Isostatic gravity map of Yukon Flats, east-central Alaska

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Morin, R.L., 2002, Isostatic gravity map of Yukon Flats, east-central Alaska: U.S. Geological Survey Open-File Report 02-322, U.S. Geological Survey, Menlo Park, California.

   Online Links:

   • http://pubs.usgs.gov/of/2002/0322/

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -152.000
   East_Bounding_Coordinate: -141.000
   North_Bounding_Coordinate: 68.000
   South_Bounding_Coordinate: 65.000
   

3. What does it look like?

   http://geo-nsdi.er.usgs.gov/metadata/open-file/02-322/browse.png (PNG)

   Reduced-size image of the map sheet, 725x483 pixels, 114k bytes

   http://pubs.usgs.gov/of/2002/0322/pdf/of02-322.pdf (PDF)

   Printable version of the map sheet, 1.5 megabytes

4. Does the data set describe conditions during a particular time period?

   Calendar_Date: 2002

   Currentness_Reference:

   publication date

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: map
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a point data set.
   2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.01 minute. Longitudes are given to the nearest 0.01 minute. Latitude and longitude values are specified in Degrees and decimal minutes. The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: National Geodetic Vertical Datum of 1929 (NGVD29)
      Altitude_Resolution: 0.1
      Altitude_Distance_Units: feet
      Altitude_Encoding_Method: attribute values
      

7. How does the data set describe geographic features?

   table1.doc

   Principal facts (gravity observations)

   (stname)

   station identifier (text, 4 characters) identifier without scientific significance

   auxname

   (text, 4 characters) identifier without scientific significance

   latdeg

   degrees of latitude (integer)

   Range of values
   Minimum:	64
   Maximum:	67
   Units:	degrees
   Resolution:	1

   latmin

   minutes of latitude (number, 2 places to right of decimal)

   Range of values
   Minimum:	0.00
   Maximum:	59.90
   Units:	minutes
   Resolution:	0.01

   londeg

   degrees of longitude (integer)

   Range of values
   Minimum:	141
   Maximum:	151
   Units:	degrees
   Resolution:	1

   lonmin

   minutes of longitude (number, 2 places to right of decimal)

   Range of values
   Minimum:	0.00
   Maximum:	59.95
   Units:	minutes
   Resolution:	0.01

   elevft

   Elevation in feet

   Range of values
   Minimum:	154.2
   Maximum:	4722.0
   Units:	feet
   Resolution:	0.1

   obsgrav

   Observed gravity

   Range of values
   Minimum:	981929.03
   Maximum:	982383.30
   Units:	mgal
   Resolution:	0.01

   locsrc

   Location source code

   Value	Definition
   A	good location, modern published maps, scale 1:63,360
   B	poor location, modern published maps, scale 1:63,360
   F	good location, old or unpublished maps, scale 1:63,360
   G	poor location, old or unpublished maps, scale 1:63,360
   I	transfer from smaller-scale field map, old or unpublished maps, scale 1:63,360
   K	good location, modern 1:250,000 scale maps
   L	poor location, modern 1:250,000 scale maps

   gravsrc

   Gravity source code

   Value	Definition
   A	LaCoste & Romberg Geodetic meters: 3 ties within 0.1 mGal
   B	LaCoste & Romberg Geodetic meters: other multiple ties
   C	LaCoste & Romberg Geodetic meters: ties or drift loops lasting 6 hours
   D	LaCoste & Romberg Geodetic meters: ties or drift loops lasting 6-24 hours
   E	LaCoste & Romberg Geodetic meters: ties or drift loops lasting 1-4 days
   F	LaCoste & Romberg Geodetic meters: ties or drift loops lasting > 4 days
   G	Worden or World-Wide meters (loop drift control): 3 ties within 0.1 mGal
   H	Worden or World-Wide meters (loop drift control): other multiple ties
   I	Worden or World-Wide meters (loop drift control): ties or drift loops lasting 6 hours
   J	Worden or World-Wide meters (loop drift control): ties or drift loops lasting 6-24 hours
   K	Worden or World-Wide meters (loop drift control): ties or drift loops lasting 1-4 days
   L	Worden or World-Wide meters (loop drift control): ties or drift loops lasting > 4 days
   M	Worden or World-Wide meters (other drift control): 3 ties within 0.1 mGal
   N	Worden or World-Wide meters (other drift control): other multiple ties
   O	Worden or World-Wide meters (other drift control): ties or drift loops lasting 6 hours
   P	Worden or World-Wide meters (other drift control): ties or drift loops lasting 6-24 hours
   Q	Worden or World-Wide meters (other drift control): ties or drift loops lasting 1-4 days
   R	Worden or World-Wide meters (other drift control): ties or drift loops lasting > 4 days
   S	Worden or World-Wide meters (no drift control): 3 ties within 0.1 mGal
   T	Worden or World-Wide meters (no drift control): other multiple ties
   U	Worden or World-Wide meters (no drift control): ties or drift loops lasting 6 hours
   V	Old LaCoste & Romberg or other thermostated meters: 3 ties within 0.1 mGal
   W	Old LaCoste & Romberg or other thermostated meters: other multiple ties
   X	Old LaCoste & Romberg or other thermostated meters: ties or drift loops lasting 6 hours
   Y	Data from other agencies
   Z	Unstated reasons to expect errors

   elevsrc

   Elevation source code

   Value	Definition
   A	bench marks
   B	highway and railway surveys
   C	sea level
   D	special surveys
   E	US Weather Bureau, FAA, and U-Wisconsin surveys
   F	black map elevations
   G	brown map elevations
   H	blue map elevations
   I	elevations from unpublished maps
   J	river gradient interpolation, contour interval 0-50 ft
   K	river gradient interpolation, contour interval 100 ft
   L	river gradient interpolation, contour interval 200 ft
   M	good contour interpolation, contour interval 0-50 ft
   N	good contour interpolation, contour interval 100 ft
   O	good contour interpolation, contour interval 200 ft
   P	poor contour interpolation, contour interval 0-100 ft
   Q	poor contour interpolation, contour interval 200 ft
   R	Altimetry, good repeated readings, base distance < 15 miles
   S	Altimetry, good repeated readings, base distance 15-70 miles
   T	Altimetry, alticorder or other good base control, base distance < 15 miles
   U	Altimetry, alticorder or other good base control, base distance 15-70 miles
   V	Altimetry, poor control, base distance < 15 miles
   W	Altimetry, poor control, base distance 15-70 miles
   X	Altimetry, poor control, base distance > 70 miles
   Y	Altimetry involving special adjustments
   ?	no data
   @	Elevation from nearby bench marks
   $	Elevation from differential GPS
   %	Elevation from GPS

   sbaacc

   simple bouguer anomaly accuracy code

   Value	Definition
   1	gravity anomaly accuracy, milligals 0.01 Local surveys with special gravity meters and leveling
   2	gravity anomaly accuracy, milligals 0.02 Multiple readings with LaCoste & Romberg meters on hard, surveyed surfaces
   3	gravity anomaly accuracy, milligals 0.05 Average LaCoste & Romberg data at stable bench marks
   4	gravity anomaly accuracy, milligals 0.10 Average LaCoste & Romberg or Worden data at sea level or frost-affected bench marks
   5	gravity anomaly accuracy, milligals 0.2 Worden or LaCoste & Romberg data with poor drift or closure errors, or average data at vertical angle bench marks
   6	gravity anomaly accuracy, milligals 0.5 Data from loops with closure errors this large, or good data using river gradients, good photogrammetric elevations or well controlled altimetry
   7	gravity anomaly accuracy, milligals 1.0 Most surveys based on reasonable altimetry
   8	gravity anomaly accuracy, milligals 2.0 Data using moderate-distance altimetry in variable weather or spot elevations on 100-ft contour interval maps
   9	gravity anomaly accuracy, milligals 5.0 Data using long-range altimetry in bad weather or contour interpolation on 200-ft contour interval maps
   0	gravity anomaly accuracy, milligals >5.0 Data from surveys using long-distance altimetry or altimetry with control failures or errors or some 500-ft contour interval reconnaissance maps

   faa

   free-air anomaly (mgal)

   Range of values
   Minimum:	-75.08
   Maximum:	117.11
   Units:	mgal
   Resolution:	0.01

   sba

   simple bouguer anomaly (mgal)

   Range of values
   Minimum:	-98.67
   Maximum:	18.11
   Units:	mgal
   Resolution:	0.01

   iztc

   inner-zone terrain correction from station to 0.39 km to 0.01 milligal

   Range of values
   Minimum:	0.00
   Maximum:	0.00
   Units:	mgal

   tc

   terrain correction from 0.39 km to 166.7 km to 0.01 milligal

   Range of values
   Minimum:	-0.23
   Maximum:	25.37
   Units:	mgal
   Resolution:	0.01

   cba

   complete bouguer anomaly

   Range of values
   Minimum:	-88.99
   Maximum:	18.75
   Units:	mgal
   Resolution:	0.01

   ia

   isostatic anomaly

   Range of values
   Minimum:	-39.74
   Maximum:	62.08
   Units:	mgal
   Resolution:	0.01

   dataset

   text of 4 characters matching a value from the dataset table (table 2) identifier without scientific significance

   datum

   Datum code

   Value	Definition
   (no value)
   N	1967 ellipsoid and conversion of Barnes Alaska datum to IGSN-71 datum

   elev2ft

   second elevation in whole feet

   Range of values
   Minimum:	0
   Maximum:	4694
   Units:	feet
   Resolution:	1

   elev2src

   Second elevation source code (same meanings as for elevation source code)

   sba2elev

   simple Bouguer anomaly based on second elevation to 0.1 milligal

   Range of values
   Minimum:	-91.5
   Maximum:	78.5
   Units:	mgal
   Resolution:	0.1

   iacode

   isostatic anomaly code

   Value	Definition
   ISO	isostatic correction made from station to 166.7 km.
   ISOW	isostatic correction made for the whole earth

   table2.doc

   Data set

   dscode

   Data set code (text of 8 characters) identifier without scientific significance

   project

   Abbreviation (10 character) for name of project in which data set was created identifier without scientific significance

   traverse

   Abbreviation (15 character) for the traverse on which observations were collected identifier without scientific significance

   dsdate

   Date the data set was created coded dates, as MM/DD/YYYY where MM is the month, DD the day, YYYY the 4-digit year, leading zeros retained

   meter

   Gravity meter used identifier without scientific significance

   metertyp

   meter type

   Value	Definition
   0
   1
   2

   factor

   Meter factor

   Range of values
   Minimum:	0.00000
   Maximum:	1.00252
   Resolution:	0.00001

   gmt

   local time offset from GMT

   Range of values
   Minimum:	8
   Maximum:	11
   Units:	hours
   Resolution:	0.00001

   chief

   Name of project chief carrying out survey surnames

   obsrvrs

   Names of people involved in surveying (14 characters) surnames separated by commas, sometimes truncated

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Morin, R.L.
2. Who also contributed to the data set?
3. To whom should users address questions about the data?
   Robert L. Morin

   U.S. Geological Survey

   345 Middlefield Rd, MS 989

   Menlo Park, CA
   

   U.S.A.

   650-329-5320 (voice)

   morin@usgs.gov

Why was the data set created?

This map was produced to examine gravity anomalies associated with sedimentary basins in the area.

How was the data set created?

1. From what previous works were the data drawn?
2. How were the data generated, processed, and modified?

   Date: 1959 (process 1 of 3)

   The gravity data used to make this map were collected between 1959 and 1984. The data were collected by automobile, aircraft, and watercraft. Most of the data were collected as part of a U.S. Geological Survey (USGS) regional gravity data collection project. Some of the data were collected as part of other USGS local projects. One data set was collected by the NGS (National Geodetic Survey).

   Date: 2001 (process 2 of 3)

   data reviewed

   Date: 06-Aug-2003 (process 3 of 3)

   Creation of original metadata record Person who carried out this activity:
   

   Robert Morin

   U.S. Geological Survey

   USGS

   Menlo Park, CA
   

   USA

   650-329-5320 (voice)

   morin@usgs.gov

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?
   Observed gravity data are accurate to about 0.05 milligals.
2. How accurate are the geographic locations?
   Accuracy of the data is about 18 m.
3. How accurate are the heights or depths?
   
4. Where are the gaps in the data? What is missing?
   
5. How consistent are the relationships among the observations, including topology?
   Gravity anomalies were visually checked and reviewed at a scale of 1:500,000.
   This map was produced to be used at a map scale of 1:500,000.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: none
Use_Constraints: none

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey

   345 Middlefield Road

   Menlo Park, CA
   

   USA

   1-888-ASK-USGS (voice)
2. What's the catalog number I need to order this data set? USGS Open-File Report 02-322
3. What legal disclaimers am I supposed to read?

   Although this digital spatial data has been subjected to rigorous review and is substantially complete, it is released on the condition that neither the USGS nor the United States Government may be held liable for any damage resulting from its authorized or unauthorized use.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	Gravity measurements and associates survey data in format Microsoft Word Size: 0.5859
     Network links:	http://pubs.usgs.gov/of/2002/0322/table1.doc http://pubs.usgs.gov/of/2002/0322/table2.doc

     Data format:	Gravity measurements and associated survey data in format Shapefile (version 1.0) Size: 0.1055
     Network links:	http://geo-nsdi.er.usgs.gov/metadata/open-file/02-322/data.zip

   • Cost to order the data: none

Who wrote the metadata?

Dates:

Last modified: 10-Jun-2016

Metadata author:

Peter N Schweitzer

USGS Midwest Area

Collection manager, USGS Geoscience Data Clearinghouse, http://geo-nsdi.er.usgs.gov/

Mail Stop 954

12201 Sunrise Valley Dr

Reston, VA

USA

703-648-6533 (voice)

703-648-6252 (FAX)

pschweitzer@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)