<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoNoSpacing, li.MsoNoSpacing, div.MsoNoSpacing
{mso-style-priority:1;
margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNoSpacing>The OSM planet-land is created from the coastline dataset. From time to time it might be reasonable to use the inverse of it, the planet-sea, or even both of them. But, creating the planet-sea is not just a simple exercise. Here is one model/option in bullets how this can be done efficiently.<o:p></o:p></p><p class=MsoNoSpacing>-The first several steps are common. The coastline data is extracted from the planet dump. So this set is processed by a data preparation chain to remove replications, overlaps, corridor overlaps and the like. So, all border polygons are created by linear connections of the processed coastline polylines. Eventual gaps and open polygons are corrected, if possible.<o:p></o:p></p><p class=MsoNoSpacing>-The next phase is the polygons-to-areas transformation. The result is a set of simple areas where any outer/enclosing border polygon contains an arbitrary number of hole/excluding border polygons. Simple areas with no holes are primitive areas. The result is the planet-land and its creation takes about 1h and 40sec on my laptop.<o:p></o:p></p><p class=MsoNoSpacing>-The planet-sea might be created in the same way by adding the universal/unit polygon before the polygons-to areas procedure. The universal polygon/area is the rectangular polygon over the planet-frame (bounding box). While the result, as an inverse of the planet-land, should be quite correct, the procedure could take discouragingly long time. Here is one highly efficient alternative.<o:p></o:p></p><p class=MsoNoSpacing>-From the planet-land extract all primitive areas (polygons with no holes) outside any holes. Add the universal polygon to the rest of the polygons and run the polygons-to-areas structuring. Finally, revers the orientation of the extracted primitive area borders and add them to the holes of the universal polygon, to the largest area from the structuring. This process takes about 45 sec on my laptop. Of course, the resulting planet-land-INVERSED is exactly the same as in the mentioned standard procedure. But, there is though one problem here.<o:p></o:p></p><p class=MsoNoSpacing>-There are 13, and only 13, critical holes in the largest area, in the global ocean, where certain border sections overlap with sections of the outer border of the global ocean. According to the OSM documentation this might be illegal. So, to be quite correct, do the last step.<o:p></o:p></p><p class=MsoNoSpacing>-Remove the overlapping sections from the 13 holes and from the universal polygon. Connect the remaining sections into a polygon and make it oriented as an outer border. Finally, replace the universal rectangle with this large polygon and eventually remove the 13 critical holes.<o:p></o:p></p><p class=MsoNoSpacing>If interested, you may find the planet-land, planet-land-INVERSED and the planet-sea here<o:p></o:p></p><p class=MsoNoSpacing><a href="https://drive.google.com/folderview?id=0B6qGm3k2qWHqflhDVHJoTVBmVmFCZUw3VFlIdUVYS0xTSURJdnlWQUZ5dy1PMVVVcTFLcmc&usp=sharing">https://drive.google.com/folderview?id=0B6qGm3k2qWHqflhDVHJoTVBmVmFCZUw3VFlIdUVYS0xTSURJdnlWQUZ5dy1PMVVVcTFLcmc&usp=sharing</a><o:p></o:p></p><p class=MsoNoSpacing>created from the latest OSM dump. The tiled versions are added for practical reasons. You can download and use them as you like but please respect the OSM licencing roles.<o:p></o:p></p><p class=MsoNoSpacing>Regards, Sandor.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>