stac_dem_bc

The goal of stac_dem_bc is to serve the British Columbia lidarBC digital elevation model collection. It can be queried by location and/or time using our API via the lovely rstac R package and QGIS (v3.42+). Still a work in progress but currently functioning at https://images.a11s.one. See below how to add STAC items to QGIS.

This work leverages work in a sister repo stac_uav_bc with the registration of the stac done with scripts here and here.

Here we will use bcdata (indirectly through our Reproducable Field Projects rfp package) to give us the Bulkley River watershed group - then query the stac-dem-bc collection for all the DEMs that land in that watershed group for the timeframe between 2018 and 2020.

aoi <- rfp::rfp_bcd_get_data(
  "whse_basemapping.fwa_watershed_groups_poly",
  col_filter = "watershed_group_name",
  col_filter_value = "Bulkley River"
) |> 
  sf::st_transform(crs = 4326)

# we don't use this but could feed to the `bbox` param
bbox <- aoi |> 
  sf::st_bbox() |> 
  as.numeric()

date_start <- "2018-01-01T00:00:00Z"
date_end <- "2020-12-31T00:00:00Z"

# use rstac to query the collection
q <- rstac::stac("https://images.a11s.one/") |>
  rstac::stac_search(
    # collections = "imagery-uav-bc-dev",
    collections = "stac-dem-bc",
    # bbox = bbox,
    intersects = jsonlite::fromJSON(
      geojsonsf::sf_geojson(
        aoi, atomise = TRUE, simplify = FALSE
      ),
      simplifyVector = FALSE
      # ugly but just grabs the geometry list item using the new pipe
    ) |> (\(x) x$geometry)(),
    datetime = paste0(date_start, "/", date_end)
  ) |>
  rstac::post_request()

# get deets of the items
r <- q |>
  rstac::items_fetch()

# burn the results locally so we can serve it instantly on index.html builds
# Save to RDS file
saveRDS(r, "data/stac_result.rds")

r <- readRDS("data/stac_result.rds")
# build the table to display the info
tab <- tibble::tibble(url_download = purrr::map_chr(r$features, ~ purrr::pluck(.x, "assets", "image", "href"))) |> 
  dplyr::mutate(
    link_download = ngr::ngr_str_link_url(url_base = url_download, anchor_text = url_download)
  ) |> 
  dplyr::select(link_download)

DEM download links. NOTE: To view all columns in the table - please click on one of the sort arrows within column headers before scrolling to the right.

As of QGIS 3.42 - ONE can also access stac items (orthoimagery, Digital Surface Models and Digital Terrain Models in our case) directly via the Data Source Manager. See a blog with details here. It looks like this in the th Layer / Data Source Manager toolbar in QGIS:

Connecting to https://images.a11s.one

Using the field of view in QGIS to filter results