The Tunisia Mining Grid has been implemented following the formulas outlined by the International Association of Oil & Gas Producers in IOGP Publication 373-7-2: Geomatics Guidance Note number 7, part 2, which states:
"This grid is used as the basis for mineral leasing in Tunisia. Lease areas are approximately 2 x 2 km or 400 hectares. The corners of these blocks are defined through a six figure grid reference where the first three digits are an easting in kilometres and the last three digits are a northing. The latitudes and longitudes for block corners at 2 km intervals are tabulated in a mining decree dated 1st January 1953. From this tabulation in which geographic coordinates are given to 5 decimal places it can be seen that:
- the minimum easting is 94 km, on which the longitude is 5.68989 grads east of Paris.
- the maximum easting is 490 km, on which the longitude is 10.51515 grads east of Paris.
- each 2 km grid easting interval equals 0.02437 grads.
- the minimum northing is 40 km, on which the latitude is 33.39 grads.
- the maximum northing is 860 km, on which the latitude is 41.6039 grads.
- between 40 km N and 360 km N, each 2 km grid northing interval equals 0.02004 grads.
- between 360 km N and 860 km N, each 2 km grid northing interval equals 0.02003 grads.
This grid could be considered to be two equidistant cylindrical projection zones, north and south of the 360 km northing line. However this would require the introduction of two spheres of unique dimensions. IOGP has therefore implemented the Tunisia mining grid as a coordinate conversion method in its own right."
Within the Geographic Calculator, the "Tunisia Mining Grid" projection does not specify any parameters, nor does it use the ellipsoid of the underlying geodetic coordinate system.