pkextractogr(1)

NAME
pkextractogr - extract pixel values from raster image from a (vector or raster) sample

SYNOPSIS
pkextractogr
-i input [-s sample | -rand number | -grid size] -o output [options]

DESCRIPTION
pkextractogr extracts pixel values from an input raster dataset, based on the locations you provide via a sample file. Alternatively, a random sample or systematic grid of points can also be extracted. The sample can be a vector file with points or polygons. In the case of polygons, you can either extract the values for all raster pixels that are covered by the polygons, or extract a single value for each polygon such as the centroid, mean, median, etc. As output, a new copy of the vector file is created with an extra attribute for the extracted pixel value. For each raster band in the input image, a separate attribute is created. For instance, if the raster dataset contains three bands, three attributes are created (b0, b1 and b2).

A typical usage of pkextractogr is to prepare a training sample for one of the classifiers implemented in pktools.

Overview of the possible extraction rules:
Extraction rule | Output features
point | Extract all pixel values covered by the polygon (option \FC-polygon\F[] not set) or extract a pixel on the surface option (\FC-polygon\F[] set).
allpoints | Extract all pixel values covered by the polygon.
centroid | Extract pixel value at the centroid of the polygon.
mean | Extract average of all pixel values within the polygon.
stdev | Extract standard deviation of all pixel values within the polygon.
median | Extract median of all pixel values within the polygon.
min | Extract minimum value of all pixels within the polygon.
max | Extract maximum value of all pixels within the polygon.
sum | Extract sum of the values of all pixels within the polygon.
mode | Extract the mode of classes within the polygon (classes must be set with the option class).
proportion | Extract proportion of class(es) within the polygon (classes must be set with the option class).
count | Extract count of class(es) within the polygon (classes must be set with the option class).
percentile | Extract percentile as defined by option perc (e.g, 95th percentile of values covered by polygon).

OPTIONS

\FC-i\F[] filename, \FC--input\F[] filename
    Raster input dataset containing band information

\FC-s\F[] sample, \FC--sample\F[] sample
    OGR vector dataset with features to be extracted from input data. Output will contain features with input band information included. Sample image can also be GDAL raster dataset.

\FC-ln\F[] layer, \FC--ln\F[] layer
    Layer name(s) in sample (leave empty to select all)

\FC-rand\F[] number, \FC--random\F[] number
    Create simple random sample of points. Provide number of points to generate

\FC-grid\F[] size, \FC--grid\F[] size
    Create systematic grid of points. Provide cell grid size (in projected units, e.g,. m)

\FC-o\F[] filename, \FC--output\F[] filename
    Output sample dataset Output sample dataset

\FC-c\F[] class, \FC--class\F[] class
    Class(es) to extract from input sample image. Leave empty to extract all valid data pixels from sample dataset. Make sure to set classes if rule is set to mode, proportion or count.

\FC-t\F[] threshold, \FC--threshold\F[] threshold
    Probability threshold for selecting samples (randomly). Provide probability in percentage (>0) or absolute (<0). Use a single threshold per vector sample layer. If using raster land cover maps as a sample dataset, you can provide a threshold value for each class (e.g. \FC-t\F[] 80 \FC-t\F[] 60). Use value 100 to select all pixels for selected class(es)

\FC-perc\F[] percentile, \FC--perc\F[] percentile
    Percentile value used for rule percentile

\FC-f\F[] format, \FC--f\F[] format
    Output sample dataset format

\FC-ft\F[] fieldType, \FC--ftype\F[] fieldType
    Field type (only Real or Integer)

\FC-lt\F[] labelType, \FC--ltype\F[] labelType
    Label type: In16 or String

\FC-b\F[] band, \FC--band\F[] band
    Band index(es) to extract. Leave empty to use all bands

\FC-sband\F[] band, \FC--startband\F[] band
    Start band sequence number

\FC-eband\F[] band, \FC--endband\F[] band
    End band sequence number

\FC-r\F[] rule, \FC--rule\F[] rule
    Rule how to report image information per feature (only for vector sample). point (value at each point or at centroid if polygon), centroid, mean, stdev, median, proportion, count, min, max, mode, sum, percentile.

\FC-bndnodata\F[] band, \FC--bndnodata\F[] band
    Band(s) in input image to check if pixel is valid (used for srcnodata)

\FC-srcnodata\F[] value, \FC--srcnodata\F[] value
    Invalid value(s) for input image

\FC-tp\F[] threshold, \FC--thresholdPolygon\F[] threshold
    (absolute) threshold for selecting samples in each polygon

\FC-buf\F[] value, \FC--buffer\F[] value
    Buffer for calculating statistics for point features

\FC-circ\F[], \FC--circular\F[]
    Use a circular disc kernel buffer (for vector point sample datasets only, use in combination with buffer option)

\FC-v\F[] level, \FC--verbose\F[] level
    Verbose mode if > 0