spMetadata-methods: Methods to generate spatial metadata

Description

The spMetadata function will try to generate missing metadata (bounding box, location info, session info, metadata creator info and similar) for any Spatial* object (from the sp package) or Raster* object (from the raster package). The resulting object of class SpatialMetadata-class can be used e.g. to generate a Layer description documents ( tag). The read.metadata function can be used to read the formatted metadata (.xml), prepared following to the http://www.fgdc.gov/metadata/csdgm/{Federal Geographic Data Committee (FGDC) Content Standard for Digital Geospatial Metadata}, and convert them to a more readble format (data frame).

Usage

## S3 method for class 'RasterLayer':
spMetadata(obj, Target_variable, bounds, color, \dots )
## S3 method for class 'Spatial':
spMetadata(obj, xml.file, generate.missing = TRUE, Citation_title,
    Target_variable, Attribute_Measurement_Resolution = 1, 
    Attribute_Units_of_Measure = "NA",
    Indirect_Spatial_Reference = "", GoogleGeocode = FALSE, 
    Enduser_license_URL = get("license_url", envir = plotKML.opts),
    signif.digit = 3, colour_scale, bounds, legend_names, icons, 
    validate.schema = FALSE, Target_variable_descr = "NA", 
    Geosp_Data_Presentation_Form, Edition, Purpose, Abstract, 
    Supplinf, Publisher, Pub_Place, Temp_Ext,
    Update_Freq = c("Unknown", "Continually", "Daily", "Weekly", 
    "Monthly", "Annually", "As needed", "Irregular", "None planned"), 
    Stat_Progress = c("Complete", "In work", "Planned"), 
    Spatial_Represent_Type = c("Point", "Vector", "Raster"),
    Keyw_theme, Keyw_place )

Arguments

obj

some "Spatial" or "Raster" class object with "data" slot

xml.file

character; optional XML metadata file

generate.missing

logical; specifies whether to automatically generate missing fields

Citation_title

character; title of the bibliographic reference for this data set

Target_variable

character; target variable name

Attribute_Measurement_Resolution

numeric; detection limit i.e. measurement precision

Attribute_Units_of_Measure

character; measurement units

Indirect_Spatial_Reference

character; location name as on the topographic map

GoogleGeocode

logical; specifies whether the function should try to use GoogleGeocoding functionality to determine the location name

Enduser_license_URL

character; URL to the end user license

signif.digit

integer; the default number of significant digits (in the case of rounding)

colour_scale

the colour scheme used to visualize this data

bounds

numeric vector; upper and lower bounds used for visualization

color

character; colour legend (must match the bounds vector)

legend_names

character; legend names in the order of bounds

icons

character; file name or URL used for icons (if applicable)

validate.schema

logical; specifies whether to validate the schema using the xmlSchemaValidate

Target_variable_descr

character; specifies target variable description for eainfo-node 'attrdef'

Geosp_Data_Presentation_Form

character; defines node 'geoform'

Edition

defines the version of the title

Purpose

defines the purpose of the given layer

Abstract

defines the abstract of the given layer

Supplinf

defines the supplemental information of the given layer

Publisher

defines publishing organization (or individual)

Pub_Place

defines publication place ('pubplace')

Temp_Ext

defines temporal extent start/end

Update_Freq

defines update frequency

Stat_Progress

defines progress status

Spatial_Represent_Type

defines direct node (direct spatial reference method)

Keyw_theme

defines node(s) 'themekey'

Keyw_place

defines node(s) 'placekey'

...

additional arguments to be passed

Details

spMetadata tries to locate a metadata file in the working directory (it looks for a metadata file with the same name as the object name). If no .xml file exists, it will load the template xml file available in the system folder (system.file("FGDC.xml", package="plotKML")). The FGDC.xml file contains typical metadata entries with description and examples. For practical purposes, one metadata object in plotKML can be associated with only one variable i.e. one column in the "data" slot (specified via Target_variable). To prepare a metadata xml file for the layer of interest, consider using the http://plotkml.r-forge.r-project.org/FGDC.xml{FGDC.xml} template file; to enter the missing fields use e.g. the http://geology.usgs.gov/tools/metadata/tools/doc/tkme.html{Tkme} software: Another editor for formal metadata, by Peter N. Schweitzer (U.S. Geological Survey). Before commiting the metadata file, try also running a http://geo-nsdi.er.usgs.gov/validation/{validation test}. spMetadata tries to automatically generate the most usefull information, so that a user can easily find out about the input data and procedures followed to generate the visualization (KML). Typical metadata entries include e.g.:

metadata[["idinfo"]][["native"]]--- Session info e.g.: Produced using R version 2.12.2 (2011-02-25) running on Windows 7 x64.
metadata[["spdoinfo"]][["indspref"]]--- Indirect spatial reference estimated using thehttp://code.google.com/apis/maps/documentation/webservices/{Google Maps API Web Services}.
metadata[["idinfo"]][["spdom"]][["bounding"]]--- Bounding box in the WGS84 geographical coordinates estimated by reprojecting the original bounding box.

By default, plotKML uses the Creative Commons license, but this can be adjusted by setting the Enduser_license_URL argument above.

References

The Federal Geographic Data Committee, (2006) FGDC Don't Duck Metadata --- A short reference guide for writing quality metadata. Vers. 1,http://www.fgdc.gov/metadata/documents/MetadataQuickGuide.pdf
Content Standard for Digital Geospatial Metadata (http://www.fgdc.gov/metadata/csdgm/)
Template metadata file (http://plotkml.r-forge.r-project.org/FGDC.xml)
Tkme metadata editor (http://geology.usgs.gov/tools/metadata/tools/doc/tkme.html)
Creative Commons licenses (http://creativecommons.org/licenses/)

Examples

Run this code

## read metadata from the system file:
x <- read.metadata(system.file("FGDC.xml", package="plotKML"))
str(x)
## generate missing metadata
data(eberg)
coordinates(eberg) <- ~X+Y
proj4string(eberg) <- CRS("+init=epsg:31467")
## no metadata file specified:
eberg.md <- spMetadata(eberg, Target_variable="SNDMHT_A")
## with localy prepared metadata file:
eberg.md <- spMetadata(eberg, xml.file=system.file("eberg.xml", package="plotKML"), 
Target_variable="SNDMHT_A")
## print the results of validation (it needs to be able to connect to a URL with schema):
eberg.md <- spMetadata(eberg, Target_variable="SNDMHT_A", validate.schema = TRUE)
## write the metadata to a file:
saveXML(metadata(eberg.md), "eberg_SAND.xml")
## export to SLD format:
metadata2SLD(eberg.md, "eberg.sld")
## plot the layer with the metadata:
kml(eberg, file.name = "eberg_md.kml", colour = SNDMHT_A, metadata = eberg.md, kmz = TRUE)

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