Slant Residual Plots
As part of the daily processing we are computing slant path residuals for selected sites is regions with a high density of sites. The slant path residuals show azimuthal and elevation variations from the zenith wet delay mapped to Line of site elevation of the satellite. We compute a multipath map by stacking the residuals from many previous solutions and subtract the multipath before generating these plots. Thus the plots represent primarily atmospheric signal. Although they are also affected by errors in the multipath map and measurement noise in the GPS delays. Keeping in step with the general color bar scheme, blue represents atmosphere drier than the mapped zenith average and red represents wetter than the zenith pwv estimate.

We are computing a direct mapping function for each site using the AVN weather model analysis prediction. Standard mapping functions tend to break down for low elevation angles, but the Direct Mapping technique works to very low angles. (Please refer to the document: "Improved Mapping of Tropospheric Delays")

Our processing is based on station differencing methods, generating differenced residuals. Line of sight residuals are generated by applying statistical constraints + a linear inversion method to the double difference residuals. (Please refer to the document: "Obtaining singlepath phase delays from GPS double differences")

Currently only Suominet sites and selected FSL sites are processed for slant residual plots.