Attribute_Accuracy:
Attribute_Accuracy_Report:
Because these data were digitized from printed contour maps that were drawn originally by researchers who produced the source materials, the values presented here should be regarded as approximate and faithful to the published interpretation (contouring) of the original instrument data. Factors affecting accuracy include the accuracy and precision of the original aircraft flight line navigation and elevation as well as the calibration of the instruments used to measure the magnetic field.
Logical_Consistency_Report:
In general each original map shows data collected by a single contractor or group responsible for collecting and processing the field observations, and reflect industry standard practices and controls as of the time period when the maps were published. Variation among surveys is possible, especially if they were carried out during very different time periods.
Completeness_Report:
Contouring, and subsequently digitizing of the contours, covered areas that included original flight line data, so these data may not extend into all parts of the original map extents.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Horizontal position of the survey aircraft used to collect data were determined by reconciling down-looking photographs (recorded on continuous-strip film) with topographic maps and orthophotoquadrangle maps. Fiducial numbers and marks, impressed on any paper strips that were recording data or added to magnetic tape records, were included as a function of time to further reconcile location with instrumentation
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
The aircraft vertical position was determined using the navigational positioning equipment on the aircraft, which were radar altimeter and barometric altimeter.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: Bromery, Randolph Wilson, Zandle, G.L.
Publication_Date: 1956
Title:
Aeromagnetic map of the Alton quadrangle, New Hampshire; Total intensity relative to arbitrary datum
Series_Information:
Series_Name: Geophysical Investigation Map
Issue_Identification: 136
Online_Linkage: http://pubs.usgs.gov/gp/0136/report.pdf
Type_of_Source_Media: paper
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 1956
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: paper
Source_Contribution:
Contours of magnetic anomaly and, where available, flight lines were digitized from this source
Source_Information:
Source_Citation:
Citation_Information:
Originator: Bromery, Randolph Wilson, Zandle, G.L.
Publication_Date: 1956
Title:
Aeromagnetic map of Berwick quadrangle, Maine and New Hampshire; Total intensity relative to arbitrary datum
Series_Information:
Series_Name: Geophysical Investigation Map
Issue_Identification: 137
Online_Linkage: http://pubs.usgs.gov/gp/0137/report.pdf
Type_of_Source_Media: paper
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 1956
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: paper
Source_Contribution:
Contours of magnetic anomaly and, where available, flight lines were digitized from this source
Process_Step:
Process_Description:
Aeromagnetic survey flown by USGS in the time period 09/55 direction E-W at altitude 750 AG with spacing 0.5 mi. for a total of 800 line miles
Process_Date: 195509
Process_Step:
Process_Description:
USGS digitized original paper map to ASCII format points. USGS personnel used the software package Oasis Montaj by Geosoft, Inc., to read in the ASCII digitized data and create raster JPEG images.
Process_Date: 2000 or later
