Stratified Sampling of Satellite Images with a Systematic Grid of Points

Sampling satellite images presents some specific characteristics: images overlap and many of them fall partially outside the studied region. A careless sampling may introduce an important bias. This paper illustrates the risk of bias and the efficiency improvements of systematic, pps (probability proportional to size) and stratified sampling. A sampling method is proposed with the following criteria: a) Unbiased estimators are easy to compute, b) it can be combined with a stratification c) within each stratum, sampling probability is proportional to the area of the sampling unit, and d) the geographic distribution of the sample is reasonably homogeneous. Thiessen polygons computed on image centres are sampled through a systematic grid of points. The sampling rates in different strata are tuned by dividing the systematic grid into subgrids or replicates and taking for each stratum a certain number of replicates. The approach is illustrated with an application to the estimation of the geometric accuracy of Image2000, a Landsat ETM+ mosaic of the European Union.

GALLEGO PINILLA Francisco; 

2006-02-02

ELSEVIER GMBH

JRC32183

https://publications.jrc.ec.europa.eu/repository/handle/JRC32183,