title: Extracting the sensing date/time over a particular lat/lng in a netCDF file in python
body: <p>I am currently working with multiple netCDF files in python. I am using Sentinel-5P NO2 tropospheric columns over Greater London. I want to plot the individual files as a time series, titled with the passover time over London for each individual swath but I am unsure as how to extract this.</p>
  <p>Is there a simple way to which I can extract the passover time of the satellite over a particular lat/lng for each file?</p>
  <p>EDIT:
  Some more information on the files. They are netCDF files meaning they contain Dimensions, Variables, Attributes and Coordinates. They contain information on Vertical Column Densities of NO2 over London at a spatial resolution of 3.5x7km. I have opened the files with xarray in PyCharm and have further attached an image to provide more information on the variables.</p>
  <p><a href="https://i.stack.imgur.com/laY27.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/laY27.png" alt="enter image description here" /></a></p>
  <p>I essentially need to find the value of delta_time when latitude=51.2 or 51.8. Below is what I have developed so far, however I have around 50 files all with over 100,000 pixels so this is very very slow. Does anyone know how I can improve this?</p>
  <pre><code>
      for i in file_list:
  
          # Open product - GROUP PRODUCT
          with xr.open_dataset(i, group='PRODUCT') as file:
              print(colored('\nPRODUCT Group:\n', 'blue'), file)
  
          no2 = file['nitrogendioxide_tropospheric_column'][0]
  
          for row in no2.coords['latitude']:
              for cell in row:
                  if cell == 51.2 or cell == 51.8:
                      print(cell)
                      print(cell['scanline'])
                      scanpoint = (cell['scanline'])
                      scantime = no2['delta_time'].sel(scanline=scanpoint)
                      print(scantime)
                      return scantime
              else:
                  continue
  </code></pre>