Sea Coastline


This section is closely related to the previous one, which was about a DEM, because the coastline of the world can be used to correct the pixel values of the DEM. Therefore, there is discussed the problem of obtaining sufficiently accurate lines in vector form in all coastal areas of the Earth. The accuracy of its provisions should be comparable, but no worse than the size of one pixel of the DEM. For a DEM with a resolution of 1 arc second, the release of which is expected in 2015, this is about 30 meters.

The original data sources

From any open resources can take the raw data?

Here are some of them.
1. Vector coastline obtained from DEM (previous section).
2. Vector map of USA VMap0, scale 1:1M, available for download with data on the whole world, including coastline.
3. Vector map of USA VMap1, scale of 1:250K, available for download for approximately 1/3 of the Land area.
Sources 2 and 3 will pass on the accuracy of the data. The accuracy of maps of natural scale 1:250K has a value of about 100 meters, which is 3 times worse than required. Accuracy would be vector maps of scale 1:50K and larger.
4. Vector map OSM (OpenStreetMap project), with almost the entire world. Unfortunately, OSM data can vary significantly according to the accuracy of representations depending on the region of the Earth.
5. Images GoogleEarth on all territory of the Earth, represented in raster form. Tools program GoogleEarth sufficient for the organization of test vector data and for their correction. Here is disadvantage - large volume of work.

Surely there are other open sources that you can use. I hope to complete this list, including with the help of readers and users of my data.

Examples of the coastline in a variety of areas

Download examples in KML format here:

Review examples

1. The coastline of the continents and Islands (even if they are closed) are presented in the KML file lines (LineString). Also in the KML files, there are Polygons, which may have an external contour and internal contours. Polygons digitized lake, located close to the coastline, but not having access to the sea. The height of the water level of the lakes is indicated by the value of the third coordinate (usually the height is 0).
2. Pictures displayed GoogleEarth, composed of a plurality of stacked slices. There are cases when the alignment error is 30 meters or more (especially for North island districts). Therefore, one can observe the situation when a part of the coastline fits well on GoogleEarth images, and some is offset by the same amount.
3. In the territory above 70 degrees North latitude there is no good vector data or good photo quality. In these areas, the coastline is not made.

Coastline ambiguities

1. Where is the dividing line between the sea and into the sea the river?
In this case the issue is solved as follows. Until such time as the absolute height of the water level in the river is not different from sea level (i.e. equal to 0), it is assumed to be sea. Where the river water level rises at a significant magnitude, there is a line of division of the river and the sea. A significant value is considered to be 1 meter. To determine the place of raising the level of river water by significant magnitude, and hence the line section of the river and sea, DEM is used.
Note that in many flat and low-lying coastal areas of the Earth you can watch "the deep penetration" of the sea into the continent along wide rivers.
2. Small Islands, rocks sticking out of the water, etc., have coastline or not?
Yes, if the largest linear size of them more than 30 meters.
3. Lagoons, ephemeral ponds, flooded by tidal areas, etc. - this land or sea?
This is a complex issue which is solved by operator-interpreter, based on his experience in the recognition of satellite images GoogleEarth.
4. Dams (jetties, wharfs) and bridges - this land or sea?
If the width of the dam more than 30 meters, then it is land. Bridges are not land and therefore not shown.

Dissemination of data

Send me requests.
Created data may be communicated to interested parties for noncommercial use in case of fulfilment of two conditions:
1. The availability of data on the required territory (the project is not completed, some of the data are still in production).
2. The user gives the obligation to verify the quality of data and to send me information about bugs.

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