Protocolbuffer Binary Format (PBF) Documentation or Examples?

TomNeer

ArcGIS Enterprise added support for the PBF output format in 10.7.1. We are having difficulty finding any documentation or examples on Esri's implementation of PBF in either the Developer's documentation or Esri's Github outside of Vector Tiles. We would like to look at using this format with some larger datasets. Any pointers would be appreciated? 

JINANYI

I read the references you provided and also this article: FAQ: What is a root tile and how are they used to make a vector tile package with a local coordinate system? https://support.esri.com/en/technical-article/000022396

Using all the info, I tried to decode the a vector tile myself, using World Topographic Map (https://basemaps.arcgis.com/arcgis/rest/services/World_Basemap_v2/VectorTileServer). I downloaded this particular tile in pbf, https://basemaps.arcgis.com/arcgis/rest/services/World_Basemap_v2/VectorTileServer/tile/6/24/17, and start decoding in R language (sorry it's the only language I know).

However, as it turned out, for some unknown reason, the origin of the selected tile seems to be the bottom left corner (x axis positive to the right, y axis positive upward), instead of top left corner. It is shown in the following codes:

 

 

```{r}
library(sf)
librart(ggplot2)

#the st_read() function automatically uses `MVT' driver, and convert the geometry data into tile coordinates
test <- st_read("17.pbf", layer = "City small scale")

#function that convert tile coordinates into the real mapping coordinates (EPSG: 3857)
shift_tile_coord <- function(sf, level, row, column, crs = 3857) {
    if(crs != 3857) stop("currently only supports EPSG:3857 Web Mercator projection")

    origin_x <- -20037508.342787
    origin_y <- 20037508.342787
    maxscale <- 2.958287637957775E8
    tile_size <- 512 #pixels of a row/ column
    dpi <- 96
    inch2mapUnit <- 39.3700787  #1 meter = 39.3700787 inch
    tile_extent <- 4096

    root_tile_width <- maxscale * (tile_size/(dpi * inch2mapUnit))
    selected_tile_width <- root_tile_width/2^level
    
    sf_shifted <- sf
    
    #x = tile_x_coor*selected_tile_width/tile_extent + origin_x + selected_tile_width*column
    #y = tile_y_coor*selected_tile_width/tile_extent + origin_y - selected_tile_width*(row + 1)
    sf_shifted$geometry <- sf$geometry * matrix(c(selected_tile_width/tile_extent, selected_tile_width/tile_extent), ncol = 2)
    sf_shifted$geometry <- sf_shifted$geometry + matrix(c(origin_x + selected_tile_width * column, origin_y - selected_tile_width * (row + 1)), ncol = 2)
    
    sf_shifted <- st_set_crs(sf_shifted, crs)
    
    return(sf_shifted)
}

#visulaize the data
test_shifted <- shift_tile_coord(test, level = 6, row = 24, column = 17)

ggplot(data = test_shifted) + 
    geom_sf_label(aes(label = X_name_en)) +
    geom_sf() +
    coord_sf(datum = st_crs(3857))
```

 

 

 

Test Data

 

If you use map viewer to check (https://www.arcgis.com/apps/mapviewer/index.html?layers=7dc6cea0b1764a1f9af2e679f642f0f5#), the coordinates (in Web Mercator, EPSG: 3857) are correct. However, the conversion of a y coordinate = tile_y_coor*selected_tile_width/tile_extent + origin_y - selected_tile_width*(row + 1). This means a y coordinate first starts at the bottom of the tile (thus (row + 1)), and moves upward (positive sign in tile_y_coor*selected_tile_width/tile_extent). This seems to be against the documentation you provided. Is it designed to be this way, or is there something wrong?

@mgeorge