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:

  1. North
  2. 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:

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:

  1. Translation - which makes the (Local Reference) point match (UTM Reference) using the vector:
    (Local Reference) -> (UTM Reference)
  2. Rotation - The local system is rotated in (UTM Reference) from an angle formed by the vectors:    This value will be read-only if you choose to enter the local and UTM coordinates of the point of rotation.   
  3. 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: