I have a NetCDF layer file with monthly SPEI-6 values between the years 1950 and 2020 from Global Drought Monitor, a shapefile with polygons of geographical areas that I want to use for extracting values, and a point shapefile/table with the specific months and years that I want to extract values for. What is the best way to extract values from the NetCDF file at specifically defined locations and points in time? If it makes things easier, I could use points instead of polygons for the extraction.
Any guidance on how to do this in e.g. ArcGIS or Rstudio would be much appreciated.
If you want to extract a time series for a point over your study area you can use (make netcdf table view) from (multidimension tools) in arcmap, you will choose your variable, time in row dimensions and lat long from dimension value. Then export table to excel.
You might use an add in tool (NetCDF4Excel), it enables you to access all data in the time series in the familiar format of Excel. Try this link https://netcdf4excel.github.io/
The MeteoInfoLab script examples for extracting data by point locations (http://www.meteothink.org/examples/meteoinfolab/file_io/interp_st.html) and by polygon regions (http://www.meteothink.org/examples/meteoinfolab/map/ave_polygons.html).
Hi dear Patrick
If you can't apply to R and ArcGIS codes, I invite you to watch this video. It would be useful to you, and you can easily extract your data.
https://www.youtube.com/watch?v=kR4Q59WQ6og&list=PLaT4Cfntnc9jklkHwIh0tR0eGx_3BDc0k
As you know, we don't have a unique format in NC files from different sources. Each file has a various number of dimensions and attributes. Therefore it would be tough if you want to develop separate codes to apply in your different studies. According to the introduced link, you can apply various NC files from different sources, such as NOAA, many gridded datasets, CMIP6 models, etc.
If you need more help, let me know.
Cheers,
Nasrin
Many thanks Sadiya Tijjani Baba for the R code and Nasrin Salehnia for the instructive video. This was indeed very helpful!
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