Paper Info
Title
Normalized Microwave Reflection Index: Validation of Vegetation Water Content Estimates From Montana Grasslands
Abstract
The Normalized Microwave Reflection Index (NMRI) measures the intensity of GPS reflections, which is affected by vegetation within ~100 m of GPS antennas. In a companion paper, the theoretical basis for NMRI and how it is derived from data archived at geodetic GPS installations are described. NMRI is calculated by normalizing the standard GPS metric MP1rms on a site-by-site basis to minimize terrain effects. Here, we validate NMRI as a metric for estimating vegetation water content (VWC) and evaluate the normalization procedure. In situ measurements of plant height, biomass, and VWC were taken on a biweekly basis during 2012 at four grassland sites in Montana. These measurements were compared to time series of MP1rms, NMRI, and Normalized Difference Vegetation Index (NDVI) from each site. At each site, a significant linear relationship exists between MP1rms and VWC. However, this relationship is not consistent across sites. Once normalized, a linear relationship exists between NMRI and VWC (r2=0.71) that is consistent across the four sites. This suggests that VWC could be predicted from NMRI at sites without in situ observations, as long as vegetation and climate are similar. There is no clear relationship between NMRI and either vegetation height or biomass. The importance of normalization is shown using data from eight additional sites. After normalization, a strong positive correlation is apparent between NMRI and NDVI across all grassland GPS sites in Montana.
Year
DOI
Venue
2014
10.1109/JSTARS.2014.2320597
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of  
Keywords
Field
DocType
global positioning system,antennas,geodesy,time series,vegetation,vegetation mapping,ad 2012,gps antennas,gps reflections,montana grassland sites,normalized difference vegetation index,normalized microwave reflection index,biomass,geodetic gps installations,grassland gps sites,normalization procedure,plant height,standard gps metric mp1rms,terrain effects,vegetation height,vegetation water content estimates,remote sensing,indexes
Vegetation,Normalization (statistics),Remote sensing,Vegetation water content,Microwave reflection,Normalized Difference Vegetation Index,Positive correlation,Enhanced vegetation index,Mathematics
Journal
Volume
Issue
ISSN
7
5
1939-1404
Citations 
PageRank 
References 
2
0.40
3
Authors
3
Name
Order
Citations
PageRank
Eric E. Small112918.61
Kristine M. Larson29715.30
Smith, W.K.320.40