MVT fields/geometry alignment

[mdsumner]

Example MVT:

# https://docs.mapbox.com/vector-tiles/reference/
#token <- ceramic::get_api_key()
token <- YOUR_TOKEN
u <- "http://a.tiles.mapbox.com/v4/mapbox.mapbox-streets-v7/14/4823/6160.mvt?access_token={token}"

curl::curl_download(glue::glue(u), "6160.mvt")

# ceramic$ ogrinfo 6160.mvt
# INFO: Open of `6160.mvt'
#       using driver `MVT' successful.
# 1: landuse (Multi Polygon)
# 2: waterway (Line String)
# 3: water (Multi Polygon)
# 4: aeroway (Polygon)
# 5: barrier_line
# 6: building (Multi Polygon)
# 7: landuse_overlay (Polygon)
# 8: road
# 9: admin (Line String)
# 10: place_label (Point)
# 11: rail_station_label (Point)
# 12: poi_label (Point)
# 13: motorway_junction (Point)
# 14: road_label (Multi Line String)
# 15: waterway_label (Line String)

There are 81 geometries, and 81 names, but 85 rows of fields. The last rows of field values are "".

This seems to be a reliable way to match geometries to rows, not sure if names may interspersed.

sf fails to read

## bring the empty rows to the top with arrange

as_tibble(vapour_read_attributes("6160.mvt", layer = 0)) %>% arrange(class)
# A tibble: 85 x 3
   mvt_id class    type     
    <dbl> <chr>    <chr>    
 1      0 ""       ""       
 2      0 ""       ""       
 3      0 ""       ""       
 4      0 ""       ""       
 5      0 cemetery christian
 6      0 cemetery christian
 7      0 cemetery christian
 8      0 grass    grass    
 9      0 grass    grass    
10      0 grass    grass    
# … with 75 more rows


## 81 geometries 
str(vapour_read_geometry("6160.mvt", layer = 0))
List of 81
 $ : raw [1:550] 01 06 00 00 ...
 $ : 

# 81 names

vapour_read_names("6160.mvt")
 [1]  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
[34] 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
[67] 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

[mdsumner]

vapour is ignoring NULL geometries, and it should not do that