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D6168-97 – Standard Test Method Technical Guide
🗺️ Geoscience Location Types and Coordinate Systems
ASTM D6168‑97 (Reapproved 2010) establishes the fundamental framework for identifying geoscience data collection points. The guide mandates that every unique location can be defined by X (easting/latitude), Y (northing/longitude), and Z (altitude/elevation) coordinates. The specific additional information required depends on the geometric nature of the location.
The standard explicitly defines four distinct location types to accommodate the diverse geometries of field sites:
| 🟦 Type | 📏 Description | 🎯 Coordinate Model | ⚡ Example |
|---|---|---|---|
| 1. Single Position | A unique point defined by finite X, Y, and Z coordinates. | Single X, Y, Z triplet | Groundwater monitoring well (Lat, Lon, Altitude) |
| 2. Vertical Multiple | A single X, Y coordinate pair with multiple vertically oriented Z coordinates. | Finite X, Y + multiple Z values | Soil sampling site with multiple depth intervals |
| 3. Non‑Vertical Multiple | A single surface X, Y coordinate pair with multiple Z coordinates that are not vertically oriented. | Multiple X, Y, Z sets or deviation data | Slanted borehole |
| 4. Extended Area | Features with a considerable horizontal dimension that cannot be represented by a single finite X, Y coordinate. | Single Z + geometric boundaries | Sinkhole, waste disposal pit, mine, archaeological site |
💡 Guideline Note: For Type 2 locations (vertical multiples), the standard recommends using distinct Z coordinates (altitudes) for the upper and lower limits of a sampling interval rather than vertical intervals measured from the surface. This practice ensures precise depth correlation across a project.
📋 Minimum Set of Data Elements for Comprehensive Cataloging
Beyond the spatial coordinate framework, ASTM D6168‑97 mandates a minimum set of descriptive data elements to ensure robust identification, retrieval, and file organization of geoscience data. These elements add critical context to the raw coordinate data.
| 📂 Element Category | 🔍 Purpose and Description |
|---|---|
| Political Entities | Identifies the jurisdiction of the location (e.g., nation, state, county). This is essential for regulatory compliance and data management based on political boundaries. |
| Data Sources | Documents the origin of the information, including the responsible agency, project name, publication, or individual investigator who collected the data. |
| Individual Characteristics | Captures unique site-specific attributes such as a local site identifier, the purpose of the investigation, and specific physical characteristics of the location as described in Section 1.3 of the standard. |
⚡ Critical Consideration for Complex Sites: When cataloging Type 3 or Type 4 locations (e.g., a slanted borehole or a large landfill), catalogers must establish a consistent treatment method. The standard permits treating each unique sub‑point as an independent location or, for Type 3 locations, describing the horizontal deviation