gvmi: Global Vegetation Moisture Index

In ASIP: Automated Satellite Image Processing

Description

Global Vegetation Moisture Index (GVMI) is suitable for retrieving vegetation water content when the LAI is equal to or greater than 2. For sparsely vegetated area, where LAI is less than 2, further research is required to understand the role of soil effects on reflectance measured in the all-optical spectrum (Ceccato et, al. 2002).

Usage

gvmi(directory = getwd(), crop = "n", ext2crop = "none")

Arguments

ext2crop, crop, directory

Same as mentioned in arvi.

Value

Computed GVMI product

Note

1. GVMI = ((r_nir + 0.1)- (r_swir2+0.2))/ ((r_nir + 0.1)- (r_swir2+0.2))

where, "r_" denotes TOA reflectance band. Other important notes are mentioned in custom.eqn.

References

Ceccato P, Gobron N, Flasse S, Pinty B and Tarantola S (2002) Designing a spectral index to estimate vegetation water content from remote sensing data: Part 1: Theoretical approach. Remote Sensing of Environment, 82(2-3), pp:188-197. doi:10.1016/S0034-4257(02)00037-8.

Examples

library (raster)
library (rgdal)
# Finding the path of the sample satellite image directory.
# User may define paths directly like "/home/ur_folder" or "C:/ur_folder"
path <- system.file ("TM_sample", package = "ASIP")
shapefil <- paste0 (path, "/test.shp")
op <- gvmi (directory = path, crop = "y", ext2crop = shapefil)

Example output

Loading required package: sp
rgdal: version: 1.5-18, (SVN revision 1082)
Geospatial Data Abstraction Library extensions to R successfully loaded
Loaded GDAL runtime: GDAL 3.0.4, released 2020/01/28
Path to GDAL shared files: /usr/share/gdal
GDAL binary built with GEOS: TRUE 
Loaded PROJ runtime: Rel. 6.3.1, February 10th, 2020, [PJ_VERSION: 631]
Path to PROJ shared files: /usr/share/proj
Linking to sp version:1.4-4
To mute warnings of possible GDAL/OSR exportToProj4() degradation,
use options("rgdal_show_exportToProj4_warnings"="none") before loading rgdal.
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ASIP documentation built on May 1, 2019, 10:17 p.m.