presently this code uses a static lat lon while variable lat lon data exist, from which we should get a better elevation measurement from ATM over time.

It would not be hard to have a variable position per year using the interpolated positions

https://epic.awi.de/id/eprint/55943/

output/GC-Net_info_incl_1999.csv

https://github.com/GEUS-Glaciology-and-Climate/GCNet_positions/blob/main/output/GC-Net_info_incl_1999.csv

SWC: same coords as 1990 (within rounding), discarding
CP1: different from other coords listed there, could be real obs from missing year
NASA-U: off the main track of other coords, discarding
GITS: off the main track of other coords, discarding
HUM: same coords as 1995, discarding
SUM: different from other coords listed there, could be real obs from missing year
TUN: different from other coords listed there, could be real obs from missing year, same as metadata_2000 (below)
DY2: different from other coords listed there, could be real obs from missing year
JAR1: same as 1996, discarding
SDO: different from other coords listed there, could be real obs from missing year
NAE: different from other coords listed there, could be real obs from missing year, same as metadata_2000 (below)
NSE: different from other coords listed there, could be real obs from missing year
PET: different from other coords listed there, could be real obs from missing year
NEM: different from other coords listed there, could be real obs from missing year
EGP: different from other coords listed there, could be real obs from missing year

metadata file from 2000

https://github.com/GEUS-Glaciology-and-Climate/GC-Net-level-1-data-processing/blob/main/metadata/Gc-net_documentation_Nov_10_2000_outdated.pdf

most of the coordinates have a year of measurements, but some are left without one

Saddle: coords off-track, discarding
TUN: same as GC-Net info_incl_1999.csv
NAE: same as GC-Net info_incl_1999.csv

WMO coordinates in 2012 report

https://github.com/GEUS-Glaciology-and-Climate/GCNet_positions/blob/main/data/GC_Net_SYNOP_status20120301.pdf

SWC: somewhere between 2005 and 2006 coordinates, discarding
CP1: different from other coords listed there, could be real obs from missing year
GITS; different from other coords listed there, could be real obs from missing year
HUM: same as 1995, discarding
SUM: different from other coords listed there, could be real obs from missing year
TUN: different from other coords listed there, could be real obs from missing year
DY2: different from other coords listed there, could be real obs from missing year
JAR1: same as 2005, discarding
SDL: different from other coords listed there, could be real obs from missing year
SDO: different from other coords listed there, could be real obs from missing year
NAE: different from other coords listed there, could be real obs from missing year
NSE: off track, discarding
NEM: different from other coords listed there, could be real obs from missing year

according to the ATM data v1 user guide and the v2 data guide ATM heights are "above WGS84 ellipsoid", which I think is the same as for the single frequency GPS data compilation.

Yet, the single frequency GPS elevations are often lower than the ATM data.

Here's an example that includes both 'handheld' elevations, mainly from Koni Steffen's field notes, and monthly averages from the GEUS GC-Net data. The difference in this case is the single frequency GPS data are mostly ca. 60 m lower.

or mostly ca. 40 m lower for single frequency GPS data at Saddle

for Swiss Camp, the monthly averages of single frequency GPS data from the GEUS AWS are ca. 50 m lower. However the nearest point has moved downslope so I should search by an annually varying position.

Yet, it's not always that the single frequency GPS data are lower, e.g. Summit, below so I am thinking the single frequency data are unreliable BUT the monthly averages from single frequency should not be biased?

Find all the plots in https://github.com/GEUS-Glaciology-and-Climate/GCNet_positions/tree/main/ATM/Figs

Need to get some description of the GNSS set up from a field team member.