Two forms of source data 1.“ Point' data usually an irregular(scattered)network of survey sites at which observations/measurements are made soil, vegetation, topography, wildlife, climate Problem How to spatially extend data from point to area? 2. Spatially distributed data values recorded on a regular grid satellite imagery eg, LANDSAT, AVHRR Problem What do spectral values mean?Two forms of source data: 1. ‘Point’ data - usually an irregular (scattered) network of survey sites at which observations/measurements are made - soil, vegetation, topography, wildlife, climate Problem: How to spatially extend data from point to area? 2. Spatially distributed data - values recorded on a regular grid - satellite imagery eg, LANDSAT , AVHRR Problem: What do spectral values mean?