AEROMAGNETIC DATA

National Coverage - Overview

The entire data set is available as a 200 m grid which is updated annually to reflect recent data acquisition.

Map Index 2

The entire aeromagnetic coverage of Canada is being levelled to one common datum. This will result in a "seamless" grid of contiguous aeromagnetic surveys from coast to coast, irrespective of the year flown, altitude, or type of survey. Levelling started with Ontario and the Atlantic provinces and that initial grid is being extended west and north. (Map Index 2 shows the national aeromagnetic coverage, levelled to one common datum.)

The Canadian Aeromagnetic Data Base consists of data from the following sources:

Digitized from Contour Maps

These data were collected before the advent of digital recording. The original 1:63360 or 1:50 000 contour maps have been digitized. Typical line spacing was half mile(805m) and altitude, 1000 feet (305m) above ground.

These data were acquired between 1947 and the late 1970's and recorded in analogue form. Originally, the magnetic readings from analogue surveys were manually transcribed onto flight path maps and hand contoured at a scale of 1:63 360 and 1:50 000. Digital profile records were later created by locating the intercept of each contour interval (typically 10 nT intervals) along flight path lines. Typical line spacing was half mile (805m) and altitude 1000 feet (305m) above ground.

The profile records contain:

• line header indicating the year of the survey and the flight altitude
• data records consisting of latitude, longitude, magnetic value for each digitized point.

Prices for Digitized Data

(based on a 15' x 30' map sheet)

Profile data: Latitude, longitude, magnetic value

• $8 per sheet

Grid data: magnetic values

Digitally acquired data

Map Index 3

Regional surveys
Line spacing typically 800m but can range up to 2, 4, and 6 km; flying was done at either constant barometric altitude (BAR) or mean terrain clearance (MTC).

Detail surveys
Typical line spacing of 300m and flight altitude of 150m mean terrain clearance(MTC).

Regional surveys

These data encompass reconnaissance surveys that have been flown from the 1970's to present. Line spacing ranges from 800m to 2, 4, and 6 km, and the surveys were flown at a constant barometric altitude or in some instances, mean terrain clearance. Recorded parameters typically include: total field magnetics, radar and barometric altimetry, navigation information.

Detail surveys

These are target specific surveys with 300m being the typical line spacing and 150m mean terrain clearance (MTC) the flying height. Recorded parameters include some or all of the following: total field magnetics, radar and barometric altimetry, navigation information, vertical gradient magnetics, VLF-EM, several EM channels.

Survey parameters and location of individual projects are listed in Appendix A.

Prices for Digital Data

(based on line kilometres)

Profile data:

1.	Latitude, longitude, magnetic value	$0.01/line km
2.	Latitude, longitude, magnetic values, radar, barometric altitude, plus where recorded: electronic navigation, VLF-EM, vertical gradient magnetics	$0.03/line km

Grid data: magnetic values

Offshore and Marine Coverage

Map Index 4a

Arctic and North Atlantic Oceans
and adjacent land areas

This data set was released by GSC Atlantic in 1996 under GSC Open File 3125. The project acquired and merged data sets from numerous organizations into a 5-km grid. (This replaces Open File 1504.)

The data and maps are distributed by GSC Atlantic. Visit the following web pages for more information, or to download.

Open File Number:
3125a:  CD-ROM only (5-km grid, ancillary files, Report in digital form).	$250
3125b:  Project Report only (in hardcopy form).	$250
3280, 3281, 3691:  Related maps.	$15/map

Map Index 4b

Hudson Bay

Data from shipborne surveys (1975 to 1978) were compiled as one data set and released in 1982. The sensor was towed 200 m behind the ship; corrections were applied to compensate for geomagnetic field disturbances.

Combined marine and aeromagnetic observations are available as part of the national 2 km grid.

$0.01/line km

West coast

Shipborne data (1973-1985) extending from the Strait of Juan de Fuca to Queen Charlotte Islands and westward 200 nautical miles are available as track records.

The national 2 km grid incorporates other data and extends further westward.

$0.01/line km

International Coverage

The Canadian International Development Agency (CIDA) has sponsored analogue and digital aeromagnetic surveys in several countries. In certain cases the digital data are stored at the GDC, while in other instances the host country holds these records. Often the permission of the host country is required before the data can be released.

The following table provides basic information about each survey, and whether or not the digital data are available from the Geophysical Data Centre.

List of International Aeromagnetic Surveys