UTM 27 for a Zambian countrywide projection

[Oliver_Burdekin]

I'm working on some data from Zambia and some surveyors reports and data have come back with the odd projection of UTM 27. UTM 27 in the standard UTM system would be used for data in the middle of the Atlantic. Zambia looks like UTM 35S would be more suitable.

On further investigation I found this Masters Thesis which states:

"The common practice, in GIS, of using UTM system with longitude 27o east as central meridian for country-wide mapping is not supported by any scientific study with regards to the inherent errors and possible corrections."

This would explain where the UTM 27 reference is coming from.

Would using Arc50 UTM35S and modifying the central meridian property be a way to achieve this projection or does anyone know where I can find a complete specification?

[DanPatterson_Retired]

Melita Kennedy‌ would be the expert in that regard

[MelitaKennedy · Accepted solution]

The big question is whether they used the other UTM parameters, in particular the scale factor = 0.9996 or instead used parameters like those in the South Africa Lo system, which was every 3 degrees. The scale factor is 1.0, and the false easting/northing values were zeroes. If it looks like the false easting/northing values match a South UTM zone (false easting = 500km; false northing = 10000km), use the UTM 35S.

Melita

[Oliver_Burdekin]

Thanks Melita,

Further reading of the masters thesis I came to same conclusion. It is proving quite difficult to find further information other than that thesis. Always interesting to learn more about odd coordinate systems and thanks for getting back to me.

Cheers,

Oliver

[KaneShenton]

Thanks for your answer Melita. As I'm completely new to these questions, I was wondering if you could help converting one to the other. So for example, I have a coordinate in the Zambian 'UTM 27' system that is:

Easting:  663386.15

Northing: 8293522.83

And that is roughly:

Easting: 663385.03

Northing: 8293227.69

in the standard UTM, zone 35L.

Is that enough info to figure out how to convert from one to another? 

Many thanks,

Kane