant parameters taken from sky-oriented photos and GPS receivers allowing for simple and rapid replication.

Modernization Priorities Supported

Army Network, Soldier Lethality

USMA Research Goals Supported

Develop the Faculty Professionally, Address Important Issues Facing the Army and Nation, Enhance the Reputation of USMA

Partnered Organization(s)


First Advisor

Benjamin E. Wilkinson

Second Advisor

Wendell Cropper Jr

Third Advisor

Bon Dewitt


University of Florida

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