No	Name	Flown By	Date Flown	Spacing	Dir	Altitude	LnMi	Datum	Publication
4041	Northeast Mt.-Western N.D.	Airmag	09/80	3 mi.	E-W	4000 B	6955	IGRF75, 59059	OF81-434
4042	South-central North Dakota	Airmag	09/80	3 mi.	E-W	3500 B	1730	IGRF75, 59028	OF81-433
4043	Raub	Airmag	09/80	3 mi.	E-W	3500 B	255	IGRF75, 59165	OF81-434
4251	NE North Dakota	Spectra	11/00-02/01	0.25 mi.	E-W	500 AG	18185	IGRF00	OF02-361

Description of Table

No.: Internal USGS identification number
Name: Internal project name (not always the name used in publication title)
Flown By: Company or government agency who flew the original survey
Spacing and Dir.: Primary flight-line spacing and primary flight-line direction
Altitude: Primary flight altitude in feet; B = barometric elevation, AG = above ground draped over topography
LnMi.: Approximate total of line miles flown for this survey
Datum: Indicates if a regional field was removed and, if it could be determined, the base value removed. Total field = no regional was removed. Arb. (arbitrary) datum = the base value removed was not stated on the map or in survey reports.
Publication: Brief publication reference*. USGS publications are listed as: Open-File reports = OFxx-yyyy where xx is the publication year, Bulletins and Professional Papers = B-yyyy or P-yyyy, Geophysical Maps = GP-yyyy, Miscellaneous Field Studies Maps = MF-yyyy, Miscellaneous Investigations Maps = I-yyyy.

*For a full reference for USGS publications see: http://library.usgs.gov/