R 我怎样才能从 Overpass API 获得唯一的方式并减少数据量

Question

我正在尝试减少查询天桥服务器所需的数据量和时间。我只对使用 osmdata 包的方法感兴趣，这是我目前的方法：

library(osmdata)

bbox_dimensions <-c(xmin=11.2360151977671, ymin= 47.8047832575026, xmax= 11.8886729361838, ymax=48.2426118570748)

my_osm_data <- opq(bbox = bbox_dimensions,timeout = 180,memsize = 104857600) %>%
    add_osm_feature(
      key = 'highway', 
     value = c("primary","secondary", "tertiary")
      
    ) %>% 
  osmdata_sf(quiet = FALSE)

是否可以减少本次查询的数据量？我只对方式感兴趣，对沿途的节点不感兴趣。

Answer 1

正如我在评论中所写，如果您需要运行对属于同一地理区域的 OSM 数据进行多次查询，我建议采用以下方法。

首先，加载包

library(sf)
#> Linking to GEOS 3.9.0, GDAL 3.2.1, PROJ 7.2.1
library(osmextract)
#> Data (c) OpenStreetMap contributors, ODbL 1.0. https://www.openstreetmap.org/copyright.
#> Check the package website, https://docs.ropensci.org/osmextract/, for more details.
library(tmap)
tmap_mode("view")
#> tmap mode set to interactive viewing

定义 bbox 并转换为 sfc 对象（参见 github 上的讨论）：

my_bbox <- st_bbox(
  c(xmin = 11.2360151977671, ymin = 47.8047832575026, xmax = 11.8886729361838, ymax = 48.2426118570748), 
  crs = 4326
)
my_bbox_poly <- st_as_sfc(my_bbox)

然后我们需要为应该涵盖您所有查询的特定地理区域下载 OSM 提取。如果您在德国处理数据，那么我建议您检查 geofabrik 和 bbbike 提供商：

oe_match(my_bbox_poly, provider = "geofabrik")
#> The input place was matched with multiple geographical areas.
#> Selecting the smallest administrative unit. Check ?oe_match for more details.
#> $url
#> [1] "https://download.geofabrik.de/europe/germany/bayern/oberbayern-latest.osm.pbf"
#> 
#> $file_size
#> [1] 185338670
oe_match(my_bbox_poly, provider = "bbbike")
#> $url
#> [1] "https://download.bbbike.org/osm/bbbike/Muenchen/Muenchen.osm.pbf"
#> 
#> $file_size
#> [1] 58400897

bbbike 提供者返回的提取比 geofabrik 返回的提取小得多；因此，我将运行使用 bbbike.

返回的 OSM 数据执行以下步骤

oe_get("Muenchen", provider = "bbbike", download_only = TRUE, skip_vectortranslate = TRUE)
#> The input place was matched with: Muenchen
#> File downloaded!
#> [1] "C:\Users\Utente\Documents\osm-data\bbbike_Muenchen.osm.pbf"

那么，如果你想读入属于特定bbox且具有某些特征的行数据，那么我建议采用以下方法：

lines_v1 <- oe_get(
  place = "Muenchen", # or place = my_bbox_poly
  layer = "lines", 
  provider = "bbbike", 
  query = "SELECT * FROM lines WHERE highway IN ('primary', 'secondary', 'tertiary')", 
  wkt_filter = st_as_text(my_bbox_poly) 
)
#> The input place was matched with: Muenchen
#> The chosen file was already detected in the download directory. Skip downloading.
#> Start with the vectortranslate operations on the input file!
#> 0...10...20...30...40...50...60...70...80...90...100 - done.
#> Finished the vectortranslate operations on the input file!
#> Reading layer `lines' from data source `C:\Users\Utente\Documents\osm-data\bbbike_Muenchen.gpkg' using driver `GPKG'
#> Simple feature collection with 13032 features and 9 fields
#> Geometry type: LINESTRING
#> Dimension:     XY
#> Bounding box:  xmin: 11.19608 ymin: 47.80002 xmax: 11.89542 ymax: 48.25359
#> Geodetic CRS:  WGS 84

请注意，该功能会识别您已经下载了 OSM 提取并跳过再次下载同一文件。如果您设置持久下载目录，则可以优化此过程。有关详细信息，请参阅 here。

# Check result
tm_shape(my_bbox_poly) + 
  tm_borders(col = "darkred") + 
tm_shape(lines_v1) + 
  tm_lines(lwd = 2)

一种更有效（但更棘手）的方法如下：

lines_v2 <- oe_get(
  place = "Muenches", 
  layer = "lines", 
  provider = "bbbike", 
  vectortranslate_options = c(
    "-f", "GPKG", 
    "-overwrite", 
    "-where", "highway IN ('primary', 'secondary', 'tertiary')", 
    "-clipsrc", st_as_text(my_bbox_poly), 
    "-nlt", "PROMOTE_TO_MULTI",
    "lines"
  )
)
#> The input place was matched with: Muenchen
#> The chosen file was already detected in the download directory. Skip downloading.
#> Start with the vectortranslate operations on the input file!
#> 0...10...20...30...40...50...60...70...80...90...100 - done.
#> Finished the vectortranslate operations on the input file!
#> Reading layer `lines' from data source `C:\Users\Utente\Documents\osm-data\bbbike_Muenchen.gpkg' using driver `GPKG'
#> Simple feature collection with 13027 features and 9 fields
#> Geometry type: MULTILINESTRING
#> Dimension:     XY
#> Bounding box:  xmin: 11.23602 ymin: 47.80478 xmax: 11.88867 ymax: 48.24261
#> Geodetic CRS:  WGS 84

图形检查

# Check result
tm_shape(my_bbox_poly) + 
  tm_borders(col = "darkred") + 
tm_shape(lines_v2) + 
  tm_lines(lwd = 2)

^{由 reprex package (v1.0.0)}

于 2021-03-31 创建

总结：

如果您需要多次导入 OSM 数据，那么您应该 persistent download directory。这也意味着您不需要每次运行新查询时都下载 OSM 提取（除非请求的数据不包含在任何现有提取中）。
如果您需要导入覆盖 medium/small 地理区域的 OSM 线路，我建议采用“查询”方法（即 lines_v1）。
第二种方法有几个好处（即它比另一种方法更快，特别是对于较大的提取物，而且，正如您从上一个图中看到的那样，它剪裁线而不是选择与框相交的道路） .另一方面，从头开始编写 vectortranslate 选项是相当困难的（我们正在研究更直观的 API，但目前还处于开发阶段）。此外，该选项修改了 .gpkg 文件（可能有 relevant consequences）的底层结构。我们正在努力解决这两个问题，但您需要等到 0.3 或 0.4 版本。

查看 here, here, and here 了解 osmextract 背后的更多详细信息。

如有任何问题或评论，请随时在此处添加。

R 我怎样才能从 Overpass API 获得唯一的方式并减少数据量

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