94

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

INSIGHT

Dear Mr. Nwamadi,

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

, 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

, 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

, 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

GeoBytes!

ASPRS GIS

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ivision

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nline

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eminars

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