Difference between revisions of "Import of kNN"
Jump to navigation
Jump to search
| (One intermediate revision by one other user not shown) | |||
| Line 1: | Line 1: | ||
| + | [[Category:User's Guides|PlanStart|PlanStart]] | ||
| + | [[Category:PlanStart]] | ||
| + | [[Category:Database]] | ||
| + | |||
'''The ''k''NN-Sweden data''' consist of pixelwise estimates of forest states. A complete coverage is possible by using remotely sensed information, usually satellite image data. Sensors onboard, e.g., a SPOT satellite obtain spectral signatures in different wavelength bands (usually IR, R, G, and B) in each pixel, with a ground resolution approx. corresponding to 25 by 25 meters. Geo-referenced, previously inventoried NFI-plots will serve as reference data. In a feature space, defined by the satellite image, the ''k'' Nearest Neighbours (usually with ''k'' = 10) are found among the reference plots. Estimations of volume, age, tree species composition, etc. are then derived as weighted mean values (e.g. weighted inversely proportional to the distance in the feature space). | '''The ''k''NN-Sweden data''' consist of pixelwise estimates of forest states. A complete coverage is possible by using remotely sensed information, usually satellite image data. Sensors onboard, e.g., a SPOT satellite obtain spectral signatures in different wavelength bands (usually IR, R, G, and B) in each pixel, with a ground resolution approx. corresponding to 25 by 25 meters. Geo-referenced, previously inventoried NFI-plots will serve as reference data. In a feature space, defined by the satellite image, the ''k'' Nearest Neighbours (usually with ''k'' = 10) are found among the reference plots. Estimations of volume, age, tree species composition, etc. are then derived as weighted mean values (e.g. weighted inversely proportional to the distance in the feature space). | ||
| − | By ''k''NN imputation the forest state of a stand is described by sample plots, seemingly field inventoried in the current stand. Some things give the hoax away though; the within-stand variation regarding volume, age, etc. might be either | + | By ''k''NN imputation the forest state of a stand is described by sample plots, seemingly field inventoried in the current stand. Some things give the hoax away though; the within-stand variation regarding volume, age, etc. might be either unrealistically low (if the imputation is done "with replacement", i.e. one reference plot can represent a stand more than once) or unrealistically high (e.g., Maturity class K1 and S1 should not occur in the same stand, such stand should in real life be split into two stands). |