From e373c6383713967cb2e4769c127fc2e543691dcf Mon Sep 17 00:00:00 2001 From: Tom Hughes Date: Tue, 23 Oct 2007 09:19:29 +0000 Subject: [PATCH] Round latitude and longitude values in links to a sensible number of decimal places for the zoom level whilst still preserving accuracy sufficient to position the map within a few pixels. The relationship between zoom level, decimal places, and the accuracy with which the map can then be positioned in pixels is as follows: Zoom Decimals Accuracy (pixels) 1 0 1.42 2 0 2.84 3 1 0.57 4 1 1.14 5 1 2.28 6 2 0.46 7 2 0.91 8 2 1.82 9 3 0.36 10 3 0.73 11 3 1.46 12 4 0.29 13 4 0.58 14 4 1.17 15 5 0.23 16 5 0.47 17 5 0.93 18 6 0.19 So the worse case is at zoom 2 where accuracy is still within 3 pixels. Based on a patch by rjmunro. --- public/javascripts/site.js | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/public/javascripts/site.js b/public/javascripts/site.js index 95ef1f536..b1690b7d1 100644 --- a/public/javascripts/site.js +++ b/public/javascripts/site.js @@ -1,6 +1,20 @@ function updatelinks(lon,lat,zoom,layers) { + var decimals = Math.pow(10, Math.floor(zoom/3)); var node; + lat = Math.round(lat * decimals) / decimals; + lon = Math.round(lon * decimals) / decimals; + + node = document.getElementById("permalinkanchor"); + if (node) { + var args = getArgs(node.href); + args["lat"] = lat; + args["lon"] = lon; + args["zoom"] = zoom; + args["layers"] = layers; + node.href = setArgs(node.href, args); + } + node = document.getElementById("viewanchor"); if (node) { var args = getArgs(node.href); -- 2.43.2