Ann: Loma Bonita Delivers More High Grade Gold-AZS.AX, page-52

Thank you for your enquiry.

At Azure we use NAD27 Mexico datum because it is the most accurate grid system for this region.

Google Earth uses WGS84 which is similar (but not equal) to NAD83. (NAD83 and WGS84 are typically within one meter of each other.) The discrepancies you have described are a result of using the NAD27 Mexico collar coordinates in Google Earth’s WGS84 coordinate system.

NAD27 is for the continental US and NAD27 Mexico is a slight variation on that. They are close but not equal. (At Alacrán the difference in easting and northing between NAD27 Mexico and NAD27 US is approximately +6.7mE and -3.1mN).

You have asked for a “grid conversion factor”. At Alacrán, NAD27 Mexico coordinates can be changed to UTM WGS84 by subtracting 57.8m from the easting and adding 197.4m to the northing.

I hope this answers your query and you can post this reply on Hot Copper.

Best Regards,

Tony Rovira
Managing Director