Digital Cartography 

By Michael A. Domaratz and Jo Anne Stapleton 

PETROLEUM POTENTIAL OF WILDERNESS LANDS IN THE 

WESTERN UNITED STATES 

G E 0 L 0 G I C A L S U R. V E Y C I R C U LA R 9 0 2 - 8 

CONTENTS 

Page 

Abstract---------------------------------------------------------------------- B1 

Introduction------------------------------------------------------------------- 1 

Dataencoding----------------------------------------------------------------- 1 

Themes digitized--------------------------------------------------------------- 2 

Wilderness Lands ----------------------------------------------------------- 2 

USGS petroleum provinces---------------------------------------------------- 2 

Geologic regions ------------------------------------------------------------ 2 

Intermediate products----------------------------------------------------------- 2 

~aps --------------------------------------------------------------------- 2 

Tabularreports------------------------------------------------------------- 3 

Qualitative petroleum assessment reporting ---------------------------------------- 3 

Digital activities ------------------------------------------------------------ 3 

Published map series · -------------------------------------------------------- 4 

Summary--------------------------------------------------------------------- 4· 

Referencescited---------------------------------------------------------------- 4 

III 
PETROLEUM POTENTIAL OF WILDERNESS LANDS IN THE WESTERN UNITED STATES 

Digital Cartography 

By Micha.el A. Domaratz and Jo Anne Stapleton 

ABSTRACT 

The petroleum resource assessment program for the Wilderness Lands in the Western United States involved the analysis 

of a large volume of spatial data. A method was needed to 

expedite the gathering, managing, and manipulating of this 

spatial data in a precise and versatile manner and to provide 

results quickly. Digital techniques were used to process large 

volumes of data, such as boundaries of Wilderness Lands, 

USGS petroleum provinces, geologic and tectonic boundaries, 

and locations of wells drilled within or near Wilderness Lands. 

These techniques were used to provide area calculations, tabulations of types of Wilderness Lands and identification of controlling agencies. Digital techniques were also successful as a 

means of generating statistical reports and graphic products 

rapidly. 

Computer-generated maps were plotted showing the 

geologists' qualitative petroleum potentials for each of the Wilderness Lands. A series of printed maps for each State accompanies this circular showing the location and qualitative petroleum potential of the Wilderness Lands studied, the USGS petroleum provinces and other base information about the State 

(Miscellaneous Investigations Series Maps 1-1537 through 1-

1547, in press). 

INTRODUCTION 

The petroleum resource assessment program for 

the Wilderness Lands in the Western United 

States involved the analysis of a large volume of 

spatial data. A method was needed to gather, to 

manage, and to manipulate this spatial data in a 

consistent manner. This method had to be able to 

generate various map products, report the interrelationships between different themes of data, 

and generate other statistical reports (such as 

area calculations). This method had to be precise 

and versatile and had to provide results quickly. 

After discussing their requirements with members of the National Mapping Division and seeing 

the techniques used in digital (computer) applications in cartography, the geologists agreed that 

digital techniques would meet their needs. These 

techniques offered several advantages over manual methods of performing the required analyses. 

Digital techniques can be used to process large 

volumes of data efficiently and in a consistent 

manner and to generate a great variety of graphic 

products quickly and precisely. They can be used 

to generate statistical reports such as area calculations, to compare the occurrences of themes in a 

given area, and to cross-tabulate the different 

combinations of themes that exist. Finally, the 

data produced with these methods can be used 

with other systems and data files for additional 

analysis. After further consultations, the National 

Mapping Division agreed to supply digital cartographic support for the project. 

B1 

DATA ENCODING 

These digital cartographic techniques require 

tpat the data to be analyzed exist in digital (computer-compatible) form. All of the data sources 

available for the themes required, however, 

existed as maps. The first step to be performed, 

therefore, was the digital encoding, or digitizing, 

of the map data for these themes. 

The purpose of the digitizing process is to digitally encode the information for a theme shown on 

a map. This information includes such concepts as 

the location of points, lines, and areas; the connectivity between different lines; and the adjacency 

of different areas. To encode these concepts into 

the computer, a special data organization, a topological data structure, is employed. The topological data structure permits simple applications such as drawing all of the lines found on a 

map, as well as more advanced applications su~h 

as assigning colors to different shapes and calculating the areas of shapes. This data structure 

was used in digitizing the themes required for the 

petroleum resource assessment program. 

Most of the digitizing was done by using stablebase film materials. All of the digitizing was done 

at 1:1,000,000 scale, on a State basis, by using 

manual line-following techniques. 
THEMES DIGITIZED 

The geologists identified three themes of data 

required for the study: the Wilderness Lands 

themselves, the USGS petroleum province units 

(Dolton and others, 1981), and the predominate 

geologic regions of the study areas. 

WILDERNESS LANDS 

Since the Wilderness Lands were the primary 

focus of the study, accurate and recent compilation of these tracts was required. The data were 

digitized from the Bureau of Land Management 

(BLM) Wilderness Status Maps 1981 series 

(1981a-j) for the States of Arizona, California, 

Colorado, Idaho, Montana, Nevada, New Mexico, 

Oregon, Utah, and Wyoming, and the American 

Petroleum Institute map of Wilderness Lands 

(1981) for the State of Washington. Lands adnilnistered by BLM, the U.S. Forest Service 

(USFS), the National Park Serv!ce (NPS), and 

the Fish and Wildlife Service (FWS) were digitized. 

The categories of Wilderness Lands digitized include Designated Wilderness Lands, Lands Administratively Endorsed as Suitable · (prior to 

1981), Further Planning or Study Areas (Wilderness Study Areas (WSA's)), BLM Wilderness Inventory Not Completed, BLM Lands Under Appeal (WSA's), and USFS RARE II lands under 

litigation (California only). Each digitized tract, or 

polygon, was assigned (1) a numeric code identifying that polygon by State, wilderness category, 

and administering agency, and (2) a unique 

number identifying the polygon as a particular 

Wilderness Land. 

USGS PETROLEUM PROVINCES 

For the geologists to use the results of other petroleum ;assessment activities of the USGS, the 

spatial statistical units used in these previous 

studies were digitized. These units are assigned a 

numeric code identifying a unit by State, petroleum province number (as published in USGS 

Open-File Report 82-666-A, by Varnes and 

others, 1982), and a unique number identifying 

the individual polygons. 

B2 

GEOLOGIC REGIONS 

To assist the geologists in their initial estimates 

of the potential for petroleum in a particular Wilderness Land, the boundaries of geologic regions 

were digitized. The regions were interpreted by 

geologists for each State. These regions are identified by a numeric code indicating the rock type 

(for example, volcanics or crystalline) or tectonic 

type (for example, arch, dome, or basin) and a 

unique number identifying the polygon as a particular geologic feature (for example, Yellowstone 

volcanics or Wind River Basin). 

INTERMEDIATE PRODUCTS 

Once the digitizing was completed, several different intermediate products were generated. 

These working documents illustrated different aspects of the three data themes as well as the interrelationships between the themes. The two 

major groups of products generated include maps 

and tabular reports. Since all of these items were 

generated from one digitized data set, the products are consistent with each other. 

MAPS 

A variety of computer-generated maps was 

plotted. These maps illustrate the position, areal 

extent, and class of the features in each theme. 

When overlaid, the maps show the interrelationships between the different themes. For example, 

when the map of Wilderness Lands in a State is 

superimposed on the map of geologic regions for 

that State, all of the Wilderness Lands lying within any particular geologic region can be readily determined. This technique was useful in determining the initial qualitative estimates of petroleum 

potential for the wilderness areas. 

A set of three transparent film plots (Wilderness Lands, petroleum provinces, and geologic regions) was produced for each State. These plots, 

by-products of the quality control procedure for 

the digitizing activity, depict the boundaries of the 

data for each theme. Since the graphic is transparent, it can be easily used to view the relationship between the theme of the graphic and the 

data on an overlaid map. 
A paper map containing the boundaries of each 

petroleum province, the boundaries of each of the 

Wilderness Lands, and the numeric code for each 

wilderness area was produced for each State. This 

graphic has several purposes. The map illustrates 

which numeric code was associated with which 

plotted area on the map. Since the statistical reports for each wilderness area are keyed to the 

numeric code, this map allows the location of the 

reported data to be determined. This map clearly 

illustrates the occurrences of the petroleum provinces and Wilderness Lands for each State. 

These occurrences are an important relationship, 

since the sum of the petroleum potentials of the 

wilderness areas in a petroleum province may not 

exceed the previously determined petroleum potential of the entire province (Dolton and others, 

1981). Finally, the maps provide a convenient base 

map for the plotting of the boundaries of the different zones of qualitative petroleum potential assessments for the Wilderness Lands. 

A special map showing the different geologic regions was prepared for each State. On this 

graphic, the geologic regions thought not to have 

potential for petroleum (such as volcanic or crystalline rocks) were darkly shaded, and those regions thought unlikely to have potential for petroleum (such as mixtures of sedimentary and crystalline rock terranes) were lightly shaded. When 

this map is combined with the plots of the Wilderness Lands, the Wilderness Lands that are in 

these shaded regions (and therefore with a low 

or zero petroleum potential) can easily be seen. 

Finally, a map showing only · the Wilderness 

Lands was plotted for each State. This map illustrated the different categories of Wilderness 

Lands in each State and the Federal agency administering each tract. 

TABULAR REPORTS 

Two different statistical reports were generated 

from the digital data. These reports described the 

acreage of the data on the individual themes and 

the acreage of the areas where the different Wilderness Lands, petroleum provinces, and geologic 

regions were coincident. 

The first report contains the acreage calculated 

for each digitized polygon of the Wilderness Land, 

petroleum province, and geologic region theme in 

each State. For the Wilderness Lands, additional 

acreage summaries by wilderness category and 

administering Federal agency exist for each State. 

These figures were used in the potential assessment activities and were compared to the acreages compiled for the Wilderness Lands by other 

Federal agencies. 

The second report describes the occurrence of 

different petroleum provinces and geologic region 

combinations coincident with each wilderness 

area. This document reports the acreage of each 

unique petroleum province versus type of geologic 

region occurrence within each Wilderness Land 

and assists in the determination by the geologists 

of the petroleum potential of that Wilderness 

Land. To prepare the report, the data for the different themes in each State were converted to a 

raster data organization on a common coordinate 

system. The three raster data sets were then combined into one data set. Each cell in the resulting 

set has three observations (wilderness tract 

number, petroleum province number, and geologic 

region number). The number of unique occurrences of wilderness, petroleum province, and 

geologic region numbers was calculated. This 

number of unique occurrences was converted· to an 

acreage based on the size of the cell. 

A tabular report of the locations and histories of 

wells in the vicinity of each wilderness tract was 

also produced with the aid of the digital data. This 

work, performed under contract, used the digitized outline of each wilderness tract as the 

basis for querying a data base of the wells in each 

State. The location and history of the wells in the 

vicinity of each wilderness tract were extracted 

and reported. This technique saved a great deal of 

time, since the alternative to this automated spatial search was a manual sifting through all of the 

well records for each State. 

B3 

QUALITATIVE PETROLEUM ASSESSMENT 

REPORTING 

DIGITAL ACTIVITIES 

The geologists performing the assessments used 

the maps and tables described a:bove to map the 

qualitative petroleum potential for each of the 
Wilderness Lands. A wilderness tract could have 

one or more qualitative assessment zones (indicating if that portion of the wilderness tract had 

high, medium, low, low to zero, zero, or unknown 

petroleum potential). After the maps were compiled, these zone boundaries were added to the 

Wilderness Lands digital data. These new data allowed the generation of two additional products. 

Computer-generated maps showing different 

combinations of wilderness area petroleum potential, wilderness status, and administering Federal 

agency information were created at different 

scales. These maps show the final results of the 

qualitative assessment activities. These graphics 

are also the base maps from which the printed petroleum potential map series was compiled. 

A tabular report indicating the acreage of the 

petroleum potential zones for each wilderness area 

was created. This report included summary statistics describing the number of acres of each qualitative potential category by administering agency 

and wilderness status. 

Due to the interpretive nature of the petroleum 

assessment information, many revisions of the 

original digitized assessment data were required. 

Updated maps and statistical tables were needed 

with each revision. The digital techniques provided a quick, efficient means to update the information and to provide the needed maps and statistics. 

PUBLISHED MAP SERIES 

A series of printed maps provides a supplement 

to this report (Miscellaneous Investigations Series 

Maps, I-1537-I-1547, in press). These State 

maps describe the location and qualitative petroleum potential of the Wilderness Lands studied, 

the USGS petroleum provinces for each State, and 

other base information about the State. These 

maps were compiled by using traditional cartographic techniques. 

The Bureau of Land Management Wilderness 

Status Maps (1981a-j) are the bases on which the 

assessment information was compiled. These 

maps, which already have the Wilderness Lands 

and a great deal of other supplemental information 

compiled, provided a convenient starting point for 

the new map series. The cartographers transferred the boundaries of the petroleum provinces 

from digitally produced graphics to the BLM base 

maps. The qualitative petroleum potential information was transferred from the computergenerated maps previously described. 

SUMMARY 

The digital cartographic techniques proved to 

be of great use in the petroleum resource assessment program for the Wilderness Lands. The 

techniques provided plots for many different maps 

that illustrated various aspects of the data of interest. In addition to these graphic products, 

many different statistical and tabular reports 

were created. The techniques handled the data in 

a consistent manner and were quicker, more precise, and more versatile than comparable manual 

methods. 

REFERENCES CITED 

American Petroleum Institute, 1981, Federal Land Status of 

Washington, from API Federal Land Status Map Series 

for the western United States, American Petroleum Institute, Washington, D.C., scale 1:1,000,000 (1 sheet). 

Bureau of Land Management, 1981a, Wilderness Status Map, 

State of AriZona, ·u.S. Department of the Interior, 

1:1,000,000 (1 sheet). 

--1981b, Wilderness Status Map, State of California, U.S. 

Department of the Interior, 1:1,000,000 (1 sheet). 

--1981c, Wilderness Status Map, State of Colorado, U.S. 

Department of the Interior, 1:1,000,000 (1 sheet). 

--1981d, Wilderness Status Map, State of Idaho, U.S. Department of the Interior, 1:1,000,000 (1 sheet). 

--1981e, Wilderness Status Map, State of Montana, U.S. 

Department of the Interior, 1:1,000,000 (1 sheet). 

--198lf, Wilderness Status Map, State of Nevada, U.S. 

Department of the Interior, 1:1,000,000 (1 sheet). 

--1981g, Wilderness Status Map, State of New Mexico, 

U.S. Department of the Interior, 1:1,000,000 (1 sheet). 

--1981h, Wilderness Status Map, State of Oregon, U.S. 

Department of the Interior, 1:1,000,000 (1 sheet). 

--1981i, Wilderness Status Map, State of Utah, U.S. Department of the Interior, 1:1,000,000 (1 sheet). 

--1981j, Wilderness Status Map, State of Wyoming, U.S. 

Department of the Interior, 1:1,000,000 (1 sheet). 

Dolton, G. L., Carlson, K. H., Charpentier, R. R., Coury, A. 

B., Crovelli, R. A., Frezon, S. E., Khan, H. S.,Lister, J. 

H., McMullin, R. H., Pike, R. S., Powers, R. B., Scott, 

E. W., and Varnes, K. L., 1981, Estimates of Undiscovered Recoverable Conventional Resources of Oil and Gas 

in the United States, U.S. Geological Survey Circular 860, 

87 p. 

Varnes, K. L., Charpentier, R. R., and Dolton, G. L., 1982, 

Conditional estimates and marginal probabilities for undiscovered recoverable oil and gas resources by provincestatistical background data for U.S. Geological Survey 

Circular 860, USGS Open-File Report 82-66~A, USGS, 

Denver, Colorado, 29 p. 

B4