Leaf Area Index (LAI) is defined as the one sided green leaf area per unit ground area in broadleaf canopies, or as the projected needle leaf area per unit ground area in needle canopies. The interaction between vegetation surface and the atmosphere, e.g. radiation uptake, precipitation interception, energy conversion, momentum and gas exchange, is substantially determined by the vegetation surface (Monteith and Unsworth, 1990). Various destructive and non-destructive methodologies to measure or derive LAI do exist. Non-destructive methods include hemispherical photography, sun fleck ceptometers, and other optical instruments like TRAC, LAI-2000 or LI-COR (detailed description of techniques are presented by Chen et al., 1997). In this study the non-destructive method was used. A plant canopy analyser was used in this regard. It has to be taken into account that all methods do have advantages as well as disadvantages in estimating LAI and data are not always directly comparable. Leaf area index (LAI) is one of the major parameter for determining the crop growth that may be derived from optical remote sensing. LAI during the plucking stage is one of the most important factors. LAI helps in determining the crop reflectance. Relationship between LAI and NDVI is an important factor for predicting the yield. It can be considered as a measure of plant productivity (Sellers, 1985). The Normalized Difference Vegetation Index (NDVI) can be considered as a measure of LAI for most of the crops (Gong et. al., 1995). So this relationship can be used for determining the productivity of the tea plantation. Estate latitude, longitude, the acreage, the varieties grown, slope, elevation of the estate, the average annual rainfall of the area, temperature, daily sunshine hour and the relative humidity are the parameters important to carry out the study. The Daily temperature should range from 21 to 230 C. Both attribute and spatial data along with estate record, meteorological data and the measured LAI were used for the analysis. Spatial data may be verified from field samples collected for measuring the LAI. Sample size may vary depending on the requirement. Leaf area was determined by using plant canopy analyzer. The plant canopy analyzer gives the LAI values directly using the equation given below:  ..............(1)The tea plant canopy coverage has to be considered from the satellite imagery. Both leaf area and the sample area should have the units.  ...............(2)where,  .............(3)The Leaf Area Index (LAI) values were collected using the Plant Canopy Analyzer from the tea fields and the GPS point at that particular point was recorded. Three LAI observations were taken from each division of the gardens. The average LAI values for each division were calculated. These LAI values and the GPS points of the gardens were then overlaid over the different images. Using the MODIS LAI values and the field LAI values the LAI variability has been studied. Details of this have been discussed in the results and discussion chapter.  Figure 11: LANDSAT Image Showing the LAI of a Healthy Patch |