DATA SOURCES - DATA SOURCES Primary data collection some of...

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DATA SOURCES Primary data collection some of the data in a spatial database may have been measured directly o e.g. by field sampling or remote sensing the density of sampling determines the resolution of the data o e.g. samples taken every hour will capture hour-to- hour variation, but miss shorter-term variation o e.g. samples taken every 1 km will miss any variation at resolutions less than 1 km a sample is designed to capture the variation present in a larger universe o e.g. a sample of places should capture the variation present at all possible places o e.g. a sample of times will be designed to capture variation at all possible times there are several standard approaches to sampling: o in a random sample, every place or time is equally likely to be chosen o systematic samples are chosen according to a rule, e.g. every 1 km, but the rule is expected to create no bias in the results of analysis, i.e. the results would have been similar if a truly random sample had been taken
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DATA SOURCES - DATA SOURCES Primary data collection some of...

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