Mapping Toolbox

dcwdata

Read selected data from the Digital Chart of the World

Syntax

• struct1 = dcwdata(library,latlim,lonlim,theme,topolevel)
  struct1 = dcwdata(devicename,library,...)
  [struct1,struct2,...] = dcwdata(...,{topolevel1,topolevel2,...})
  

Background

The Digital Chart of the World (DCW) is a detailed and comprehensive source of publicly available global vector data. It was digitized from the Operational Navigation Charts (scale 1:1,000,000) and Jet Navigation Charts (1:2,000,000), compiled by the U.S. Defense Mapping Agency (DMA) along with mapping agencies in Australia, Canada, and the United Kingdom. The digitized data was published on four CD-ROMS by the DMA and is distributed by the U.S. Geological Survey (USGS).

The DCW is out of print and has been succeeded by the Vector Map Level 0 (VMAP0).

The DCW organizes data into 17 different themes, such as political/oceans (PO), drainage (DN), roads (RD), or populated places (PP). The data is further tiled into 5 by 5 degree tiles and separated by topology level (patches, lines, points and text).

Description

struct = dcwdata(library,latlim,lonlim,theme,topolevel) reads data for the specified theme and topology level directly from the DCW CD-ROM. There are four CDs, one for each of the libraries: 'NOAMER' (North America), 'SASAUS' (Southern Asia and Australia), 'EURNASIA' (Europe and Northern Asia), and 'SOAMAFR' (South America and Africa). The desired theme is specified by a two-letter code string. A list of valid codes is displayed when an invalid code, such as '?', is entered. The region of interest can be given as a point latitude and longitude or as a region with two-element vectors of latitude and longitude limits. The units of latitude and longitude are degrees. The data covering the requested region is returned, but will include data extending to the edges of the 5-by-5 degree tiles. The result is returned as a Mapping Toolbox geographic data structure.

struct = dcwdata(devicename,library,...) specifies the logical device name of the CD-ROM for computers that do not automatically name the mounted disk.

[struct1, struct2,...] = dcwdata(...,{topolevel1,topolevel2,...}) reads several topology levels. The levels must be specified as a cell array with the entries 'patch', 'line', 'point' or 'text'. Entering {'all'} for the topology level argument is equivalent to {'patch', 'line', 'point', 'text'}. Upon output, the data structures are returned in the output arguments by topology level in the same order as they were requested.

Remarks

Latitudes and longitudes use WGS84 as a horizontal datum. Elevations are in feet above mean sea level. The dataset does not contain bathymetric data.

Some DCW themes do not contain all topology levels. In those cases, empty matrices are returned.

The data is tagged with strings describing the objects. Some data is provided with alternate tags in tag2 and tag3 fields. These alternate tags contain information that supplements the standard tag, such as the names of political entities or values of elevation. The tag2 field generally has the actual values or codes associated with the data. If the information in the tag2 field expands to more verbose descriptions, these are provided in the tag3 field.

Point data for which there are descriptions of both the type and the individual names of objects is returned twice within the structure. The first set is a collection of points of the same type with appropriate tag. The second is as a set of individual points with the tag 'Individual Points' and the name of the object in the tag2 field.

Patches are broken at the tile boundaries. Setting the EdgeColor to 'none' and plotting the lines will give the map a normal appearance.

The DCW was published in 1992 based on data compiled some years earlier. The political boundaries do not reflect recent changes such as the dissolution of the Soviet Union, Czechoslovakia, and Yugoslavia. In some cases, the boundaries of the successor nations are present as lower level political units. A new version, called VMAP0.

Examples

On the Macintosh:

• s = dcwdata('NOAMER',41,-69,'?','patch');
  ??? Error using ==> dcwdata
  Theme not present in library NOAMER
  Valid two-letter theme identifiers are: 
  PO: Political/Oceans        
  PP: Populated Places        
  LC: Land Cover              
  VG: Vegetation              
  RD: Roads                   
  RR: Railroads               
  UT: Utilities               
  AE: Aeronautical            
  DQ: Data Quality            
  DN: Drainage                
  DS: Supplemental Drainage   
  HY: Hypsography             
  HS: Supplemental Hypsography
  CL: Cultural Landmarks      
  OF: Ocean Features          
  PH: Physiography            
  TS: Transportation Structure
  POpatch = dcwdata('NOAMER',[41 44],[-72 -69],'PO','patch')
  POpatch = 
  1x234 struct array with fields:
      type
      otherproperty
      tag
      altitude
      lat
      long
      tag2
      tag3
  

On a MS-DOS based operating system with the CD-ROM as the 'd:' drive:

• [RDtext,RDline] = dcwdata('d:','SASAUS',[-48 -34],[164 180],...
       'RD',{'text','line'});
  

On a UNIX operating system with the CD-ROM mounted as '\cdrom':

• [POpatch,POline,POpoint,POtext] = dcwdata('\cdrom',...
       'EURNASIA',-48 ,164,'PO',{'all'});
  

See Also

vmap0data	Read selected data from the Vector Map Level 0
dcwgaz	Search for entries in the Digital Chart of the World gazette
dcwread	Read a Digital Chart of the World file
dcwrhead	Read a Digital Chart of the World file header
displaym	Project data contained in a map structure
extractm	Extract vector data from a map structure
mlayers	GUI for manipulating map layers

References

The format and the history of the DCW are described in references [1], [2], and [3] located in the Bibliography at the end of this chapter.

avhrrlambert

dcwgaz