GEOG 7 Lecture Notes - Lecture 7: Spatial Database, Database, Digitizing
Document Summary
Gis data sources: check for existing data before creating | free data from government or for a fee (commercial) Primary data direct data capture: ground surveying, gps, mobile devices, tablets, phones. Secondary data recycling data from someone else: existing data from existing digital sources, digitizing existing sources, scanning maps: heads up digitizing, automated digitizing; semi-automatic approach is a good compromise, tolerances available. Data collection takes 85% of time, money and energy. Transformation among projections: organization of data storage. Adjustment at map edges between neighbor maps: correction of errors. Orthophotos: photo map with details corrected with map geometry. Error: difference between a true value and the observed, estimated or predicted value: based on sampling a population. Margin of error: degree of confidence for each data set. Measurement error: accuracy and precision: how close to actual value versus variance of a value when repeated measurements are taken, uncertainty in analysis: compounded effects of u1 and u2.
