Pamela Dunlap Derkey, as project chief and GIS coordinator, envisioned, managed and coordinated the GIS (geographic information systems) aspects of the regional geologic map compilation (NR_GEO dataset). Her work efforts focused on preparation of standardized spatial databases for the individual geologic map components, spatial database design, report writing, metadata (including refinement of attribute definitions), and quality checking the final GIS products. She provided input for revisions to GIS and metadata.
Robert J. Miller merged polygon and arc topology into a single spatial data file (ESRI® coverage) for many of the digital geologic maps. He also rubbersheeted all of the geologic quadrangle maps to their mathematically generated boundaries and all maps with state boundaries to 1:100,000-scale state boundary vector data. Miller wrote a variety of programs (1) to proof the individual quadrangle and national forest spatial databases for arc and polygon coding errors, (2) to manage spatial databases for the same areas that were revised in parallel so as to spatially incorporate new fields and their attributes from one version into another set of significantly updated spatial databases, and (3) to append forty-three geology map databases together in a specific sequence (to reflect priorities of one map over another) to create the regional compilation.
J. Douglas Causey developed and managed an in-house Access® relational database of map unit attribute information. He incorporated identification fields into each of the quadrangle and national forest ArcInfo® spatial databases and populated them, so each could be linked to the relational database that contained detailed geologic information. Causey reviewed the stratigraphic status of all the terms used to name geologic units using the USGS geologic names lexicon, attributed the field UNIT_TYPE in the look-up table NR_GEO.MU, and revised unit names to conform to usage specified for formal and informal stratigraphic units. Causey also managed all the information related to the age of geologic units. He converted all time units to geochronologic terms, checked consistency in coding, and created generalized time terms that are used to develop map symbols and to symbolize the database. Causey also incorporated map unit descriptions into the relational database. Causey developed a master reference list for all the map unit descriptions with assistance from Jeremy C. Larsen (contractor), Jeremiah Drewel (student), and Richard D. West (student). He indexed words in the map unit names and the map unit descriptions. He developed queries to check the integrity and quality of attribute information and to manipulate hierarchical data in the relational database. Information from the relational database was used to create the files that summarize map unit information in ArcInfo® look-up tables (NR_GEO.MU, NR_GEO.LITH, and NR_GEO.UN).
Arthur A. Bookstrom provided a new interpretation of the igneous map units and prepared the new igneous rock information for inclusion in the spatial database. Jeremy C. Larsen and Michael L. Zientek assisted with the review and revision of this information.
Mary H. Carlson (contractor) was responsible for incorporating revisions into the spatial databases and metadata. Carlson managed the data structure (arc and polygon feature attribute tables) of each of the quadrangle and national forest spatial databases (map tile) so that they could be appended together to generate a single regional database. Carlson worked with Arthur A. Bookstrom to initially capture igneous attribute information in shapefiles, and she worked with Robert J. Miller to join both igneous arc and polygon attributes, present in shapefile format, to each spatial database (map tile). Carlson created the NR_GEO.IGPNAM and NR_GEO.IGANAM ArcInfo® lookup tables from dBASE-format tables of igneous attribute information. With assistance from Miller, Carlson was able to append each individual spatial database together into one spatial database for the entire project area as the map tiles were revised. Gregory N. Green, William N. Kelley (contractor), and Mary H. Carlson (contractor), converted the attribute tables of previously prepared, digital geologic maps (generated by the Idaho Geological Survey, Montana Bureau of Mines and Geology, and USGS) into a standardized format, with assistance from Michael Koenig (student).
Thomas P. Frost devised map symbols (stored in the LAB_ASC and LAB_GAF items) for the item NAME in the NR_GEO.MU ArcInfo® look-up table. Frost was responsible for reviewing the consistency of the attributes reported in the fields LNAME_DOM and UNAME_DOM in the NR_GEO.LITH and NR_GEO.UN ArcInfo® look-up tables.
David E. Boleneus, Arthur A. Bookstrom, J. Douglas Causey, Karl V. Evans, Thomas P. Frost, Rebecca Pitts (student), Bradley S. Van Gosen, Anna B. Wilson, and Michael L. Zientek coded lithologic information in the in-house Access® relational database.
Karl V. Evans was responsible for reviewing the consistency of the attributes reported in the fields NAME_MAJOR, NAME_MAJR1, NAME_MAJR2, NAME_MINOR, and NAME_OTHER in the NR_GEO.LITH and NR_GEO.UN ArcInfo® look-up tables.
Jeremy C. Larsen and Kenneth C. Assmus (contractors) prepared rectified images of the geologic maps used to create the regional spatial database compilation. These images were used to proof the attribution of the spatial database.
Helen Z. Kayser (contractor) and Pamela Dunlap Derkey proofed and revised the attributes for the items NAME_OR, LAB_ASC_OR, LAB_GAF_OR, MINAGE_OR, and MAXAGE_OR in the map unit (NR_GEO.MU) look-up table and all of the attributes in the linecode (NR_GEO.LCD) look-up table. Kayser incorporated some of the information directly info the feature attribute tables (*.AAT and *.PAT) via a join process.
Kenneth C. Assmus (contractor) prepared ArcGIS® layer files (*.LYR) to symbolize the NR_GEO spatial database, and he prepared many of the page-size illustrations for the report that accompanies the spatial database.
QUALITY CONTROL Each spatial database (for a map tile) was proofed (prior to trying to compile the map tiles) to make sure that they were all in a geographic decimal second coordinate system, that all lines and polygons were attributed with a line or unit code, that the master map-unit look-up table contained the correct map label and unit name information, and that the information in the added identifier fields was correct. If we suspected a problem in line or polygon coding, the spatial databases were compared onscreen to georeferenced TIFF images of the original source maps and corrections to the spatial databases were made as warranted.
After the compilation was created for the first time, much proofing by many of the authors ensued over the span of a year (August 2003 through September 2004) to ensure that the spatial database for the regional compilation was ready to submit for technical review for publication: both the individual databases and the programs were revised and the databases re-compiled at least five times before the regional compilation passed a variety of quality-control checks.
Early on it was noticed that geologic units were named inconsistently between map tiles some corrections could be made by revising attribute tables. However, it was not until the forty-three map tiles were appended into a regional compilation that proofing the geologic names could be completed. The regional compilation was symbolized on NAME in ArcMapú and discrepancies were noted along the map boundaries. Depending on the context, NAME was revised. In the process of checking the boundary discrepancies, coding errors were found in the regional compilation. These were corrected in the individual map tiles. Again, a new source number was assigned for new source maps (and coding of the arcs or polygons reflect this new number).
A routine (programmed in an Arc Macro Languageú text file) was run on the regional map compilation to locate arcs that were coded incorrectly with regard to geology. Although the routine was run on the regional compilation the errors were fixed in the individual map tiles, subsequently another compilation was run after the errors were fixed. Because the routine was run on the compilation, not all arcs in the tiles were tested for these errors. There are several areas of overlap so map precedence was determined; areas with a lower precedence were removed from the compilation. Any errors that may be in the removed areas would not have been detected. The routine located and tagged lines coded as (1) contacts with the same map unit on both sides, (2) approximately located contacts with the same map unit on both sides, (3) dangling contacts in the middle of a map unit, and (4) dangling contacts with queried locations in the middle of a map unit. Each error was reviewed by comparing the spatial database to the paper source map or on-screen to a georeferenced TIFF image of the source map. Sometimes the error identified by the routine was an error in the original source map; in this case other source maps were used to interpret and correct the error. Other times it was an error in coding the original spatial database to match the source map. Arcs and polygons were recoded, deleted or sometimes added to match the source map. A new source number was assigned to additional source maps if coding or linework helped resolve one of the errors. The arcs or polygons edited during this process, due to new information or interpretation by the authors, was assigned this new source number.
Proofing then focused on the individual spatial database (map tile) boundaries and water bodies. We found that arcs defining map tile boundaries were inconsistently coded. Tile boundaries were coded with a variety of attributes (state, scratch, longitude and latitude); they were all re-coded to a single value "map boundary". In the process of checking the boundary discrepancies, arcs within the map tiles were found to be coded incorrectly as boundaries. The original sources were reviewed and appropriate corrections made.
Further corrections and revisions were made (December 2004 through June 2005) to NR_GEO (and the metadata) subsequent to technical reviews by Bruce R. Johnson, Steven E. Box, Nora B. Shew, Peter N. Schweitzer, and Lorre A. Moyer of the U.S. Geological Survey; Loudon R. Stanford and Reed S. Lewis of the Idaho Geological Survey; Karen Porter of the Montana Bureau of Mines and Geology; and Ryan Portner of the U.S.D.A. Forest Service.
MAP TILES We designed a regional compilation that used "puzzle pieces" or "map tiles" with fixed boundaries, so that a compilation could be easily built and updated. If a new map tile were to be added or to take the place of another, we wanted that piece to fit exactly without generating holes (unlabeled sliver polygons) along map tile boundaries or inadvertently replacing parts of the adjacent map tiles. A fixed boundary could either follow mathematically-generated lines of latitude and longitude and/or irregular boundaries. Most of the original databases were created for topographic map quadrangles which utilize lines of latitude and longitude for map boundaries. Some of the databases incorporated boundaries that followed irregular features (for example, state boundaries along crests of mountain ranges or centerlines of rivers; administrative boundaries of national parks and forests). MERGING TOPOLOGIES (for individual map tiles) Line and polygon topologies were merged (using Workstation ArcInfo®) for all spatial databases that originally contained line information (faults, dikes, and fold features) in one or more files and polygon information (geologic map unit features) in another. The resultant lines and polygons were spatially revised in areas where faults did not properly match up (become coincident) with contacts between map units. Two different procedures were used, as discussed below, for merging faults that were coincident with contacts and for merging faults that were not coincident with contacts (but should have been).
Scenario A. Merging faults that were COINCIDENT with contacts: The faults in the fault coverage were buffered at a distance of 20 meters. The buffer coverage was used to select the duplicate arcs in the geologic unit coverage, and the selected arcs were deleted. The fault arcs were imported into the geologic unit polygon coverage. Dangling contacts in the polygon coverage were extended to intersect the imported faults, and topology was rebuilt. The original geologic unit coverage was intersected by the updated version to produce label points that were then used to label the combined line and polygon coverage. Polygon label attributes of the rebuilt coverage were digitally compared to the original to verify that no errors had been introduced.
Scenario B. Merging faults that were NOT COINCIDENT with contacts (but should have been). In this situation, if a fault and a contact were nearly coincident (+/- about 100 meters), the contact was eliminated, and the remaining (replacement) arc retained the attribute coding inherited from the fault coverage: An initial buffer coverage for faults was built using a buffer distance of 50 meters. This buffer coverage was intersected with the geologic unit polygon coverage, thus creating nodes at the approximate ends of sections of arcs in the polygon coverage that are duplicated by faults. A second buffer coverage for faults was built using a buffer distance of 75 meters. This buffer coverage was used to select the duplicate sections of arcs created in the previous intersection step, and the selected arcs were deleted. Then the fault arcs were imported into the polygon coverage. Dangling contacts in the updated coverage were extended to intersect the imported faults. Extensive proofing and editing ensued to insure that the geologic unit polygons closed properly against the introduced fault arcs. The original geologic unit coverage was intersected by the updated version to produced label points that were then used to label the combined line and polygon coverage. Polygon label attributes of the resultant coverage were digitally compared to the original to verify that no errors had been introduced.
RUBBERSHEETING the GIS (for individual map tiles) Once a unified topology had been created, the databases, exclusive of those that used administrative boundaries, were converted to a geographic coordinate system (decimal seconds) and rubbersheeted either to mathematically-generated boundaries of latitude and longitude or to state boundaries derived from 1:100,000-scale digital line graph (DLG) files.
STANDARDIZING DATABASES (for individual map tiles) All of the source-map databases were then converted to a standard database structure that uses a standard set of attributes for each item (field) in the database. Individual look-up tables were removed from the spatial databases and the information was merged into master look-up tables. Several fields from these master look-up tables were physically added to the line and polygon feature attribute tables, so that the staff scientists could easily identify line types and map units by a map label or name throughout the course of preparing the regional compilation. Arcs were numerically coded by line type and polygons were numerically coded by map unit. In addition, for arcs that utilize an asymmetric line decoration (for example, thrust teeth), line direction was adjusted to accommodate a right-reading lineset of line decorations. ArcInfo® look-up tables were built to hold brief, descriptive information about lines (contacts, faults, folds, and dikes), polygons (map unit labels, names, lithology, geologic ages, igneous rock unit information), and map-source references. Paper plots were made and visually compared with the original source maps. Revisions were made to line and polygon coding and to line placement and direction; however, line directionality is the weakest part of the spatial database. Due to time and cost constraints, we focused on making sure that the polygons were correctly attributed rather than proofing all of the arcs for coding and line directionality. Please realize that many arcs may still not be properly oriented.
GEOLOGIC MAP DATA MODEL (Access® database) Work progressed in parallel to create a Microsoft Access® relational database to hold more detailed geologic information about the map units. A single identifier field (or item) was added to the ArcInfo® spatial databases and populated in order to join additional geologic information from the Access® relational database.
IGNEOUS ROCK DATA As the individual spatial databases (in ESRI® coverage format) were being prepared, line and polygon shapefiles were created from each coverage so that Arthur A. Bookstrom could update the shapefiles with new igneous rock interpretations. The shapefile theme tables were edited to add attribute information related to igneous rocks. Polygon data in the updated igneous rock shapefiles were then joined to the geologic map spatial databases (in ESRI® coverage format) using a custom Arc Macro Languageú program. The program first converted the polygon shapefiles to coverages, then added centroid labels to the polygons, and finally performed a spatial join (using the centroid labels of both the "from" and the "to" coverages) to add the new igneous rock items and attributes to the original coverages. During this join process, the ArcInfo® CLEAN command was performed twice using a minimal dangle tolerance of 0.00000000001 to ensure that lines would not shift (and thus degrade the horizontal resolution of the spatial data). Line data for dikes in the updated igneous rock shapefiles were manually added to the original coverages. Extensive proofing of the resultant coverages (spatial databases) then ensued, and revisions were made as needed. Generally, corrections had to be made in those files where Bookstrom had been provided with shapefiles created from preliminary spatial databases. There were several instances where the shape of the polygons and placement of lines had been subsequently revised by the original source-map authors, thus the location of the polygon centroid labels in the revised spatial databases did not match the location of the polygon centroid labels in the coverages derived from the igneous rock shapefiles, and the spatial join did not join the correct igneous information to the proper map polygon. After the igneous attributes were incorporated into the individual spatial databases (map tiles), the attributes could be proofed spatially in a single spatial database in which all 43 map tiles were combined. Minor errors and inconsistencies in igneous coding and table structure were noted. A unique identification field was created for each spatial object in each of the map tiles. Using the XTools extension, unique identifier and igneous attribute data were pulled from each of the forty-three spatial databases directly into three Excel® spreadsheets for editing (one for polygons and two for the arcs). After proofing the data in the spreadsheets for internal consistency and revising the files as needed, the igneous rock information was incorporated back into the individual spatial databases (using the unique identification number for the join item).
REGIONAL COMPILATION - map precedence An Arc Macro Languageú program was written to combine the forty-three individual spatial databases into a single spatial database. For areas covered by more than one source map, a group of scientists familiar with the geology of the region and with the source maps decided which map should take precedence over another.
A. For the SOUTHERN PART of the area (central Idaho and southwest Montana), areas of overlap were managed accordingly: A1. The first map tile incorporated into the regional compilation was the Hailey-Idaho Falls map (Worl and Johnson, 1995); A2. The next map tile incorporated into the regional compilation was the Challis National Forest map (Wilson and Skipp, 1994), and it replaced the geology for the Hailey-Idaho Falls map (Worl and Johnson, 1995) in areas of overlap; A3. Then the Hailey-Challis map (Link and others, 1995) was incorporated into the regional compilation. It replaced the geology of both the Hailey-Idaho Falls (Worl and Johnson, 1995) and Challis National Forest (Wilson and Skipp, 1994) maps in areas of overlap; A4. Geology from the Idaho City map (Kiilsgaard and others, 2001) was subsequently incorporated into the regional compilation, and it replaced the geology for the Hailey-Idaho Falls map (Worl and Johnson, 1995) in areas of overlap; A5. The Challis quadrangle map (Fisher and others, 1992) was incorporated next. It replaced the geology for both the Challis National Forest (Wilson and Skipp, 1994) and the Hailey-Challis (Link and others, 1995) maps in areas of overlap; A6. The Dillon (Ruppel and others, 1993), Leadore (Ruppel, 1998), and Nez Perce Pass (Lewis and Stanford, 2002e; Berg and Lonn, 1996) maps were then incorporated into the regional compilation; A7. Then geology from the Salmon National Forest map (Evans and Green, 2003) was incorporated. It replaced the geology from the Challis quadrangle (Fisher and others, 1992), Challis National Forest (Wilson and Skipp, 1994), Dillon (Ruppel and others, 1993), Leadore (Ruppel, 1998), and Nez Perce Pass (Lewis and Stanford, 2002e; Berg and Lonn, 1996) maps in areas of overlap; A8. Next, geology from the Elk City (Lewis and Stanford, 2002a) and Riggins (IGS, unpub. data, 1996) maps were incorporated; A9. Lastly, the Payette National Forest map (Lund, in press) was incorporated. It replaced the geology from the Challis quadrangle (Fisher and others, 1992), Elk City (Lewis and Stanford, 2002a), Riggins (IGS, unpub. data, 1996), and Salmon National Forest (Evans and Green, 2003) maps in areas of overlap.
B. In the EASTERN PART of the area (central Montana), areas of overlap were managed as follows: B1. The first map tile incorporated into the regional compilation for central Montana was for the Gallatin National Forest (Green and others, 1999); B2. Geology from the Livingston map (Berg, Lopez, and Lonn, 2000) was incorporated next. It replaced that from the Gallatin National Forest map (Green and others, 1999) in areas of overlap; B3. The Butte (Lewis, 1998a) and Choteau (Mudge and others, 2001) map tiles were added next; B4. Then the Helena National Forest map (Green and Tysdal, 1996) was incorporated. It replaced the geology from the Butte (Lewis, 1998a), Choteau (Mudge and others, 2001), and Gallatin National Forest (Green and others, 1999) maps in areas of overlap.
C. For the NORTH-CENTRAL PART of the area (Wallace area), areas of overlap were managed as follows: C1. The Wallace 1:250,000-scale map (Harrison, Griggs and others, 2000) was incorporated first into the regional compilation for the north-central part of the area; C2. Then the geology from the Thompson Falls (Lewis and Derkey, 1999) and the Wallace 1:100,000-scale (Lonn and McFaddan, 1999; Lewis and others, 1999) maps were incorporated. The geology from these three maps replaced that from the Wallace 1:250,000-scale map (Harrison, Griggs and others, 2000) in areas of overlap.
IN OTHER WORDS, in areas of overlap: (1) the Challis National Forest map (Wilson and Skipp, 1994) takes precedence over the Hailey-Idaho Falls map (Worl and Johnson, 1995); (2) the Hailey-Challis map (Link and others, 1995) takes precedence over the Hailey-Idaho Falls (Worl and Johnson, 1995) and Challis National Forest (Wilson and Skipp, 1994) maps; (3) the Idaho City map (Kiilsgaard and others, 2001) takes precedence over the Hailey-Idaho Falls map (Worl and Johnson, 1995); (4) the Challis map (Fisher and others, 1992) takes precedence over the Challis National Forest (Wilson and Skipp, 1994) and the Hailey-Challis (Link and others, 1995) maps; (5) the Salmon National Forest map (Evans and Green, 2003) takes precedence over the Challis quadrangle (Fisher and others, 1992), Challis National Forest (Wilson and Skipp, 1994), Dillon (Ruppel and others, 1993), Leadore (Ruppel, 1998), and Nez Perce Pass (Lewis and Stanford, 2002e; Berg and Lonn, 1996) maps; (6) the Payette National Forest map (Lund, in press) takes precedence over the Challis (Fisher and others, 1992), Elk City (Lewis and Stanford, 2002a), Riggins (IGS, unpub. data, 1996), and Salmon National Forest (Evans and Green, 2003) maps; (7) the Livingston map (Berg, Lopez, and Lonn, 2000) takes precedence over the Gallatin National Forest map (Green and others, 1999); (8) the Helena National Forest map (Green and Tysdal, 1996) takes precedence over the Butte (Lewis, 1998a), Choteau (Mudge and others, 2001), and Gallatin National Forest (Green and others, 1999) maps; (9) the Thompson Falls (Lewis and Derkey, 1999) and Wallace 1:100,000-scale maps (Lonn and McFaddan, 1999; Lewis and others, 1999) replaced that from the Wallace 1:250,000-scale map (Harrison, Griggs and others, 2000).
QUALITY CONTROL Each spatial database (for a map tile) was proofed (prior to trying to compile the map tiles) to make sure that they were all in a geographic decimal second coordinate system, that all lines and polygons were attributed with a line or unit code, that the master map-unit look-up table contained the correct map label and unit name information, and that the information in the added identifier fields was correct. If we suspected a problem in line or polygon coding, the spatial databases were compared onscreen to georeferenced TIFF images of the original source maps and corrections to the spatial databases were made as warranted. After the compilation was created for the first time, much proofing by many of the authors ensued over the span of a year (August 2003 through September 2004) to ensure that the spatial database for the regional compilation was ready to submit for technical review for publication: both the individual databases and the programs were revised and the databases re-compiled at least five times before the regional compilation passed a variety of quality-control checks.
Early on it was noticed that geologic units were named inconsistently between map tiles some corrections could be made by revising attribute tables. However, it was not until the forty-three map tiles were appended into a regional compilation that proofing the geologic names could be completed. The regional compilation was symbolized on NAME in ArcMapú and discrepancies were noted along the map boundaries. Depending on the context, NAME was revised. In the process of checking the boundary discrepancies, coding errors were found in the regional compilation. These were corrected in the individual map tiles. Again, a new source number was assigned for new source maps (and coding of the arcs or polygons reflect this new number).
A routine (programmed in an Arc Macro Languageú text file) was run on the regional map compilation to locate arcs that were coded incorrectly with regard to geology. Although the routine was run on the regional compilation the errors were fixed in the individual map tiles, subsequently another compilation was run after the errors were fixed. Because the routine was run on the compilation, not all arcs in the tiles were tested for these errors. There are several areas of overlap so map precedence was determined; areas with a lower precedence were removed from the compilation. Any errors that may be in the removed areas would not have been detected. The routine located and tagged lines coded as (1) contacts with the same map unit on both sides, (2) approximately located contacts with the same map unit on both sides, (3) dangling contacts in the middle of a map unit, and (4) dangling contacts with queried locations in the middle of a map unit. Each error was reviewed by comparing the spatial database to the paper source map or on-screen to a georeferenced TIFF image of the source map. Sometimes the error identified by the routine was an error in the original source map; in this case other source maps were used to interpret and correct the error. Other times it was an error in coding the original spatial database to match the source map. Arcs and polygons were recoded, deleted or sometimes added to match the source map. A new source number was assigned to additional source maps if coding or linework helped resolve one of the errors. The arcs or polygons edited during this process, due to new information or interpretation by the authors, was assigned this new source number.
Proofing then focused on the individual spatial database (map tile) boundaries and water bodies. We found that arcs defining map tile boundaries were inconsistently coded. Tile boundaries were coded with a variety of attributes (state, scratch, longitude and latitude); they were all re-coded to a single value "map boundary". In the process of checking the boundary discrepancies, arcs within the map tiles were found to be coded incorrectly as boundaries. The original sources were reviewed and appropriate corrections made. The database structure of the various look-up tables was refined frequently throughout the process of creating the regional compilation. Items were added, removed or combined to create look-up tables that were more user friendly.
Further corrections and revisions were made (December 2004 through June 2005) to NR_GEO (and the metadata) subsequent to technical reviews by Bruce R. Johnson, Steven E. Box, Nora B. Shew, Peter N. Schweitzer, and Lorre A. Moyer of the U.S. Geological Survey; Loudon R. Stanford and Reed S. Lewis of the Idaho Geological Survey; Karen Porter of the Montana Bureau of Mines and Geology; and Ryan Portner of the U.S.D.A. Forest Service.