polytopoints: polygons to points

In ndvits: NDVI Time series extraction and analysis

Description

From a shape/kml file with polygons, the function creates a new shapefile with the grid of all the points inside the polygons.
It takes into account the spatial resolution of the images. A point is created if the center of the pixel is inside the polygon. Therefore, the new shapefile has no more than one point per pixel. The shapefile is projected with the same projection than the map.

Usage

polytopoints(shapefile, shapedir, ndvidirectory, region, Ystart, shapeext = "shp", type = "VITO_CLIP", outname = "buffer", outdir = ".")

Arguments

shapefile	name of the shape/kml file with polygons to be transformed in points. For a shapefile called ‘name.shp’ , shapefile="name". For a kml file, write the name of the layer.
shapedir	path to the shape/kml file. For a shapefile, shapedir is the path to the folder containing the shapefile. For example if the directory of the shapefile is ‘C:/Dir/name.shp’, shapefile="C:/Dir/". For a kml file, shapedir is the full directory of the kml file. For example shapefile="C:/Dir/name.kml". Please note that paths to files in R can be specified with either "/" or "\\" in Windows OS and "/" in UNIX OS.
ndvidirectory	path to the ndvi images folder (GeoTIFF files). /cr Please note that paths to files in R can be specified with either "/" or "\\" in Windows OS and with "/" in UNIX OS.
region	name of the region, same as in the name of the ndvi images.
Ystart	starting year of the analysis (in four-digit format).
shapeext	extension of the shape/kml file : "shp" for a Esri shapefile or "kml" for a kml file from Google earth . By default, shapeext = "shp".
type	type of nomenclature followed by the NDVI images : "VITO_CLIP", "VITO_VGT" or "GIMMS" (see details for more information). By default, type = "VITO_CLIP".
outname	name of the new shapefile. By default, outname = "buffer".
outdir	directory where the new shapefile will be saved. By default, outdir = "."(the current directory).

Details

More about the variable type :
type = GIMMS : nomenclature from Global Land Cover Facility
[RE][YY][MMM][DDD].[SAT]-VIg.tif

• RE : identifies the continent (AF for Africa,AZ for Australia and New Zealand, EA for Eurasia, NA for North America and SA for South America and Central America)

• YY : the two last digits of the year

• MMM : three-letter abbreviation of the month

• DDD : identifies the composite period, 15a denotes the days 1-15 of the month, and 15b denotes the days from 16 to the end of the month.

• SAT : identifies the satellite, NOAA-7, 9, 11, 14, 16, or 17 from which the data originated.
  

type = VITO_VGT : FreeVGT VITO's nomenclature
NDV_[YYYYMMDD]_[REGION]_Extract.tif

• YYYY : identifies the year (four digits)

• MM : identifies the months (two digits)

• DD : identifies the date of the period : "01", "11" or "21" (10-day composite).

• REGION : idendifies the region selected while extracting maps
  

type = VITO_CLIP : nomenclature after clipping the images in a particular region.
[REGION][YYYY]M[MM]P[D].tif

• REGION : the region as entered while clipping data.

• YYYY : identifies the year (four digits)

• MM : identifies the months (two digits)

• D : identifies the period (0, 1 or 2).

Value

Nothing is returned but a shapefile is created and saved in the folder outdir under the name outname.

Author(s)

Romain Frelat and Bruno Gerard

See Also

pointtobuffer

Examples

#There is no shapefile with polygons for the moment

ndvits documentation built on May 2, 2019, 4:47 p.m.