OGF:Making an island inside of tidalflat

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Sometimes islands are fully surrounded by tidal land. To draw such islands, you better use relations for a clear mapping. This is no wizard-work, if you go step for step.

1st Step

Draw a line for the outer boundary of the tidal land area. You give no tag for this line, because the information (that it will be tidalflat) will be "carry" from the relation. Then create a new relation with this tags for the relation:

  • type = multipolygone
  • natural = wetland
  • wetland = tidalflat
  • name = Name (may be "XYZ Sand" or "XYZ Bank"). To given names make it more easy to hold the overlook about the different relations.

Define for your first line the role "outer" in your first relation.

This outer area is cut of from the sea and will be mapped as tidal land - here you need no coastline-tag.

2nd Step

Draw inside your first line a second line for the area of the island in the usual anticlockwise direction. Tag this line as natural = coastline. This line please set in your first relation with the role "inner".

If your island will have on the whole area only one natural or landuse characteristic, then you can skip the step 3 and 4 and you can fill the area of the island with the wished natural- or landuse-tag.

3rd Step

Create for the second line (the coastline-line) a new relation for your island. Please use the tags

  • type = multipolygone
  • natural = wetland
  • wetland = marsh
  • name = Name of the island

This second line will have in the second relation the role "outer" - so this second line, the "coastline-line" is inner in the first relation and outer in the second relation.

Instead of natural=wetland and wetland = marsh sure you can use an other tag, if your island will have an other characteristic.

If you want, you can draw not only one, but two or more islands in your tidal land area. If you want this, please repeat steps 2 and 3. For each more island you need one more relation. At this point you will be happy, if you have given names for your island-relations.

4th Step

Til now your island (or your islands) is an area of only marshland. If you will change this, draw a third line inside the second line for this areas, what will be no marshland. This lines in the second relation (the relation of the island) must be defined with the role as "inner". In this "inner" area then you can draw your other natural or landuse tags as lines or areas as usual (may be some bushland, meadow, farmland or streets and houses). Sure you can create more as one of such "inner" areas.

5th Step

If you look to your area after saving, the island will be "blue". No sorrow - please wait til the coastline is updated later and your island will be mapped as land inside the tidalflat.

An example of such islands you can see here [1]