gather information about vertical datum from USGS stations

[carolakaiser]

Hey All,
As discussed in our meeting, we have been asked to explore the possibility of adding USGS stations for the US Pacific Coast. This will very likely be a larger number of stations and your service to retrieve USGS stations is very helpful. Thank you for that!
Would it be possible to get any information about the vertical datum for each USGS station? The USGS website has this info in but it requires manual work to get this info. Any way to get this in an automated way would be very much appreciated!
Thank you.

[brey]

@SorooshMani-NOAA from the meeting, some relevant quantities

Gage height: 00065,
Stream (NAVD88) 63160,
Ocean (NAVD88): 62620,
62615 Elevation, lake/res, NAVD88 62614 Elevation, lake/res NGVD29, 63158 Stream level NGVD29

[SorooshMani-NOAA]

This will be at least partially addressed by #65