Add terrain correction in spherical coordinates to the User Guide - #700
Open
manduinca wants to merge 1 commit into
Open
Add terrain correction in spherical coordinates to the User Guide#700manduinca wants to merge 1 commit into
manduinca wants to merge 1 commit into
Conversation
Add a section to the topographic correction guide showing how to forward model the topographic masses with a tesseroid layer in geocentric spherical coordinates: build the layer from the topography grid using radii, express the observation points consistently with the layer, clamp their radii so every computation point falls outside the tesseroids, and compute the topography-free gravity disturbance.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Closes #353
Adds a section to the topographic correction guide showing how to forward model the topographic masses with a tesseroid layer in geocentric spherical coordinates, mirroring the existing Cartesian workflow: build the layer from the topography grid using radii, express the observation points consistently with the layer (geodetic latitude +
geocentric_radius(latitude) + height), and compute the topography-free gravity disturbance.One design question I'd like your input on: since the observations sit on the terrain, some fall slightly below the top of their tesseroid, and
tesseroid_gravityrequires computation points outside the tesseroids. I clamp their radii against the maximumtopwithin a 3x3 neighborhood (robust for stations right on cell boundaries), which lifts ~2600 of the 3877 stations (most by a few meters, worst case ~670 m in rugged cells). Checking against the Cartesian result, stations that don't get lifted differ by ~4 mGal rms (method difference), while heavily lifted ones can differ much more. Happy to switch to clamping against each station's own cell top (minimal lift) or another approach if you prefer.I couldn't build the docs locally (missing GMT binary for PyGMT), but the code of the new section runs end-to-end (~30 s for the tesseroid forward).