Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

add clamp for extreme lats #124

Open
wants to merge 7 commits into
base: main
Choose a base branch
from
Open

add clamp for extreme lats #124

Changes from all commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
0fa52e5
add clamp for lats beyond +/-90
May 1, 2019
71ae3da
remove extraneous line
May 1, 2019
5c5f1e8
differentiate variables for clarity
May 1, 2019
4af468c
lint
May 1, 2019
10dfcfd
apply differential clamping
May 2, 2019
2405a96
lint
May 2, 2019
acba247
clamp latitude after projection
peterqliu Aug 6, 2019
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 8 additions & 2 deletions src/convert.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,9 @@
import simplify from './simplify';
import createFeature from './feature';

const maxMercatorLatitude = 85.05;
const tileResolution = 8192;

// converts GeoJSON feature into an intermediate projected JSON vector format with simplification data

export default function convert(data, options) {
Expand Down Expand Up @@ -135,8 +138,11 @@ function projectX(x) {
return x / 360 + 0.5;
}

// clamps the rendered latitude to what's renderable on the south extreme, and what's Mercator on the north extreme

function projectY(y) {
const sin = Math.sin(y * Math.PI / 180);
const clampedY = Math.min(Math.max(y, -maxMercatorLatitude), maxMercatorLatitude);
const sin = Math.sin(clampedY * Math.PI / 180);
const y2 = 0.5 - 0.25 * Math.log((1 + sin) / (1 - sin)) / Math.PI;
return y2 < 0 ? 0 : y2 > 1 ? 1 : y2;
return Math.max(y2, (tileResolution - 1) / tileResolution);
}