可视化特定国家/地区的MODIS植被层(使用R-package MODISttsp) [英] Visualising MODIS Vegetation layers for a specific country (using R-package MODISttsp)

问题描述

我正在尝试下载和可视化肯尼亚(以及其他类似国家)的NDVI数据.

I am trying to download and visualise the NDVI data in Kenya (and other countries similarly).

为此，我使用 osmdata 检索了肯尼亚的边界框，并在从 MODIStsp

For this, I retrieved the bounding box for Kenya using osmdata and used this when downloading NDVI data from MODIStsp

library(osmdata)
library(MODIStsp)

kenya_bb <- osmdata::getbb("Kenya")

MODIStsp(gui             = FALSE,
         out_folder      = "Data",
         out_folder_mod  = "Data",
         selprod         = "Vegetation_Indexes_16Days_1Km (M*D13A2)",
         bbox            =  kenya_bb,
         bandsel         = "NDVI",
         user            = "mstp_test" ,
         password        = "MSTP_test_01",
         start_date      = "2020.06.01", 
         end_date        = "2020.06.15", 
         verbose         = FALSE)

然后我只是简单地查看了下载的数据，但似乎并没有裁剪出肯尼亚

Then I simply visualised the downloaded data, but it hasn't seemed to crop out Kenya

library(raster)
library(here)
library(ggplot2)

NDVI_raster <- raster(here::here("Data/VI_16Days_1Km_v6/NDVI/MOD13A2_NDVI_2020_161.tif"))

NDVI_df <- as.data.frame(NDVI_raster, xy = TRUE, na.rm = TRUE)
rownames(NDVI_df) <- c()

ggplot(data = NDVI_df,
       aes(x=x,y=y)) +
  geom_raster(aes(fill = MOD13A2_NDVI_2020_161))

任何关于如何种植单个国家的想法都受到赞赏

Any ideas on how to crop out single countries are appreciated

推荐答案

此行为的原因是参数 spatmeth 的默认值为"tiles" ，因此，使用参数 start_x ， end_x ， start_y 和 end_y 指定的值(如果未明确指定，则为其默认值)).

The reason of this behaviour is that the default value of argument spatmeth is "tiles", so values specified with arguments start_x, end_x, start_y and end_y (and, if not explicitly specified, their defaults) are used.

从功能文档中获取:

bbox 数字(4)out_proj坐标系中的输出边界框(xmin，ymin，xmax，ymax).是否忽略spatmeth =="tiles" ，默认值:NULL

bbox numeric(4) Output bounding box (xmin, ymin, xmax, ymax) in out_proj coordinate system. Ignored if spatmeth == "tiles", Default: NULL

spatmeth 字符["tiles"|"bbox"|文件"]，指示如何检索处理范围.如果是瓦片"，则使用指定的图块(start_x ....).如果是文件"，则从空间文件中检索范围在spafile中指定.如果是"bbox"，请使用指定的边界框，默认:"tiles"

spatmeth character ["tiles" | "bbox" | "file"], indicates how the processing extent is retrieves. if "tiles", use the specified tiles (start_x....). If "file", retrieve extent from spatial file specifies in spafile. If "bbox", use the specified bounding box, Default: "tiles"

要使用 kenya_bb 范围，您必须:

1. 添加 spatmeth ="tiles" ;
2. 正确的 bbox = kenya_bb 到 bbox = as.vector(kenya_bb)

此外，有一个影响此案的错误，最近已修复.您还应该从GitHub重新安装该软件包:

Moreover, there was a bug affecting this case, recently fixed. You should also reinstall the package from GitHub:

remotes::install_github("ropensci/MODIStsp")

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