# PE&RS February 2015 - page 94

94
February 2015
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
by European instrument factories to
the now current softcopy systems.
The development of computational
photogrammetry started with curve-
fitting spline functions and progressed
significantly after the development of
digital computers. The collinearity
equation functioned well with
calibrated
cartographic
mapping
cameras, but eventually other models
had to be developed to accommodate
non-metric cameras. The reprint of
the Direct Linear Transformation
(DLT) was one of the novel approaches
developed by Abdel-Aziz & Karara.
The latest math model common in
use with satellite-based non-metric
sensors is now the rational function.
Clifford J. Mugnier, C.P., C.M.S.,
FASPRS
Louisiana State University
INDUSTRY
INSIGHT
Letter to the Editor—Grids & Datums
Good day sir, my name is Arthur Nwamadi I encountered a type of coordinate
system known as the Colony Coordinate System during my research on it led me
to a paper published by ASPRS, but I haven’t make a head way with it. I kindly
ask for your assistance concerning the conversion of this Colony Coordinate System
to a more recent one like the UTM or D.M.S. An example of the coordinates are
N 1,073,260 E 1,881,990 and it’s a location somewhere in Nigeria. Please your
assistance will highly be acknowledged.
The 1920 Nigerian Colony Coordinates have three zones: West, Central, and East.
With just the Grid coordinates, it is impossible to determine which Zone is being
used to perform the transformation. Therefore, I have done transformations for all
three zones:
=====================================
For Colony Coordinates
West Zone
, Minna Datum:
Note that the Central Meridian (λ
o
) = 4°30´ E
Note that the False Easting = 757,022.100
N = 1,073,260
E = 1,881,990
φ = 6° 56´ 56.3978˝ N
λ = 7° 36´ 07.5097˝ E
======================================
For Colony Coordinates
Central Zone
, Minna Datum:
Note that the Central Meridian (λ
o
) = 8°30´ E
Note that the False Easting = 2,200,000
N = 1,073,260
E = 1,881,990
φ = 6° 57´ 30.0665˝ N
λ = 7° 37´ 21.6776˝ E
=======================================
For Colony Coordinates
East Zone
, Minna Datum:
Note that the Central Meridian (λ
o
) = 12°30´ E
Note that the False Easting = 3,642,977.900
N = 1,073,260
E = 1,881,990
φ = 6° 56´ 03.4770 N
λ = 7° 38´ 51.3830˝ E
=======================================
All transformations were checked for both direct and inverse
and each agreed within 3 millimeters (with original equations)
using software that I have written myself.
Best regards,
Clifford J. Mugnier, C.P., C.M.S.
Louisiana State University
Letter From Clifford J. Mugnier
GeoBytes!
ASPRS GIS
D
ivision
— F
ree
O
nline
S
eminars
The ASPRS GIS Division,
in cooperation with CaGIS