coastline_gen simple coastline generalization

Here you can find an implementation of a simple raster based technique to generalize coastlines and other polygon features for map rendering. You can find some background information on the purpose of this in my essay on coastline generalization. The newest version of this tool is available on github.

The program is written in C++ and uses the CImg image processing library and should work on all platforms supported by it.

The source package includes a makefile for building. It also contains a test target that demonstrates use of the tool by generalizing the coastline of Greece and the Aegean sea (see image on the right, move mouse over to see a generalized version) from the sample data set linked below. If you want to see how a generalized coastline looks like in a practical example you can do so in the demonstration map.

Version 0.5 includes new functions for generalizing inland waterbodies. The new functions are not yet properly documented and the demo in the makefile has not been updated either.

This program is licensed under the GNU General Public License version 3.

• Documentation (also included in the package)
• coastline_gen-0.5.zip (22kB) version 0.5 source package.
• greece.sqlite (7MB) Sample data from OpenStreetMap processed using OSMCoastline. This data is Copyright OpenStreetMap contributors and licensed under ODBL. You do not need to download this separately, make test will do that using wget.

Visitor comments:

by kusmi from Switzerland posted on Wed Feb 13 2013 16:27:29

reply

Looks very nice and is the first generalization algorithm I found on the internet :-)

BTW, instead of only generalizing the coast-line, why not merging (union) the natural=water, riverbanks and coastlines so the Suez-Canal, Amazon also renders correctly?

Using your bitmap approach, the union operation would be very efficient (just add together the pixel-data of the corresponding vector sources) - I'm using a similar approach for fast union and reducing data to fixed-point coordinates.

by chris from Germany posted on Wed Feb 13 2013 17:52:48

reply

Hi kusmi,

the technique is not really suited for generalizing rivers since on a small scale map rivers are usually rendered as a single line and not as an area.

Lakes can be generalized using the same technique but need to be specifically separated from the ocean - that is what the '-f' option is for.

Leave a comment

You have to enable Javascript to be able to write comments.

Please enter the code you can see in the image on the left to verify you are a human and not a spamming script.

*	* Required field

Information about you

Your name/nickname:	*
Your country:	Afghanistan Albania Algeria American Samoa Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Ascension Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo, Republic of Cook Islands Costa Rica Croatia Cuba Cyprus Czech Republic Democratic Republic of the Congo Denmark Djibouti Dominica Dominican Republic East Timor Timor-Leste Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Great Britain Greece Greenland Grenada Guadeloupe Guam Guatemala Guernsey Guinea-Bissau Guinea Guyana Haiti Heard and Mc Donald Islands Honduras Hong Kong Hungary Iceland India Indonesia Iran Iraq Ireland Isle of Man Israel Italy Ivory Coast Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Kuwait Kyrgyzstan Lao Latvia Lebanon Lesotho Liberia Libya Liechtenstein Lithuania Luxembourg Macao Macedonia Madagascar Malawi Malaysia Maldives Mali Malta Marshall Islands Martinique Mauritania Mauritius Mayotte Mexico Micronesia Moldova Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar/Burma Namibia Nauru Nepal Netherlands Antilles Netherlands New Caledonia New Zealand Nicaragua Nigeria Niger Niue Norfolk Island Northern Mariana Islands North Korea Norway Oman Pakistan Palau Palestinian National Authority Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Island Poland Portugal Puerto Rico Qatar Reunion Island Romania Russia Rwanda Saint Helena Saint Kitts and Nevis Saint Lucia Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Príncipe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and South Sandwich Islands South Korea Spain Sri Lanka St. Pierre and Miquelon Sudan Suriname Svalbard and Jan Mayen Islands Swaziland Sweden Switzerland Syria Taiwan Tajikistan Tanzania Thailand Tibet Timor-Leste (East Timor) Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay U.S. Minor Outlying Islands Uzbekistan Vanuatu Vatican City State Venezuela Vietnam Virgin Islands (British) Virgin Islands (U.S.) Wallis and Futuna Islands Western Sahara Yemen Zaire Zambia Zimbabwe
Your e-mail address:	will not be made public
Link to your website:	will be displayed with your posting

Your comment (no HTML)

* If you want to send a private message to the author of this website you can do so via Email. The comments will be reviewed before they are added to the site. So you might need to wait some time until your entry turns up. Please note this comment function is intended for commenting on the text and images, not for discussing political or religious views. Comments with no relation to the content of this site will not be approved.

By submitting your comment you agree to the privacy policy and agree to the information you provide (except for the email address) to be published on this website.