FOCUS GROUP ASSESSMENTS OF
USER NEEDS AND RECOMMENDATIONS FOR GEOLOGIC MAPPING

QA/QC and Standardization

Geologic mapping should be produced or developed on the basis of a set of agreed-upon criteria meeting QA/QC standards so that products reach a specified level of professionalism. Metadata, reports and project information, standardized data categories, sampling locations, temporal sampling frequency, universal horizontal/vertical datum controls, and examples of proper and improper applications should ensure appropriate data use and interpretation by the geologic community and the public.

Map Scales

There is a demand for geologic mapping at a variety of spatial scales, depending on the interest of the user. Demands for mapping conforming with the standard 7.5-minute quadrangles and with different political boundaries will both exist. Mapping efforts should focus on satisfying the need to produce products at varying scales and on the ability to combine digital maps, which can conform to any boundary.

Digital Format

Maps and related attributes should be made available in digital format--which should include a variety of format options, metadata sets, and a user friendly format. They should be available on Internet, on CD, and through cooperative ventures that would make public access easier.

Customers

Customers for geologic data must be broadly defined as anyone making a land-use decision. Customers' input must be sought several times during data collection and the mapping process. Customer input should be used to develop interpretation of geologic information that is suited to user needs and is of the appropriate technical level.

Derivative Mapping

Producers of geologic maps need to present data but also analyses and interpretations for professional and nonprofessional users. Such products should include multiplatform data or a common, digital base of standard format, including geochemical, engineering, geologic hazard, and water and mineral resource characterization. In this way, derivative mapping (including geochemistry, engineering, hazards, and so on) may facilitate reasonable land-use planning decisions based on the integration of multiplatform (biologic, hydrographic, and geologic) information.

• Multiagency input from ecoregion mapping.
• Combine data from multiagency sources.Better correlation, including vertical integration, between maps
• Assessment of maps with respect to uncertainties and determination of error tolerances by use/user.

Standard Terminology

It is very important for the geologic community to standardize its use and meaning of terminology. We could adopt one of the existing standardized terminologies such as the American Society of Testing Materials (ASTM) soil classification system (formerly Unified Soil Classification System) or we could publish our own. However, for the resulting terminology to be most useful, the terminology we use needs to mean exactly the same thing to each person mapping in the field or using maps in the office. For example, silt and clay are often used interchangeably and incorrectly. It is almost impossible to guess how much sand is in a "sandy clay." Similar standardization should be used for the terminology of rock types. ["Lack of standard terminology is a detriment to proper use of geologic maps."]*

Brittle Structures--Fractures, Joints, Faults

Geologic maps should show the orientation, dimension, opening, and density of all fractures, joints, minor faults, and major faults. Rationale: Fracture information is important for permeability of ground water, pollutants, and radon.

Surface Hydrology

Runoff in urban density zones is strongly affected by the creation of artificial, impervious surfaces (sidewalks, roads, driveways). Also, data on watershed boundaries, stream gauge locations, and other stream characteristics like stream depths and locations of rapids and waterfalls are useful. ["In urban zones the run-off problems are immense."]*

Enhanced Geologic Maps and Enhanced Delivery Systems

Enhanced geologic maps are necessary from the standpoint of full-color, large-scale maps with enhanced data of all related features. This "enhanced data" should include mineral modal and bulk chemical compositions, grain size and sorting, and engineering properties of all mapped units. These data should be made available in a digital format and internet accessible for use in various GIS systems in Federal, State, local, and private land-planning agencies. ["Geologic maps should have more detailed descriptions of map units and site-specific information related to water and other issues. Using a GIS system, the user could download specific layers, not necessarily the whole ball of wax."]*

Ground-Water Hydrology

Ground-water aquifer depletion and recharge rates need to be made available on maps, along with historic, present, and future conditions for ground-water suppliers and public officials faced with balancing developers' plans with the public interest. Additional ground-water data should include background water quality, information on lithology and water-chemistry interaction by rock unit, ground-water flow including volume and direction, and the location of waste sites. ["Recharge rates should be made available on maps where the data are available. Background water quality, interaction between water and rocks, and direction of flow are also useful."]*

GPS and Geophysical Data: Topographic Maps

Topographic maps should have a GPS data base, with GPS stations located. Rationale: The topographic survey is the repository of the XYZ coordinates of our land surface. A very central piece of background information for seismic hazard assessment is the change of location of monuments with time. The USGS has many monuments for hydrological data collection, and some of these could be used as GPS monuments. ["Stream gauges should have precise locations as an important component of basic information. The USGS should develop a background GPS network."]*

Karst Features

Karst and associated features need to be mapped and documented because of their important impact on manmade facilities.

Ecological Data

A number of ecological parameters should be compiled in conjunction (as overlays) with a geologic map base. These ecological features are likely controlled by the geologic formation with which they are associated. Suggested opportunities include critical ecological areas, wetlands, coastal zones, and rare ecosystems. Information would be used for site assessments, land-use planning, and environmental protection. ["Although geologists may not be the best people to collect these data, some general information could be captured during geologic mapping, such as location of wetlands and so on."]*

Educational Maps

Maps compiling the locations of sites of geological, mineralogical, and fossil interest and of historical and modern waste sites should be produced for schools, hobbyists, economic development groups, and tourism agencies. ["Perhaps a GIS layer for information that could be digested by K-12."]*

Hazards Mapping

It is very important to compile data about geologic hazards. For example some geologic formations are closely associated with slope stability failures at slopes having vertical-to-horizontal ratios greater than 1:4. Where these units crop out within a 7.5-minute quadrangle, they should be identified. Other examples are sinkholes, colluvium/unstable slopes, previous mining activities, shrink-swell soils, and hazardous or solid waste sites. ["Some formations are susceptible to slope failure, sinkholes, and so on."]*

 

*Additions in brackets [ ] are from the presenter's oral remarks.

Basic Geologic Data--Surficial and Bedrock Geology

In addition to geologic data traditionally provided on geologic maps, this group would like more information. At a minimum, this should include--

• More strike and dip measurements.
• Surface and bedrock geology.
• Thickness of overburden (residual soils).
• Depth to bedrock (sediments overlying bedrock).
• Geologic structure of bedrock and soils.
• Block diagrams.
• More cross sections.

These categories should be standardized for presentation on geologic maps.

Geotechnical Data

Every geologic map should present relevant geotechnical information on the surface and bedrock geology. Some of this information can be presented as footnotes, annotations, and tables. Such data should, ideally, include--

• A table summarizing significant engineering properties of each mapped unit (for example, unconfined compressive strength, relative density, unit weight, friction angle, cohesion, Atterberg limits).
• Descriptions of soil and rock units (including residual soils) in accordance with American Society of Testing Materials (ASTM) and International Society for Rock Mechanics (ISRM) standards.
• Significant natural and manmade hazards, such as landslides, karst susceptibility, subsidence, shrink-swell potential, fill zones, contamination, abandoned mine workings.
• Significant geotechnical test boring locations.
• Geophysical and seismic data.

Presentation/Delivery Systems

Based on the needs assessment for geotechnical applications of geologic mapping, the following recommendations are being presented:

• Digital format should include multiple overlays of various geologic, hydrologic, geotechnical, and cultural features.
• Delivery system for the digital formats should be the World Wide Web as well as traditional methods. They should be available in both technical and layman's versions. Online help should be available for both versions.
• 7.5-minute mapping is the preferred or standard recommended, but specific projects may require scale to be tailored to needs.

Hydrogeologic Information

As a part of the digital format, there should be several layers of hydrogeologic information including--

• Ground-water elevations.
• Ground-water hydraulic properties.
• Recharge areas.
• Well-log data (including shallow wells).
• Geochemical data.
• Water-quality data.
• Pollution-potential data.

Educational Tools (Schools and Individuals)

1. Access to traditional and new modes (WWW) of distribution (quickly).

2. Online help and answers to frequently asked questions (FAQ); realistic references and their local sources.

3. Availability of data sets for schools (investigations) and community issues.

4. Location of classic sites (outcrops) within the mapped area (preservation and observation).

5. Present data for teacher utilization for classroom activities.

6. Historical utilization of past map models (top 10, USGS folio series, "Nature To Be Commanded...").

Historical, Physical, and Cultural Features of Significance

1. Historical data sets (maps, case studies, logs, hazards, anthropomorphic changes (manmade)).

2. Cultural features (points to past land use, landmarks).

3. Physical features:

• Buried land forms (stream valleys).
• Surface (drainage divides, watersheds).

4. Physical geography of the quadrangle (highlights).

---

Previous | CONTENTS | Next

---

This page is URL https://pubs.usgs.gov/circular/c1148/focusgroups.html
Last modified 15 April 1998
Maintained by John Watson and Kathie Watson