Leming, T.D., May, L.N., Jones, P. 1999. A Geographic Information System for Near Reat-Time use of Remote Sensing in Fisheries Management in the Gulf of Mexico. 85 p. February 11, 1999. http://coastwatch.noaa.gov/pubs/digdocs/nrtgis_final_report2.pdf "A continental land mask was created from the global, self-consistent, hierarchical, high-resolution shoreline database (GSHHS) compiled by Wessel and Smith (1996). The GSHHS is public domain digital coastline file available from the School of Ocean and Earth Science Technology at the University of Hawaii12 and the NOAA National Geophysical Data Center 13 (NGDC) and contains coastlines and closed waterbodies extracted from two widely used public domain databases, the World Data Bank II coastline (WDB) and the World Vector Shoreline (WVS). Lohrenz (1988) indicated that the working scale of the WVS data is about about 1:250,000 and is referenced to the World Geodetic System of 1972 (WGS-72) horizontal datum and the mean high water (MHW) vertical datum." Lohrenz, M.C. 1988. Design and implementation of the digital world vector shoreline data format. Report 194, Naval Ocean Research and Development Activity, Stennis Space Center, Miss., 34 pp. ####################################################################### http://wegener.mechanik.tu-darmstadt.de/GMT-Help/Archiv/1960.html Coastlines, etc * This message: [ Message body ] [ More options ] * Related messages: [ Next message ] [ Previous message ] From: Paul Wessel Date: 1999-04-14 08:11:02 Hi GMT users- Each year I get a few questions like these: 1. "I am making a plot of a small area, using pscoast -Df, and the island that I used to visit as a kid does not show up (or lake, or river, etc)" 2. "When I compared the coastline from pscoast with GPS measurements, the coastline seems shifted by a few hundred meters" 3. "Where this river is wide it is missing entirely, with the result that some of the islands in the river show up as lakes" To simplify the answer, I will assume you have read Appendix K in the GMT Reference & Cookbook section on how the GSHHS coastlines were put together. Answers: There are many possibilities: a) The feature was missing in the original WVS (land outlines) or WDBII (lakes, rivers, boundaries) data set. b) The feature was eaten by our preprocessing steps. c) WVS and WDBII were sometimes incompatible. d) Different datums were used One must remember that the WVS coastline is much higher accuracy than the WDBII lakes and rivers. It has happened that a feature that was considered a coastal lake in WVS (i.e., it did not break the shoreline and thus was not included in WVS) was a bay in WDBII (and thus not included as a lake). The result is that the lake never appeared in GSHHS. Likewise, rivers do not always end at the coastline; it may cross it or not quite make it to the ocean. How can we improve the data? Ideally, we would prefer that some agency announces a sucessor to WVS and WDBII that is better, and we can start from that point. We do not want to be the curators of these data. In the mean time: 1. If you can show us that a missing feature is indeed in the original WVS or WDBII data then _maybe_ I can find time to check the processing code. I need much motivation to dig into all that stuff again. 2. If you have a high-resolution (i.e., comparable to other features in -Df) digital version of the missing feature, please email it to us with an explanatory note. We may then incorporate it in the next version. 3. The rivers seem to be messed up, either in the source or by us. If you have digitized missing pieces please share them with us. 4. The shift that some have documented may be related to datum. If anybody knows what reference ellipsoid was used for WVS and WDBII we would like to hear it. We made no correction to the lon/lat when making the data compilation. 5. We still miss some recent political borders. It may be premature to add lines in the Balkans, but if you have high-quality political borders not in GMT, please share with us. Paul Wessel, Professor Dept. of Geology & Geophysics School of Ocean & Earth Science & Technology University of Hawaii at Manoa 1680 East-West Road, Honolulu, HI 96822 (808) 956-4778/5154 (voice/fax)