Fix misaligned tiles #33
Merged
Conversation
This file contains 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
The further user is zoomed in, the less need there is to perform additional calculations to account for the curvature of the Earth, so can do a direct resampling.
arlowhite
approved these changes
Oct 2, 2024
| return resampled | ||
| end | ||
| # Helper functions for Web Mercator projection | ||
| _lat_to_y(lat::Float64) = log(tan(π / 4 + lat * π / 360)) |
There was a problem hiding this comment.
these don't already exist in a geo library?
There was a problem hiding this comment.
I was interacting with GDAL via Rasters.jl and the performance hit was very significant (talking minutes).
I could potentially call out to GDAL.jl directly, but I think it would be doing extra things we don't need for our immediate use case.
Mark as future improvement?
There was a problem hiding this comment.
Would this still be needed if we switched to web-mercator for all the data in the future?
|
This PR requires changes to the project so please don't forget to |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
Previously, when loading tiles for display, the far north and south of each region were misaligned when sufficiently zoomed out.
This is because the method previously applied was incorrectly handling curvature of the earth.
The issue would go away when sufficiently zoomed in because an alternate, faster, approach was being applied at that zoom level when no adjustment for earth's curvature was needed (a detail I had forgotten).
I've now replaced the previous approach with a more accurate one, and also replaced the "fast" approach with an image resizing method already implemented in a package dependency (Images.jl), which turns out to be much faster than my own implementation.
Rough comparison for the same area:
Before:
After: