Choice of Zone, meridian and hemisphere
When using the TBN2CAD programs, you need to tell which Zone, Meridiano Central and which hemisphere
Refers to the UTM coordinate system. It is known that the Globe is divided into 2 hemispheres by the Equator:
 North
 South
In the vertical, the Globe is divided into 60 Zones, each with its Central Meridian, the Greenwich Meridian being the number zero:
Sometimes it is difficult to identify the Zone in which the drawing is in AutoCAD, so to facilitate,
The program shows this screen to click on the approximate region from where the drawing should "drop":
Click and drag the marker to the position of your project.
Note that in this screen you should still choose the drawing reference, which can be, for example, SAD69. Thus the coordinates will be correctly transformed
Because Google Maps and Bing Maps are in the WGS84 framework.
Transforming Local Coordinates to UTM
Finally, you can still choose to turn the UTM coordinates into local coordinates. To do this, check the box Applies Transformation and define the parameters:
 Report Rotation  choose whether you want to report the rotation of your coordinate system at the reference point defined below, bypassing the local coordinates
UTM of the point of rotation. By choosing this option, enter an angle in decimal degrees, counterclockwise from the
North.
If you choose to enter the point of rotation, you must enter the local and UTM coordinates of the point of rotation, so the angle will be
Calculated

Reference  is the source of your coordinate system
 Local Coordinate
 X  corresponds to abscissa, in meters
 Y  corresponds to ordinate, in meters
 UTM Coordinate
 N  corresponds to ordinate north
 E  corresponds to east abscissa

Rotation  indicates the rotation of your coordinate system
 Local Coordinate
 X  corresponds to abscissa, in meters
 Y  corresponds to ordinate, in meters
 UTM Coordinate
 N  corresponds to ordinate north
 E  corresponds to east abscissa
Note that by filling in the above values, the scale factor (K) and system rotation will be automatically calculated.
Local coordinates transformation to UTM consists of:
 Translation  which makes the (Local Reference) point match (UTM Reference) using the vector:
(Local Reference) > (UTM Reference)
 Rotation  The local system is rotated in (UTM Reference) from an angle formed by the vectors:
 (Local Reference) > (Local Rotation)
 (UTM Reference) > (UTM Rotation)
This value will be readonly if you choose to enter the local and UTM coordinates of the point of rotation.
 Scale  using the point (UTM Reference), the coordinates are scaled using the factor K, given by the formula:
K = k0 / (1  (Cos (LAT)) * Sen (LNG averaged  LNG)) 2) ^ 0.5
LAT + = If (LAT <0, 1, 1) * Truncate (Abs (LAT) / 8) * 8 + 4
LNGmedio = Zone * 6  183
where:
 k0 = scale factor = 1  1/2500 = 0.9996
 Cos , cosine function
 Sen , sine function
 Truncate , function that returns the integer part of a number
 Abs , function that returns the absolute value (module)
 LATmedio , mean latitude for the reference point.
 LNGmedio , average length for the reference point.
 LAT , landmark point latitude
 LNG , reference point length
 Zone , Zone, or system zone