Get a data product
Arguments
- layer
(character) Identifier of the data product. See mrp_list
- path
(character) Path to save the requests. Default is
base::tempdir(). See details.- cql_filter
(character) Contextual Query Language (CQL) filter. See details.
- filter
(character) Standard OGC filter specification. See details.
- count
(numeric) Maximum number of features to be retrieved.
Details
This function uses WFS services to download the Marine Regions layers as ESRI Shapefiles.
Caching
By default, the layers are downloaded to a temporal directory (base::tempdir()). You can provide
a path in the path argument. But you can also set a path with # options("mregions2.download_path" = "my/path/").
Because it is possible to add filters, each request is identified with a crc32 hash, provided with
digest::digest() and attached to the file downloaded.
Once a layer is downloaded, it will be read from the cache during the next two weeks. To avoid this, simply delete the layers in the cache path.
Filters
Both the Contextual Query Language (CQL) filter and the standard OGC filter specification allow to query the server before performing a request. This will boost performance as you will only retrieve the area of your interest. It is possible to query on attributes, but also perform geospatial queries. For instance, you can query a bounding box of interest.
CQL filters are possible only in geoserver. Marine Regions uses a geoserver instance to serve its data products. A tutorial on CQL filters is available in the geoserver web site.
See also
mrp_list to describe the list of products, mrp_view() to visualize the data product in advance, mrp_colnames() and mrp_col_unique() to get the name, data type and unique values of a the columns of a data product, useful to query
with the arguments cql_filter or filter
Examples
# \donttest{
# Set cache path. Default is a temporal directory
options(mregions2.download_path = tempdir())
getOption("mregions2.download_path")
#> [1] "/tmp/RtmpFLYzaa"
#> [1] "/tmp/RtmpARLgoE"
# See the list of all data products
mrp_list
#> # A tibble: 21 × 8
#> title namespace layer license citation doi imis abstract
#> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr>
#> 1 Exclusive Economic Zon… MarineRe… eez Creati… "Flande… http… http… "Versio…
#> 2 Maritime Boundaries (v… MarineRe… eez_… Creati… "Flande… http… http… "Versio…
#> 3 Territorial Seas (12 N… MarineRe… eez_… Creati… "Flande… http… http… "Versio…
#> 4 Contiguous Zones (24 N… MarineRe… eez_… Creati… "Flande… http… http… "Versio…
#> 5 Internal Waters (v3, w… MarineRe… eez_… Creati… "Flande… http… http… "Versio…
#> 6 Archipelagic Waters (v… MarineRe… eez_… Creati… "Flande… http… http… "Versio…
#> 7 High Seas (v1, world, … MarineRe… high… Creati… "Flande… http… http… "High S…
#> 8 Extended Continental S… MarineRe… ecs Creati… "Flande… http… http… "This d…
#> 9 Extended Continental S… MarineRe… ecs_… Creati… "Flande… http… http… "This d…
#> 10 IHO Sea Areas (v3) MarineRe… iho Creati… "Flande… http… http… "World …
#> # ℹ 11 more rows
# We want the Exclusive Economic Zones of Portugal. Let's first visualize the product:
mrp_view("eez")
# See all the columns on this data product
mrp_colnames("eez")
#> # A tibble: 31 × 3
#> layer colname type
#> * <chr> <chr> <chr>
#> 1 eez mrgid int
#> 2 eez geoname string
#> 3 eez mrgid_ter1 int
#> 4 eez pol_type string
#> 5 eez mrgid_sov1 int
#> 6 eez territory1 string
#> 7 eez iso_ter1 string
#> 8 eez sovereign1 string
#> 9 eez mrgid_ter2 int
#> 10 eez mrgid_sov2 int
#> # ℹ 21 more rows
# We should query on sovereign
# See all the possible values of sovereign1, sovereign2 and sovereign3
sov1 = mrp_col_unique("eez", "sovereign1")
sov2 = mrp_col_unique("eez", "sovereign2")
sov3 = mrp_col_unique("eez", "sovereign3")
# Is Portugal a value in the sovereign1, 2 and 3?
"Portugal" %in% sov1
#> [1] TRUE
#> [1] TRUE
"Portugal" %in% sov2
#> [1] FALSE
#> [1] FALSE
"Portugal" %in% sov3
#> [1] FALSE
#> [1] FALSE
# Portugal is only in sovereign1. Let's write a CQL filter to get only
# the EEZs of Portugal, or those where Portugal is a party of a dispute or a joint regime
portugal_eez <- mrp_get("eez", cql_filter = "sovereign1 = 'Portugal'")
# If you perform this request again, it will be read from the cache instead
portugal_eez <- mrp_get("eez", cql_filter = "sovereign1 = 'Portugal'")
#> Cache is fresh. Reading: /tmp/RtmpARLgoE/eez-1951c8b7/eez.shp
#> (Last Modified: 2023-04-24 17:45:16)
# You can also limit the number of features to be requested
mrp_get("eez", count = 5)
#> Simple feature collection with 5 features and 31 fields
#> Geometry type: MULTIPOLYGON
#> Dimension: XY
#> Bounding box: xmin: -173.7747 ymin: -56.22782 xmax: -10.93248 ymax: -4.537529
#> Geodetic CRS: WGS 84
#> # A tibble: 5 × 32
#> mrgid geoname mrgid_ter1 pol_type mrgid_sov1 territory1 iso_ter1 sovereign1
#> <int> <chr> <int> <chr> <int> <chr> <chr> <chr>
#> 1 8444 United St… 8670 200NM 2204 American … ASM United St…
#> 2 8379 British E… 8620 200NM 2208 Ascension SHN United Ki…
#> 3 8446 New Zeala… 8672 200NM 2227 Cook Isla… COK New Zeala…
#> 4 8389 Overlappi… 8623 Overlap… 2208 Falkland … FLK United Ki…
#> 5 8440 French Ex… 8656 200NM 17 French Po… PYF France
#> # ℹ 24 more variables: mrgid_ter2 <int>, mrgid_sov2 <int>, territory2 <chr>,
#> # iso_ter2 <chr>, sovereign2 <chr>, mrgid_ter3 <int>, mrgid_sov3 <int>,
#> # territory3 <chr>, iso_ter3 <chr>, sovereign3 <chr>, x_1 <dbl>, y_1 <dbl>,
#> # mrgid_eez <int>, area_km2 <int>, iso_sov1 <chr>, iso_sov2 <chr>,
#> # iso_sov3 <chr>, un_sov1 <dbl>, un_sov2 <dbl>, un_sov3 <dbl>, un_ter1 <dbl>,
#> # un_ter2 <dbl>, un_ter3 <dbl>, geometry <MULTIPOLYGON [°]>
# }