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Coastline Extractor

Caution: These data are outdated. Please download desktop software under "Related Links" below to extract updated data from GSHHG.

Geographic Range of Coastline to Extract
(decimal degrees, west and south are negative)

upper latitude
westernmost longitude
easternmost longitude
lower latitude

Note: Please enter the geographic range first, then choose criteria below.

If you select a range that covers more than a few degrees,
be prepared to wait while the data are extracted and (optionally) the coastline image is created.


Coastline database:

Compression method for extracted ASCII data:
None GNU GZIP UNIX Compressed ZIP

Coast Format options:
GMT ASCII Arc/Info Ungenerate Matlab Splus Mapgen

Coast Preview options:
No preview GMT Plot

Extract the Coast:

Note: If you preview the coast, please wait for it to be generated! If you abort and reload the form, you will just create another process that will slow things down even more!


The Coastline Extractor was created by Rich Signell of the U.S. Geological Survey / Geologic Division / Coastal and Marine Program / Woods Hole Field Center. The extractor pages are currently hosted by the NOAA/National Geophysical Data Center, Marine Geology and Geophysics Division.

Caution: These data are outdated. Download desktop software under "Related Links" below to extract updated data.


The electronic form above allows you to extract coastline segments bounded by a specified latitude/longitude range. Also produces a "page size" screen plot of the coast you extracted in a cylindrical-equidistant projection.

The selected data returned by the query is an ASCII flat file with two columns containing longitude and latitude in decimal degrees (west negative). The default GMT ASCII format is lon, lat with new segments separated by a line containing the character ">". The MAPGEN format is lon, lat with new segments separated by a line with characters "# -b". The MATLAB format is the same, but with the characters "nan nan" indicating line breaks, so in MATLAB you can type "load coast.dat" then "plot(coast(:,1),coast(:,2)". The Arc Ungenerate format works with ArcGIS®.

ArcView will not read the Ungenerate format directly, but you can convert from Ungenerate to a Shape file that ArcView can read using the script gen2shap1.ave. For MAPINFO users, there is a tool CoastCon.zip from Peter Lyngs that converts the MAPGEN format output to MapInfo Import Files (MIF).

The ASCII files may be compressed in a variety of formats before downloading.

The default values below will give you the WVS coastline for Cape Cod, Marthas Vineyard and Nantucket in Massachusetts, USA.

About the data sets:
  • World Coastlines and Lakes. Crude. World Wide Coverage. This data is suitable for map scales of 5,000,000 or smaller.

  • World Data Bank II. Fair Resolution. World Wide Coverage. This data is suitable for map scales of 2,000,000 or smaller. Also contains international and internal political boundaries and rivers.

  • World Vector Shoreline. Better Resolution. World Wide Coverage. This data is suitable for map scales of 1:250,000 or smaller.

  • NOAA/NOS Medium Resolution Digital Vector Shoreline. Best Resolution. United States Coverage, digitized from NOAA nautical charts. This data is suitable for map scales of 1:70,000 or smaller. Note: There may be a few odd data points in this version of the data set (September, 1994).

Our processing details may be found here.

Note: If you are interested in making the coastline continuous and you have Matlab, click here.


Related Links