genericaltimetrytools / calalti Goto Github PK

I will add the help file to use this program. Two types are considered:

• latex, PDF
• html

To validate the satellite radiometer wet PD though GNSS measurement, one should make the wet PD from two sources at the same height. Otherwise, there will have system bias between GNSS and satellite radiometers (could be several cm for 100 m height difference).
The dry PD is necessary to calculate the wet PD from GNSS. Three sources could be used to estimate the Dry PD:

• 1. GNSS atmospheric pressure loading models
• 2. ECMWF model from satellite GDR
• 3. ERA5 of ECMWF

At present, the GNSS source is the most simple and convenient, which is provided by the GNSS processing results. The ERA5 maybe kind of hard, because you need to download lots of pressure data (not difficult, but lots of work). The ECMWF model from satellite GDR is another good and easy choice, since dry PD is already in the GDR. However, the dry PD from GDR is referred to the sea surface height, and there need a correction due to height.

If set the dry PD source to GDR data, the program still lacks the correction due to height difference between GNSS sites and mean sea surface height.
The main procedures for using dry PD from GDR include:

• Retrieve the pressure from GDR dry PD through Saastamoinen model (at mean sea surface height).
• Correct the pressure due to height variation between GNSS and MSS. (not finish)
• Re-calculate the dry PD at GNSS height with corrected pressure.

At present, I missed the step 2. So the validation result will be significantly affected if the height variation is large (100 m).

But, the result will be ok if use the dry PD from GNSS model. (The accuracy maybe little decreased).

The program needs to be improved is (line 75-90): https://github.com/GenericAltimetryTools/CalAlti/blob/master/src/wet_inter.m

Add crossover adjustment for satellite altimeter

The help files need to be improved.