For each pair of photos whose footprints intersect, computes the overlap area and the percentage of each photo's footprint that overlaps. Most useful on same-scale photos from the same flight.
Arguments
- photos_sf
An sf point object with a
scalecolumn. Geometry must be POINT — the ground footprint is estimated from a centroid, so passing footprints back in is refused rather than coerced.- dem
Optional elevation raster passed to
fly_footprint(), sizing each frame from its height above ground instead of the reported scale. See the Terrain section offly_footprint().
Value
A tibble with columns photo_a, photo_b, overlap_km2,
pct_of_a, and pct_of_b. Only pairs with non-zero overlap are returned.
Details
Overlap percentages are estimates from fly_footprint(), and inherit
whatever basis it was given. Without dem that is the reported scale, which
assumes flat ground and understates footprint area wherever the terrain sits
below the elevation the scale was computed for. Pass dem to size each frame
from its height above ground instead — see the Terrain section of
fly_footprint().
Examples
centroids <- sf::st_read(system.file("testdata/photo_centroids.gpkg", package = "fly"))
#> Reading layer `photo_centroids' from data source
#> `/home/runner/work/_temp/Library/fly/testdata/photo_centroids.gpkg'
#> using driver `GPKG'
#> Simple feature collection with 20 features and 16 fields
#> Geometry type: POINT
#> Dimension: XY
#> Bounding box: xmin: -126.7631 ymin: 54.34512 xmax: -126.449 ymax: 54.47635
#> Geodetic CRS: WGS 84
aoi <- sf::st_read(system.file("testdata/aoi.gpkg", package = "fly"))
#> Reading layer `aoi' from data source
#> `/home/runner/work/_temp/Library/fly/testdata/aoi.gpkg' using driver `GPKG'
#> Simple feature collection with 1 feature and 0 fields
#> Geometry type: MULTIPOLYGON
#> Dimension: XY
#> Bounding box: xmin: -126.75 ymin: 54.34813 xmax: -126.45 ymax: 54.47
#> Geodetic CRS: WGS 84
photos_12k <- centroids[centroids$scale == "1:12000", ]
selected <- fly_select(photos_12k, aoi, mode = "all")
#> Spherical geometry (s2) switched off
#> although coordinates are longitude/latitude, st_union assumes that they are
#> planar
#> although coordinates are longitude/latitude, st_intersects assumes that they
#> are planar
#> Selected 10 of 10 photos intersecting the AOI
#> Spherical geometry (s2) switched on
fly_overlap(selected)
#> Spherical geometry (s2) switched off
#> Spherical geometry (s2) switched on
#> # A tibble: 8 × 5
#> photo_a photo_b overlap_km2 pct_of_a pct_of_b
#> <int> <int> <dbl> <dbl> <dbl>
#> 1 699370 699365 2.05 27.2 27.2
#> 2 699370 699373 0.134 1.8 1.8
#> 3 699426 699425 4.56 60.6 60.6
#> 4 699426 699393 0.027 0.4 0.4
#> 5 699396 699393 0.246 3.3 3.3
#> 6 699396 699421 1.5 19.9 19.9
#> 7 699419 699421 1.46 19.4 19.4
#> 8 699425 699393 0.747 9.9 9.9