# Product Information

Before you start downloading data, you first need to know which data you need and for which purpose. And not unimportant: you need to know where to find it. Although data discovery is not the primary objective of this package, it provides several instruments to obtain product information.

## The Web Browser

Perhaps the easiest way to find products and layers is via the online catalogue. To streamline your workflow using the web browser, you should check `vignette("translate")`. That vignette explains how you can copy a request from the web browser catalogue and use it in R.

## Listing Products

To get a complete overview of all available products, you can list them with either `cms_products_list()` or `cms_products_list2()`:

    library(CopernicusMarine)

    cms_products_list() |> head(3)
    #> # A tibble: 3 × 19
    #>   product_id         catalogue title thumbnailUrl sources processingLevel areas
    #>   <chr>              <chr>     <chr> <chr>        <list>  <chr>           <list>
    #> 1 GLOBAL_ANALYSISFO… CMEMS     Glob… https://mdl… <list>  Level 4         <list>
    #> 2 GLOBAL_ANALYSISFO… CMEMS     Glob… https://mdl… <list>  Level 4         <list>
    #> 3 GLOBAL_ANALYSISFO… CMEMS     Glob… https://mdl… <list>  Level 4         <list>
    #> # ℹ 12 more variables: geoResolution <list>, vertLevels <int>,
    #> #   tempExtentBegin <chr>, tempResolutions <list>, stacOrCswBbox <list>,
    #> #   stacOrCswTbox <list>, mainVariables <list>, `_isViewableOmi` <lgl>,
    #> #   numLayers <int>, thumbnailMeta <list>, tempExtentEnd <chr>,
    #> #   omiFigureUrl <chr>

    cms_products_list2() |> head(3)
    #> $`C3S-GLO-SST-L4-REP-OBS-SST`
    #> [1] "SST_GLO_SST_L4_REP_OBSERVATIONS_010_024"
    #>
    #> $`CERSAT-GLO-SEAICE_30DAYS_DRIFT_ASCAT_SSMI_MERGED_RAN-OBS_FULL_TIME_SERIE`
    #> [1] "SEAICE_ARC_SEAICE_L3_REP_OBSERVATIONS_011_010"
    #>
    #> $`CERSAT-GLO-SEAICE_30DAYS_DRIFT_QUICKSCAT_SSMI_MERGED_RAN-OBS_FULL_TIME_SERIE`
    #> [1] "SEAICE_ARC_SEAICE_L3_REP_OBSERVATIONS_011_010"

The first returns a `data.frame` complete with al sorts of meta information about the type of variables in the product, the spatio-temporal coverage, number of vertical layers, etc. You can use this `data.frame` to narrow your search by applying a `dplyr::filter()` on it.

You can even pass arguments that are used to search the online catalogue. These are not well documented. The example below shows how to search for free text and filter on area and variables:

    cms_products_list(freeText = "wave",
                      facetValues = list(areas             = list("Europe"),
                                         specificVariables = list("Velocity")))
    #> # A tibble: 1 × 16
    #>   product_id         catalogue title thumbnailUrl sources processingLevel areas
    #>   <chr>              <chr>     <chr> <chr>        <chr>   <chr>           <list>
    #> 1 SEALEVEL_EUR_PHY_… CMEMS     EURO… https://mdl… Satell… Level 3         <list>
    #> # ℹ 9 more variables: geoResolution <list>, tempExtentBegin <chr>,
    #> #   tempResolutions <chr>, stacOrCswBbox <list>, stacOrCswTbox <list>,
    #> #   mainVariables <chr>, `_isViewableOmi` <lgl>, numLayers <int>,
    #> #   thumbnailMeta <list>

The reason this is poorly documented is because this function does not use the formal API. Instead it uses the web-form used by the online catalogue. Users should therefore not rely on it too much as it may get discontinued or altered at any time.

Instead, users can use `cms_products_list2()` which produces a list of products, by using the official API. Unfortunately, this list does not contain any additional information. For this purpose users can refer to `cms_product_metadata()`, `cms_product_details()`, or `cms_product_services()` as described below.

## Product Details

With `cms_product_details()` you will get some descriptive information about your product. Nothing too fancy, but it will help you understand what the product is all about.

    cms_product_details("GLOBAL_ANALYSISFORECAST_PHY_001_024") |> summary()
    #>                 Length Class  Mode
    #> id               1     -none- character
    #> type             1     -none- character
    #> stac_version     1     -none- character
    #> stac_extensions  1     -none- list
    #> title            1     -none- character
    #> description      1     -none- character
    #> license          1     -none- character
    #> providers        2     -none- list
    #> keywords        39     -none- list
    #> links           30     -none- list
    #> extent           2     -none- list
    #> assets           1     -none- list
    #> properties      32     -none- list
    #> sci:doi          1     -none- character

## Product Metadata

When subsetting a dataset with `cms_download_subset()`, the most tricky thing is discovering what the available ranges are for its dimensions. You can use `cms_product_metadata()` for this purpose. It returns a named list.

    meta_info <- cms_product_metadata("GLOBAL_ANALYSISFORECAST_PHY_001_024")

    ## Get the dimension properties for the first layer in this product
    meta_info$properties[[1]]$`cube:dimensions` |> summary()
    #>           Length Class  Mode
    #> latitude  5      -none- list
    #> longitude 5      -none- list
    #> elevation 5      -none- list
    ## Get the variable properties for the first layer in this product
    meta_info$properties[[1]]$`cube:variables` |> summary()
    #>     Length Class  Mode
    #> e1t 23     -none- list
    #> e2t 23     -none- list
    #> e3t 23     -none- list

Another way to get the dimension ranges is by setting up a stars proxy object (see `vignette("proxy")`) and call `st_dimensions()` on it:

    library(stars) |> suppressMessages()

    myproxy <- cms_zarr_proxy(
        product       = "GLOBAL_ANALYSISFORECAST_PHY_001_024",
        layer         = "cmems_mod_glo_phy-cur_anfc_0.083deg_P1D-m",
        asset         = "timeChunked")
    st_dimensions(myproxy)
    #>           from   to     offset  delta  refsys
    #> longitude    1 4320         NA     NA      NA
    #> latitude     1 2041         NA     NA      NA
    #> elevation    1   50         NA     NA udunits
    #> time         1 1416 2022-06-01 1 days    Date
    #>                                                            values x/y
    #> longitude            [-180.0417,-179.9583),...,[179.875,179.9584) [x]
    #> latitude            [-80.04167,-79.95833),...,[89.95834,90.04166) [y]
    #> elevation [-5727.917,-5274.784) [m],...,[-0.494025,0.5533251) [m]
    #> time                                                         NULL

## Product Services

If you want a more raw access point to your data, you can use `cms_product_services()`. It will present a `data.frame` for your product with all services provided by Copernicus. You can use any of the columns with the `"_href"` suffix to get an URL of a specific service. If you want to access those directly, you are on your own. It is easier to use any of the wrappers provided by this package to access the data.

    cms_product_services("GLOBAL_ANALYSISFORECAST_PHY_001_024")
    #> # A tibble: 22 × 61
    #>    id        type  stac_version stac_extensions geometry     bbox   properties
    #>    <chr>     <chr> <chr>        <chr>           <list>       <list> <list>
    #>  1 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  2 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  3 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  4 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  5 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  6 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  7 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  8 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #>  9 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #> 10 cmems_mo… Feat… 1.0.0        https://stac-e… <named list> <list> <named list>
    #> # ℹ 12 more rows
    #> # ℹ 54 more variables: links <list>, collection <chr>, native_id <chr>,
    #> #   native_href <chr>, native_type <chr>, native_roles <chr>,
    #> #   native_title <chr>, native_description <chr>, wmts_id <chr>,
    #> #   wmts_href <chr>, wmts_type <chr>, wmts_roles <chr>, wmts_title <chr>,
    #> #   wmts_description <chr>, static_id <list<list>>, static_href <list<list>>,
    #> #   static_type <list<list>>, static_roles <list<list>>, …