<div dir="ltr">Gerg,<div><br></div><div>Once again, thank you very much for you prompt, super detailed, complete and instructive answer.</div><div><br></div><div>Best regards,</div><div><br></div><div>Alexandre</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">2015-02-28 4:45 GMT-03:00 Gerd Petermann <span dir="ltr"><<a href="mailto:gpetermann_muenchen@hotmail.com" target="_blank">gpetermann_muenchen@hotmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div dir="ltr">Hi Alexandre,<br><br>yes, simplification happens in various places. The reasons are limits in the Garmin<br>format as well as optimization of the img file size.<br><br>1) The Garmin img format uses a raster with ~2.3 m distance at resolution 24. <br>I think of it as a bed of nails, you can draw straigt lines between any of the nails.<br>Details below this resolution are removed. We use two different algos for lines and shapes <br>here, so expect slightly different results for outlines.<br>2) The Garmin format doesn't allow a single polygon with more than 255 points, so mkgmap<br>has to split a complex polygon into smaller pieces.<br>3) For lower resolutions, the raster is less precise, means, for 23 points are ~4.6m, 22 -> ~9.6m and<br>so on. <br>4) For lower resolutions, a variant of the Douglas-Peucker-Algo is used to reduce the img size.<br>You can change the effect of this by using the "Optimization options":<br><a href="http://www.mkgmap.org.uk/doc/options" target="_blank">http://www.mkgmap.org.uk/doc/options</a><br> <br>See also<br><a href="http://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm" target="_blank">http://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm</a><br><br>Gerd<br><br><div><hr>Date: Sat, 28 Feb 2015 01:33:18 -0300<br>From: <a href="mailto:alexandre.loss@gmail.com" target="_blank">alexandre.loss@gmail.com</a><br>To: <a href="mailto:mkgmap-dev@lists.mkgmap.org.uk" target="_blank">mkgmap-dev@lists.mkgmap.org.uk</a><br>Subject: [mkgmap-dev] Complex ocean polygon hiding the islands<div><div class="h5"><br><br><div dir="ltr"><div><div>Hi guys,</div><div><br></div><div>Please see if any of you can help me ...</div><div><br></div><div>I have an ocean polygon with multiple edges and in the middle of these there are several islands that are in fact holes in the polygon.</div><div>Here's an example:</div><div><br></div></div><div><img src="cid:ii_14bce6a1dbbedbf6" alt="Imagem inline 1"><br></div><div><br></div><div>Showing only the contour lines, the polygon is drawn as follows:<br></div><div><div><br></div><div><br></div></div><div><img src="cid:ii_14bce6c2101d9500" alt="Imagem inline 2"><br></div><div>Zooming...</div><div><img src="cid:ii_14bce6ce0f0977e6" alt="Imagem inline 3" height="350" width="558"><br></div><div><br></div><div><div>When I compile the map, the islands/holes are overlapped by the sea.</div><div>I noticed that when the polygon is less complex, this overlapping phenomena doesn't happens. Its looks like mkgmap simplifies complex polygons.<br></div><div><br></div><div>Is there any option that I can use in mkgmap to respect the layout of complex ocean polygons?</div></div><div><br></div><div>By the way, if this isn't the right list to ask this kind of question, please let me know cause I'm new here.</div><div><br></div><div>Thanks.</div><div><br></div><div>Alexandre</div></div>
<br></div></div>_______________________________________________
mkgmap-dev mailing list
<a href="mailto:mkgmap-dev@lists.mkgmap.org.uk" target="_blank">mkgmap-dev@lists.mkgmap.org.uk</a>
<a href="http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev" target="_blank">http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev</a></div> </div></div>
<br>_______________________________________________<br>
mkgmap-dev mailing list<br>
<a href="mailto:mkgmap-dev@lists.mkgmap.org.uk">mkgmap-dev@lists.mkgmap.org.uk</a><br>
<a href="http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev" target="_blank">http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev</a><br></blockquote></div><br></div>