1.What is The Digital Chart of the World?

2.How we changed the data set

3.Arc/INFO users

5.ArcView users

6.Known errors and fixes

7.Contact us

What is the Digital Chart of the World?

      The Digital Chart of the World (DCW) is an Environmental Systems Research Institute, Inc. (ESRI) product originally developed for the US Defense Mapping Agency (DMA) using DMA data. We used the DCW 1993 version at 1:1,000,000 scale. The DMA data sources are aeronautical charts, which emphasize landmarks important from flying altitudes. This explains why there is a separate aeronautical theme with all conceivable airports, yet why on some themes small islands and lakes are simply unnamed points. ESRI, in compiling the DCW, also eliminated some detail and made some assumptions for handling tiny polygons and edgematching. Also, note that the completeness of the thematic categories present in each layer will vary. Please read the layer descriptions (through links in the following table).

How we changed the data set

      The original format of the DCW from ESRI has 2094 separate Arc/INFO workspaces. Each workspace is bounded by latitude and longitude, 5-by-5 degrees. Each can contain up to 25 different thematic layers (see list below). We compiled the original workspaces into countries, territories and states; our server contains about 340 of these areas, from the original 2094 workspaces. We aggregated parts of the tiles one country at a time, and used each country-boundary coverage as a "cookie cutter" to select the thematic data according to country boundaries. Thus our server contains about 5000 thematic layers. Because the process was automated using Arc Macro Language (AML), we have not yet inspected each of the potential 25 themes for each of the 340 areas, so notify us if you find an error.

      The main goal of the project is to deliver data in Arc/INFO format, which is readable by ArcView as well. We also developed a mapping module that (through PERL and AML scripts that call ArcPlot, produces an EPS file, then is converted to a GIF image) produces a view-only but downloadable image. The map is a preview tool; for a final cartographic product, we intend for you to download the data and produce your own map.

Work on the project began in July 1996 and was substantially completed in March 1997.

For Arc/INFO users

Every line coverage needs to be cleaned and every point coverage needs to be built. For line coverages use the Arc command CLEAN, and for point coverages use the Arc command BUILD.

ArcView users

According to the ArcView online help, coverages with more than 5000 arcs can not be imported into ArcView2 (Windows 3.x) using its import program. The following export (.e00) files contain more than 5000 arcs, thus ArcView2 cannot import them as a theme. Therefore, Arc/INFO's IMPORT function must be used to create the coverage. You can then open the new coverage as a theme in ArcView.

It may be possible to use the ArcView3 import function for NT or UNIX machines.

Known errors and fixes

      The original DCW data we used had a few errors. The following sections describe some of the changes we made.

The PONET layer for the following areas may have lost some items in the .pat file, and may not include an .aat file at all. This is because of an error using the Arc/INFO DISSOLVE command. The ponet layers is a network coverage, thus is has an .aat and a .pat info file. While compiling these areas the dissolve command may have deleted the .aat and deleted all the items in the .pat except the dissolve item. This was corrected for all the over data accessed through this web site.

Miscode Errors

The original ESRI tile PG31, item popycoun is miscoded, thus some national boundaries were wrong. The affected areas were: Uganda, Central African Republic, Zaire, and the Sudan. Our data was fixed on 1/23/97.

The original ESRI tiles XH32, XH31, XG33, XG23, and YG12 PONET coverages popycoun item was recoded on 1/13/97. The affected areas were: Federated States of Micronesia, Guam, and the Northern Mariana Islands.

The original ESRI tile GK21 was recoded on 1/17/97. Michigan was added to popyadmin for one polygon.

Compile Errors

Other errors in the original DCW tiles were found when our AML script tried to compile the layers in the following list. 0ur data was corrected using the Arc command CLEAN, in 1/97:

Edgematching and Line Connectivity/Polygon Closure

Edgematching of production modules (the nonoverlap areas of the ONCs and JNCs) was accomplished manually. The basic objective was to establish a cartographically pleasing match across ONC boundaries whenever possible. The most accurate and/or current modules were given priority. In poorly mapped areas of the world, severe feature offsets do occur. In these extreme cases of feature offset, no edgematching was attempted because the degree of the offset made the differences irreconcilable. Significant feature offsets also occur in the instances where the source materials used to compile the ONCs could not be reconciled. These type of situations may be located anywhere in a tile.

Some Digital Chart of the World layers are developed from ONC separates that do not contain the necessary connectivity or closure for the linear and polygonal features represented. For example, road segments are broken on the separates for the text and urbanized area polygons. These breaks in connectivity were usually resolved at the map preparation stage.

Layer Descriptions

Political and Oceans layer

Coverage name: PONET
Feature class type: Polygon
Items, codes, and values

POPYTYPE
Political/Oceans polygon type

Code Definition

1. = Land
2. = Open Ocean
3. = Polar ice (on water)*
4. = Pack ice (on water)*
5. = Shelf ice*

* Ice on land is contained in the DNNET coverage. These phenomena occur only on Antarctica, where extensive portions of the land/ocean shoreline is covered by ice.

Coverage name: PONET
Feature class type: Line
Items, codes, and values

POLNTYPE
Political/Oceans line type

Code Definition

1. = International boundary, de jure
2. = International boundary, de facto
3. = International boundary, de jure and de facto
4. = Subnational administrative boundary, first order
5. = Subnational administrative boundary, second order
6. = Treaty or occupational line (demilitarized zones)
7. = Coastal closure line (used to connect ocean shoreline across river mouths, glaciers, lagoons, fjords, and so forth)
8. = Ocean demarcation line (used to separate ocean aggregations)
9. = Ice line (used to separate types of sea ice)
10. = Coastline
11. = Ocean/Sea ice boundary
12. = Seawall
13. = International date line

88. = Arbitrary connector (if needed)

99. = None (used for tile border)

POLNSTAT
Political ocean line status

Code Definition

1. = Definite (boundary or coastline)
2. = Approximate (boundary) or fluctuating (coastline)
3. = Indefinite (boundary or unsurveyed (coastline)
4. = Man-made (coastline) (dike)
5. = Indeterminable (coastline)
6. = Ice cliff (when coincident with the coastline or ice line)
7. = Political boundary (that is, based on single-line river or stream location)
8. = Connector (international or administrative boundary extensions through inland water areas)
9. = 5- degree by 5-degree tile boundary

88. = ONC module boundary section retained to provide "edgematch" connection across ONC sheets

Populated Place layer

Coverage name: PPPOLY
Feature class type: Polygon
Items, codes, and values

PPPYTYPE
Populated place polygon type. This coverage contains depictions of the urbanized areas (built-up areas) of the world that can be represented as polygons at 1:1,000,000 scale. The built-up areas represent the shape of an urbanized area as viewed by the air observer. These outlines do not necessarily conform to political boundaries.

Code Definition

1. = Urbanized area
2. = Kampong (small villages or groups of houses, especially in Southeast Asia)

9. = None (non-urbanized area within urbanized area)

Coverage name: PPPOINT
Feature class type: Point
Items, codes, and values

PPPTTYPE
Populated place point type.

Code Definition

1. = Populated place (no subcategories*)
2. = Populated place (associated with place names within urbanized areas)
3. = Village, strategic, or landmark place associated with a special symbol identified with an ONC marginal note
4. = Kampong (small villages or groups of houses, especially in Southeast Asia)
5. = Circular Village

* On ONCs there are different symbols and text sizes for differentiating the size or relative importance of populated places. The rank value associated with these symbols varies from sheet to sheet; for that reason, no attempt was made to code for the different populated place symbols in the database.

PPPTNAME
Place name. The item PPPTNAME contains a thirty-character field to carry the specific name of the populated feature as it appears on the ONC. Names are contained in this item.

Railroad layer

Coverage name: RRLINE
Feature class type: Line
Items, codes, and values

RRLNTYPE
Railroad line type.