Topographic Database (pl. Baza Danych Obiektów Topograficznych) is a vector (object) database containing the spatial location of topographic objects with their characteristics for Poland. The content and detail of the database correspond to the topographic map in the scale 1:10000. The thematic scope includes information on water network, communication network, land cover, buildings and technical structures, utility infrastructure, land use, protected areas, territorial division units, and other objects. The database is available in the Geography Markup Language (GML) format. The source of its data comes from:
The purpose of this vignette is to perform spatial operations on vector data from the Topographic Database. We focus on four cases, taking into account different types of geometry, i.e. point, line, and polygon, and their attributes. Also, we show how they can be visualized.
Our analysis area is the bieszczadzki county located in the Subcarpathian (podkarpackie) voivodeship. It is the farthest south area in Poland that also has the lowest population density (19 people on km2).
We start by downloading the topographic database for our county using the
# 22.4 MB topodb_download("bieszczadzki", outdir = "./data")
If you run into any problem with the download, remember that you can pass another download method from
download.file() as a function argument.
topodb_download(req_df, outdir = "./data", method = "wget")
The downloaded database consists of many files in the GML format. All the data necessary for analyzes can be found in the
data/PL.PZGiK.332.1801/BDOT10k/ location. A brief description of the structure of this database can be found here.
First, let’s load the file with administrative units ("PL.PZGiK.332.1801__OT_ADJA_A.xml") using the sf package and its
territory = read_sf("data/PL.PZGiK.332.1801/BDOT10k/PL.PZGiK.332.1801__OT_ADJA_A.xml")
The file contains administrative units at various levels, let’s choose the lowest level, i.e. communes. There are three types of communes in this dataset, specified in the
rodzaj column: urban (GM), rural (GW), and urban-rural (Gmw). Let’s select them.
## ## Gmw GW ## 1 2
We can see that the bieszczadzki county consists of two rural communes and one urban-rural commune. Let’s visualize it.
plot(communes, axes = TRUE, main = "Bieszczadzki county")
In the first task, we calculate the lengths of roads, taking into account their categories. Road data can be found in the "PL.PZGiK.332.1801__OT_SKDR_L.xml" file.
roads = read_sf("data/PL.PZGiK.332.1801/BDOT10k/PL.PZGiK.332.1801__OT_SKDR_L.xml")
Let’s plot them. We use the
plot() function again, but this time we combine the two layers into one image. The first layer (in the background) contains roads and to add another layer, we have to set the argument
"FALSE". Then we can add a second layer with the territory borders by setting the
add argument to
plot(roads["katZarzadzania"], main = "Road category", reset = FALSE) plot(st_geometry(territory), add = TRUE)
We have six road categories related to the managing entity. Those are: national (K), voivodeship (W), county (P), communal (G), institutional (Z), and other (I) roads.
We use the
st_length() function to find the length of each object in the table. Next, we create a data frame consisting of the road category and its length. Then we aggregate this data frame and calculate the sum of the lengths for each category.
length_roads = st_length(roads) length_roads = data.frame(length = length_roads, class = as.factor(roads$katZarzadzania)) length_roads = aggregate(length ~ class, data = length_roads, FUN = sum)
The results are given in meters - let’s convert them into kilometers.
# convert to [km] length_roads$length = units::set_units(length_roads$length, "km")
Let’s also change the names of the categories.
Now we can see the results. The
other type of roads dominates that consists mainly of non-public roads.
## class length ## 1 communal 186.17329 [km] ## 2 other 2819.55806 [km] ## 3 national 19.24996 [km] ## 4 county 187.17870 [km] ## 5 voivodeship 105.67567 [km] ## 6 institutional 10.44893 [km]
We can also calculate the total length of the roads in this area.
## 3328.285 [km]
The result is about 3328.285 km. Another aspect of the data that we can investigate is the density of the road network. We need to calculate the total area first, and then divide the total road length by the total area.
## 2.921031 [km/km2]
The road density is about 2.92 km/km2.
Another dataset included in the Topographic Database contains rivers for this area ("PL.PZGiK.332.1801__OT_SWRS_L.xml").
rivers = read_sf("data/PL.PZGiK.332.1801/BDOT10k/PL.PZGiK.332.1801__OT_SWRS_L.xml") rivers = rivers[rivers$rodzaj == "Rz", ] # select only rivers
Rivers are divided into smaller sections with different parameters, such as river width or data source. Let’s merge sections from the same rivers into a single feature (geometry) - we can use the attribute with an ID (
idMPHP) for that purpose. We can also give each river a category number by creating a sequence from 1 to n using the
Let’s visualize the rivers’ courses.
With rivers and roads, we can designate points of intersection that symbolize bridges and crossings. We can use the
st_intersection() function for this.
##  81
We get 81 such points. Let’s plot them.
# use 'dev.off()' to reset previous plot plot(st_geometry(rivers), main = "Bridges and crossings", col = "blue") plot(st_geometry(territory), add = TRUE) plot(bridges, add = TRUE, pch = 20)
Land cover is the physical material at the surface of the earth like grass, trees, bare ground, water, etc. Let’s check the land cover data for our county - it is stored in files with the
PT prefix. We use the
list.files() function to list them. The
pattern argument is important here because it determines what files should be selected. Our
pattern should look like this:
PT+.+A\\.xml$ - only files containing areal data (A) of land cover (PT) will be listed.
files = list.files("data/PL.PZGiK.332.1801/BDOT10k", pattern = "PT+.+A\\.xml$", full.names = TRUE) # print filenames basename(files)
##  "PL.PZGiK.332.1801__OT_PTGN_A.xml" ##  "PL.PZGiK.332.1801__OT_PTKM_A.xml" ##  "PL.PZGiK.332.1801__OT_PTLZ_A.xml" ##  "PL.PZGiK.332.1801__OT_PTNZ_A.xml" ##  "PL.PZGiK.332.1801__OT_PTPL_A.xml" ##  "PL.PZGiK.332.1801__OT_PTRK_A.xml" ##  "PL.PZGiK.332.1801__OT_PTSO_A.xml" ##  "PL.PZGiK.332.1801__OT_PTTR_A.xml" ##  "PL.PZGiK.332.1801__OT_PTUT_A.xml" ##  "PL.PZGiK.332.1801__OT_PTWP_A.xml" ##  "PL.PZGiK.332.1801__OT_PTWZ_A.xml" ##  "PL.PZGiK.332.1801__OT_PTZB_A.xml"
We also can exclude "PL.PZGiK.332.1801__OT_PTSO_A.xml" file from the list, because this file contains zero objects (features).
# drop "OT_PTSO_A.xml" files = files[-7]
Let’s prepare the names of the objects to which the data will be loaded. The following names are the extended names of the abbreviations stored in the filenames.
layer_names = c("fallowlands", "communication", "forest", "undeveloped", "squares", "shrublands", "crops", "grassland", "water", "heaps", "buildings")
Now we load each GML file, naming it from the list above. Instead of using a loop, we can use the
lapply() function, which performs a specific action for each element of the vector. The action in our case is to load the GML files using
Previously, we used
st_length() to calculate the line length, now we use corresponding
st_area() function to calculate the area. Here we use the
lapply() function analogously, which will work for each item on the list. A similar function is
sapply(), which returns a vector instead of a list.
# calculate areas in each layer area_landcover = lapply(layers, st_area) # sum areas for each layer area_landcover = sapply(area_landcover, sum) # convert units area_landcover = units::set_units(area_landcover, "m^2") area_landcover = units::set_units(area_landcover, "km^2") names(area_landcover) = layer_names
Let’s see the results (in kilometers).
## Units: [km^2] ## fallowlands communication forest undeveloped squares ## 0.07561383 1.97014481 860.17248134 0.27817715 0.29038385 ## shrublands crops grassland water heaps ## 1.57266555 255.13528884 0.63447491 8.81181550 0.09220115 ## buildings ## 10.38781092
Let’s make sure that the total land cover is equal to the area of our county. Some tiny precision differences are possible, so we should set the difference tolerance. This is possible using the
##  TRUE
Everything is correct. Let’s present the results as percentages of the area and sort them in descending order.
## forest crops buildings water communication ## 75.49 22.39 0.91 0.77 0.17 ## shrublands grassland squares undeveloped heaps ## 0.14 0.06 0.03 0.02 0.01 ## fallowlands ## 0.01
Over 75% of the county’s area is covered by forests and only less than 1% by buildings.
In the last analysis in this vignette, we want to check how many buildings have bus stops within a given distance. We can apply spatial buffers to solve this question. Information about bus stops is in the "PL.PZGiK.332.1801__OT_OIKM_P.xml" file, where they are represented by the OIKM04 value of the
bus_stop = read_sf("data/PL.PZGiK.332.1801/BDOT10k/PL.PZGiK.332.1801__OT_OIKM_P.xml") bus_stop = bus_stop[bus_stop$x_kod == "OIKM04", ]
Let’s prepare a visualization in which the bus stops are marked with blue dots and the buildings are presented as red polygons.
buildings = layers$buildings plot(st_geometry(communes), main = "Bus stops") plot(st_geometry(layers$buildings), add = TRUE, border = "red") plot(st_geometry(bus_stop), add = TRUE, pch = 20, cex = 0.7, col = "blue")
Let’s create a buffer for each bus stop with a range of 1 km using
bus_buffer = st_buffer(bus_stop, 1000)
Now, we can plot it all.
plot(st_geometry(communes), main = "Bus stops buffers") plot(st_geometry(buildings), add = TRUE, border = "red") plot(st_geometry(bus_buffer), add = TRUE)
To return the buildings within the buffer range, we can perform the
buildings_buffer = st_within(buildings, bus_buffer)
The result is a nested list that consists of 2828 buildings and their associated buffers. Let’s count how many buildings are not in any buffer by using
sapply() as in the previous examples.
##  14
Answer to our last question: 14% of the buildings in this county do not have access to a bus stop within a 1 km radius.