Ground control for 1:150,000 scale aerials, Greenland

Reference systems in Greenland

Triangulation
More than 6000 points have been surveyed in Greenland, mainly using terrestrial methods. At a few of these points, astronomical observations were made to locate the reference system in relation to the centre of the earth.


Mean sea level measurements
Elevation in Greenland has historically been determined from local observations of mean sea level. As a result, every town and settlement has its own local height datum. In total 200 to 300 measurements of varying quality and length were carried out. Tide was typical observed on rocks or rock walls from periods of a few hours to a couple of weeks. The longest series were measured in harbours.
Later, but still before GPS was introduced, the terrestrial net was supplemented with Doppler measurements using the satellite based navigation system Navy Navigation Satellite System (NNSS) also known as NAVSAT or TRANSIT.

Together with the Doppler measurements, the WGS72 system was introduced. This system was later replaced with NAD83g. In this context NAD83g is the same as NAD83(North American Datum 1983) and is the adaption of WGS84 in Greenland.


Definition of NAD83g
Topographic and cartographic works in Greenland in the years 1978 to 1987 required all ice-free parts of Greenland to be covered by aerial photographs in scale 1:150,000. An aerotriangulation using these photographs resulted in the extension of NAD83g to all parts of Greenland.


Definition of GR96
In the 1990s the need for a more accurate reference system in Greenland became evident through the common use of GPS. Thus the new reference system REFGR was established.  This reference network is measured using GPS and defines the official geodetic reference system in Greenland. GR96 is based on the global reference frame ITRF (International Terrestrial Reference Frame, ITF94). GR96 covers Greenland in its entirety.
In winter, 2006 all Doppler observations included in the first aerotrinagulation were recalculated, new were added and the aerotriangulation was recalculated, resulting in coordinates in the new datum GR96.

Coordinate lists for Greenland mapping projects

Coordinatelists in GR96 datum:

Coordinatelists in NAD83g datum:

Formats:
Coordinate list - Geographic in the format
Station Number, Latitude DDMMSS.SSSSS, Longitude DDMMSS.SSSSS, Altitude mmmm.mmm
Do not put too much emphasize on the fractions parts. Using only the integers make sense
Output Coordinate System: Geographical coord + MSL Heights
........Datum...........: World Geodetic System 1984
........Ellipsoide......: WGS84 or GR96

Coordinate list - UTM zone 22 in the format
Station Number, Northing m mmm mmm.mmm, Easting mmm mmm.mmm, Altitude m mmm.mmm
Do not put too much emphasize on the fractions parts. Using only the integers make sense

Output Coordinate System: UTM zone 22 coord + MSL Heights
........Datum...........: World Geodetic System 1984
........Ellipsoide......: WGS84 or GR96

Coordinate list - UTM zone 24 in the format
Station Number, Northing mmmmmmm.mmm, Easting mmmmmm.mmm, Altitude mmmm.mmm
Do not put too much emphasize on the fractions parts. Using only the integers make sense!

Output Coordinate System: UTM zone 24 coord + MSL Heights
........Datum...........: World Geodetic System 1984
........Ellipsoide......: WGS84 or GR96

 

Image coordinates for photostations (observations)

File containing all observations for the 1:150,000 scale imagery: All_photoobs.zip (download zipfile)

Camera calibrations

Download camera calibration documents as pdf files (700 - 900 kBytes each):
1978 - 1981 - 1985 and 1987 
NB! 1987 - error in camera constant (focal length) annotation - Read notification 

Match camera calibration fiducial mark numbers with observation file fiducial mark numbers:

 http://zajt.dk/coorweb/web_eks_lille.jpg

 

Guide lines for observation file

Inner orientation is defined by the physical location of fiducial marks 991 thru 998
relative to the lens cone identifyer (not to the annotation printed on the film).

If you place the camera with the lens cone ID to the left,
you will have Fiducial mark number
991 in the lower left corner
992 in the middle left
993 in the upper left
994 in the upper middle
995 in the upper right
996 in the middle right
997 in the lower right and
998 in the lower middle

Example of from the photo observation list

* Observations from kmsgeo 9. Aug. 2001, 14.22 page 1 ;

#GR_monoDacl xxx

P0874A0657 a 78 07 14 2035 0.087724 m
MFC 0.020 mm

M1601 81 06 25 AF
F991___-106.014 mm -106.002 mm
F992___-110.008 mm ___0.002 mm
F993___-106.001 mm _105.990 mm
F994_____-0.018 mm _109.982 mm

F995____105.972 mm _105.987 mm
F996____109.984 mm __-0.005 mm
F997____105.982 mm -105.993 mm
F998_____-0.012 mm -110.006 mm

F12614___42.570 mm __43.951 mm
F16034___86.754 mm __33.264 mm
F16035__107.101 mm __59.673 mm
F16036___74.630 mm __56.370 mm
F16037___98.163 mm __97.777 mm

F16038___26.991 mm __57.258 mm
F16039___47.007 mm __86.466 mm
F16040__-13.117 mm __68.947 mm
F16041__-11.088 mm _100.887 mm
F16042__-14.094 mm __58.109 mm

Disclaimer

Geodatastyrelsen cannot be held liable for any contents on this web site nor for any damage caused by its rightful or wrongful usage.

Historic coordinates used for map production prior to 2005-01-01

Coordinate list - Geographic in the format
Station Number, Latitude DDMMSS.SSSSS, Longitude DDMMSS.SSSSS, Altitude mmmm.mmm
Do not put too much emphasize on the fractions parts. Using only the integers make sense! Download zipfile
Output Coordinate System: Geographical coord + MSL Heights
........Datum...........: World Geodetic System 1984
........Ellipsoide......: WGS84

Coordinate list - UTM zone 22 in the format
Station Number, Northing m mmm mmm.mmm, Easting mmm mmm.mmm, Altitude m mmm.mmm
Do not put too much emphasize on the fractions parts. Using only the integers make sense! Download zipfile
Output Coordinate System: UTM zone 22 coord + MSL Heights
........Datum...........: World Geodetic System 1984
........Ellipsoide......: WGS84

Coordinate list - UTM zone 24 in the format
Station Number, Northing mmmmmmm.mmm, Easting mmmmmm.mmm, Altitude mmmm.mmm
Do not put too much emphasize on the fractions parts. Using only the integers make sense! Download zipfile
Output Coordinate System: UTM zone 24 coord + MSL Heights
........Datum...........: World Geodetic System 1984
........Ellipsoide......: WGS84

Each text file is about 1.5 mbytes (zipfile: 500 kbytes)