如何将Sonar测深数据叠加至OSM湖泊底图并生成等深线？

一、图层合并实现方法 #

你之前的问题在于将底图和测深点分为两个独立的ggplot对象，只需在同一个ggplot调用中叠加图层即可，同时注意使用coord_sf保证坐标系匹配（OSM数据默认采用WGS84坐标系，即EPSG:4326，与你的CSV经纬度数据一致）。

完整代码如下：

# 加载所需包
library(ggplot2)
library(osmdata)
library(sf)

# 读取测深数据
Sonar_13_07_1 <- read.csv("Sonar_13_07_1.csv")

# 定义边界范围
x_coords <- c(-3.109, -3.117)
y_coords <- c(39.817, 39.832)

# 获取OSM湖泊底图
bounding_box <- matrix(nrow = 2, ncol=2, byrow = T,
                       data = c(x_coords, y_coords),
                       dimnames = list(c("x", "y"), c("min", "max")))
osm_water_sf <- osmdata::opq(bbox = bounding_box) %>% 
  osmdata::add_osm_feature(key = 'natural', value = 'water') %>% 
  osmdata::osmdata_sf()

# 叠加底图与测深点
ggplot() +
  # 绘制OSM湖泊底图
  geom_sf(data = osm_water_sf$osm_polygons, color = "blue", fill = "lightblue") +
  # 绘制测深点，颜色映射水深
  geom_point(data = Sonar_13_07_1, aes(x = longitude, y = latitude, colour = waterDepthM), 
             size = 0.5, alpha = 0.7) +  # 调小尺寸和透明度避免遮挡
  # 设置坐标系与范围
  coord_sf(xlim = x_coords, ylim = y_coords, crs = 4326) +
  # 使用色盲友好的颜色主题
  scale_color_viridis_c(option = "plasma", name = "水深(m)") +
  # 添加标签与主题
  labs(x = "经度", y = "纬度", title = "湖泊测深点与OSM底图叠加") +
  theme_minimal()

二、生成湖泊等深线 #

基于你的测深数据，可通过两种方式生成等深线：直接使用原始数据绘制，或先插值平滑后绘制。

1. 直接用原始数据绘制等深线 #

适合数据密度较高的情况（你的3万行数据足够）：

ggplot() +
  geom_sf(data = osm_water_sf$osm_polygons, color = "blue", fill = "lightblue") +
  # 绘制填充式等深线
  geom_contour_filled(data = Sonar_13_07_1, aes(x = longitude, y = latitude, z = waterDepthM), 
                      alpha = 0.6) +
  # 可选：叠加测深点
  geom_point(data = Sonar_13_07_1, aes(x = longitude, y = latitude, colour = waterDepthM), 
             size = 0.3, alpha = 0.5) +
  coord_sf(xlim = x_coords, ylim = y_coords, crs = 4326) +
  scale_fill_viridis_d(option = "plasma", name = "水深(m)") +
  scale_color_viridis_c(option = "plasma", name = "水深(m)") +
  labs(x = "经度", y = "纬度", title = "湖泊等深线与底图叠加") +
  theme_minimal()

2. 插值平滑后绘制等深线 #

若原始数据分布不均，可先插值生成栅格数据，得到更平滑的等深线：

# 额外加载插值包
library(interp)
library(tidyr)

# 对测深数据进行插值
interp_data <- interp(Sonar_13_07_1$longitude, Sonar_13_07_1$latitude, Sonar_13_07_1$waterDepthM,
                      xo = seq(min(x_coords), max(x_coords), length.out = 500),  # 经度方向500个点
                      yo = seq(min(y_coords), max(y_coords), length.out = 500))  # 纬度方向500个点

# 转换为ggplot可用的数据框格式
interp_df <- as.data.frame(interp_data) %>%
  pivot_longer(cols = -x, names_to = "y", values_to = "waterDepthM") %>%
  mutate(y = as.numeric(y))

# 绘制平滑等深线
ggplot() +
  geom_sf(data = osm_water_sf$osm_polygons, color = "blue", fill = "lightblue") +
  geom_contour_filled(data = interp_df, aes(x = x, y = y, z = waterDepthM), alpha = 0.6) +
  coord_sf(xlim = x_coords, ylim = y_coords, crs = 4326) +
  scale_fill_viridis_d(option = "plasma", name = "水深(m)") +
  labs(x = "经度", y = "纬度", title = "平滑湖泊等深线与底图叠加") +
  theme_minimal()

内容的提问来源于stack exchange，提问作者Pere Ferriol