Rで海岸線のプロット

国交省の国土数値情報データ(http://nlftp.mlit.go.jp/ksj/gml/datalist/KsjTmplt-C23.html)を利用し、Rで東京湾の海岸線を描くこうとしていますが、内陸の一部が黒く塗りつぶされてしまいます。

R
1#パッケージの読み込み
2library(rgdal)
3library(dplyr)
4library(broom)
5library(ggplot2)
6
7#shpファイルの読み込み
8ogrListLayers("tokyo")
9tcoast <- readOGR("tokyo", "C23-06_13-g_Coastline")
10
11ogrListLayers("kanagawa")
12kcoast <- readOGR("kanagawa", "C23-06_14-g_Coastline")
13
14ogrListLayers("chiba")
15ccoast <- readOGR("chiba", "C23-06_12-g_Coastline")
16
17#tidyへの変形
18tc <- tidy(tcoast)
19tcdata <- tcoast@data %>%
20  tibble::rownames_to_column("id") %>%
21  inner_join(tc, by = "id")
22
23kc <- tidy(kcoast)
24kcdata <- kcoast@data %>%
25  tibble::rownames_to_column("id") %>%
26  inner_join(kc, by = "id")
27
28cc <- tidy(ccoast)
29ccdata <- ccoast@data %>%
30  tibble::rownames_to_column("id") %>%
31  inner_join(cc, by = "id")
32
33#図示
34pdef <- ggplot(NULL) + 
35  coord_quickmap() + 
36  theme(panel.background = element_rect(fill = "transparent", colour = "black"),
37        panel.grid = element_blank(),
38        legend.position = "none")
39
40ptc <- geom_line(data = tcdata, aes(long, lat, group = group), color = "black")
41pkc <- geom_line(data = kcdata, aes(long, lat, group = group), color = "black")
42pcc <- geom_line(data = ccdata, aes(long, lat, group = group), color = "black")
43
44pdef + ptc + pkc + pcc + xlim(139, 141) + ylim(34.9, 35.8)