The Idaho Geological Survey collects and publishes new geologic mapping data digitally. The survey's Digital Mapping and Information Lab digitizes geologic maps using large format digitizing tablets and Pentium PCs loaded with AutoCAD r12 and CADmappr, a third party geologic mapping utility. The digitizing process is controlled and semi-automated by CADmappr. Digitizing proceeds in a systematic manner starting with the contacts, then the dangling faults, then the geologic symbols, and finally the map units are labeled including label points for GIS export. When complete, a copy of this database version of the map is reduced to publication scale from the Idaho State Plane Coordinates in which it was digitized. Legend items such as the correlation chart, any cross sections, and the unit descriptions are then imported for layout. Once layout is complete the map is plotted for author and mapping lab review. Revisions to the map are made after author, technical, and editor reviews. Changes in the geology are made in the database. Postscript files are generated from the final map and used to produce press-ready negatives on an image setter. Metadata is collected during the map-making process. Geologic map themes digitized in CADmappr/AutoCAD can be exported as Arc/Info E00 files.
The Idaho Geological Survey (IGS) at the University of Idaho serves the state of Idaho through geologic research, and is also charged with collecting and distributing geologic data. The survey's Digital Mapping and Information Lab (DMI) produces all new geologic mapping digitally. Mapping can be released as paper maps and in a Geographic Information System (GIS) format. The purpose of this paper is to show how geologic mapping data at IGS is captured, published, and released for GIS.
IGS publishes two categories of geologic map products: Technical Reports (95%) and Geologic Map Series full-color press-run maps (5%). Technical Report maps include new 1:24,000 scale mapping and compilations of existing geology. Most new mapping is released as black and white maps reproduced xerographically. Future compilations will be published at a scale of 1:100,000 as plot-on-demand color maps. All published geology is available in digital format as GIS (Arc/Info) coverages or Computer Aided Drafting (CAD) drawings.
IGS began using CAD software in 1989 to draft geologic mapping. Generic CADD, a low-end CAD package, was originally used. Experience gained with this software proved that geologic maps could be produced and published digitally. But it also showed that a more robust software was needed to improve publication quality and GIS output.
Map data capture is now done entirely in AutoCAD r12, a popular and powerful CAD software. CADmappr, a third party AutoCAD geologic mapping utility, permits IGS to capture geologic map data, publish, and export to GIS. By taking advantage of AutoCAD's editing and programming features, CADmappr, with its customized additions, permits the followings mapping functions:
The Idaho Geological Survey's mapping lab is primarily PC based. AutoCAD is run in DOS on Pentium machines with 48-64 megs of RAM. Files are served locally to the digitizing stations with a Windows NT server. Digitizing is done on two large format CalComp tablets. The survey has an eight year old Hewlett-Packard DraftMaster pen plotter which is used to plot line work for visual inspection. HP InkJet plotters are available through the campus network and are used for color plots and plot-on-demand publications. Unix based Arc/Info is accessed at one of the university labs or via x-terminal emulation software on one of the lab's PCs. The long-term direction of the lab is to move gradually over to Windows NT-based systems.
The map author is required to submit the following with every new map:
The mapping lab is responsible for digitizing the geology, adding the necessary map components, performing layout tasks, and finally seeing the map through to publication. The lab collects and maintains metadata for each geology data set. The lab also maintains all generated geologic map data.
Geology is either digitized by hand on a high-accuracy digitizing tablet or scanned by high-resolution scanner with subsequent data conversion and extraction. IGS digitizes by tablet most new maps because this process can be accomplished entirely in-house. CADmappr semi-automates the digitizing process through a series of dialog box-driven routines. Digitizing proceeds unit-by-unit. Only one copy of each contacts or fault-contact is digitized. Remaining dangling faults are then added. After that, geologic attitudes (strike and dip, foliation, etc..) and the other geologic symbols are digitized. Finally map unit labels are added including label points (points necessary for topology in a GIS.) Once digitizing is complete, a unit-by-unit visual on-screen check is done. The map is plotted on Mylar for further line work inspection. Lines should look drawn, not digitized. Necessary additions and changes are then made. The digitizing of this database version of the map, takes place in Idaho State Plane Coordinates. Key metadata information is noted for each work session. The IGS map publication process is outlined in Figure 1.
Figure 1. Flowchart showing geologic map production [110 K GIF]
A copy of the database map is reduced to final publication size. Legend building proceeds in this scaled, publication copy. This step prevents the database from being corrupted during layout and allows the cartographer to work in the more familiar units of points and inches. Much of the layout process is accomplished via menu driven utilities. Importing text, laying out unit boxes, and designing correlation charts are all semi-automated procedures. Currently, unit descriptions, references, and other text are edited in WordPerfect and then imported into AutoCAD in columns as ASCII text. Parts of the legend can be imported from a catalog of template drawings compiled over the years.
Each section of the legend is placed in a different CAD layer making the map more editable. Postscript configuration output is based on these layer names. Final publication line widths, line grey scales, and line join types are also assigned by layer. When the legend is complete the map is plotted again on Mylar, temporarily overlaid on a film-positive base map, and Xeroxed for review by the mapping lab and the author.
The author is allowed one chance at this stage of production to make minor content changes to the map. This is followed by a technical review and an IGS editor review. Changes to the geology must be made to the database version of the map. The revised geology is then re-inserted into the publication map. Changes to the legend text are done in either CAD or WordPerfect, depending on the amount of revision. When the changes are completed the map is ready to be configured for publication.
Postscript is a programming language used to make publication-ready output files. CADmappr includes a Postscript output utility which takes advantage of three configuration files: line work, fill colors, and patterns. A default Postscript configuration file for line work is generated by CADmappr and modified in an ASCII editor. Then a Postscript version of the map is plotted on an InkJet device. This map provides a pre-publication test for line widths, fonts and font sizes, and omissions. When ready for press, a full black Postscript file of the map is sent to a contractor with an image setter and a direct negative is made. The final IGS product is a frosted Mylar composite of the image-set geologic map and the screened USGS base map.
Although Technical Reports are currently released in Xeroxed black and white, they can also be done as one-off color plots. A RGB look-up table of geologic unit colors (polygons) is created using, as a guide, the Colors and Patterns Commonly Used in U.S. Geological Survey Publications found in Cartographic and Digital Standard for Geologic Map Information (U.S. Geological Survey, 1995). USGS Digital Line Graph data (DLG) is added and a full-color InkJet version of each Technical Report is plotted.
Digital Raster Graphics (DRG), a scanned base map product, are now available for the entire state of Idaho. IGS hopes to combine these DRG maps with full-color Postscript to publish new Technical Reports as on-demand plotted maps. Currently with new utility software IGS can export the CAD-finished geology as Encapsulated Postscript files (EPS). The EPS files can then be placed in publication layout programs like FreeHand or Adobe Illustrator. These softwares offer improved text and bitmap layout tools and "speak in the language" of publication.
Because of its limited budget, IGS sends few maps to a color press. Except for the base map, color press maps follow most of the production steps discussed above.
IGS is currently working on a map that will go to a color press in the fall of 1997 which serves as an example of how we compile the base map for publication. The base map for this product is constructed from tiled 1:100,000 scale DLGs (transportation, streams, hypsography), a clipped section of the Idaho Public Land Survey System (PLSS) file, and the Idaho Geographic Names Information System (GNIS) file.
DLG data is run through an Arc/Info AML (Arc Macro Language) routine to convert the vector data to AutoCAD Drawing Interchange File (DXF) format and separate it into CAD layers. These DLG tiles are projected, edge-matched, and checked for completeness in AutoCAD. PLSS data is handled much the same way. The GNIS is a listing of place names and their attribute data including a latitude/longitude location. A specially written AutoCAD routine uses a subset of the GNIS and semi-automates the placement, layering, color assignment, font assignment, and rotation of each geographic label.
To add color to the map, a RGB table is created as with Technical Reports. Using this RGB table and the Postscript configuration file, EPS file(s) are created and brought into FreeHand where final text layout is done. When the map is ready for publication, 5 press-ready negatives (cyan, magenta, yellow, black, and a Pantone base map color) are generated from Postscript file(s) on a large format image setter.
All geologic map data digitized in CADmappr can be exported to an Arc/Info E00 file. Many sub-themes can be generated from one CAD geologic database. The usual coverages exported include rocks (lines and polygons of the geology), faults, dikes, fold axis, and three categories of symbols (point data).
A menu-driven series of AMLs facilitates the processing of the geologic data in Arc. Imported data is checked for dangle errors, tables are joined, extra label points are eliminated, and coverages are built.
Data sets also include an ArcView project file which displays all themes and links other relevant databases, including metadata, to the geology.
Data sets are officially released when the map is complete, all metadata is entered, and the data is listed in the IGS List of Publications. Data is delivered on CD ROM.
IGS collects metadata (i.e., data about the data,) on new geospatial products using the Content Standards for Digital Geospatial Metadata (Federal Geographic Data Committee, 1994) as a guide. Each contact, fault, dike, and symbol receives a metadata id tag. This identifier relates the source of the geology to each of its map entities. For example, in a geologic map compilation there may be several sources of geologic data. All the spatial geologic data related to one source will receive the same tag. This tag exports to a "reference _id" field within Arc/Info and can easily be linked to the relevant metadata for that source: scale, digitizing techniques used, author, title, etc.. Geologic map unit descriptions are also included as a database. With the help of geologists, descriptions are summarized and sorted into key fields and linked to the spatial data via the polygon label point.
Currently all metadata is collected in dBASE files to make linking and sorting possible. Metadata "source" fields double as an inventory of IGS digital geologic maps thus serving an in-house data tracking function.
Geologic mapping metadata for several data sets has already been submitted to the Idaho GIS Metadata Server.
Why does IGS use CAD and not GIS software?
The answer is part history and part practicality. IGS uses both types of software and is using more of ArcView to test completed coverages and display linked metadata. But the bulk of the work day is spent in AutoCAD. Digitizing, editing, and layout are all more efficiently done in CAD when compared to many GIS packages. CAD also runs very fast on less expensive PC machines.
What are some of the drawbacks to the IGS approach to digital map capture and publication?
By necessity many routines have been written to digitize, edit, publish, and export to GIS. Many different softwares must be learned to make it all work. This makes the system both flexible and cumbersome. The learning curve for training is long. CADmappr has no documentation outside of what the IGS mapping lab has developed internally.
How long does it take to train someone at IGS to use this system?
This depends on the background and interests of the trainee. On average it take 3 weeks to train someone to digitize well, and another 3 months of supervision before they are ready to complete an entire map for publication.
How long does a geologic map take to digitize and layout for publication?
For a skilled digital cartographer a complex 7.5 minute (1:24,000 scale) map of 300-400 polygons takes 4-6 days to digitize and another day to build the complete legend.