Coordinates Systems

List of commands

Generalities

Presentation

Photogrammetry is often accompagned with a georeferencement (direct or indirect). The geographic position of targets or images is usually given in geographic system such WGS84 or RGF93 (France). To work with this coordinates in MicMac, yo have to transform it in a euclidian system. Best way is to work in a Local frame (RTL) define by the coordinates of one point of the field.

How to Use?

Two way to transform coordinates :

• With the tool ChgSysCo.
• With other tools such OriConvert or GCPConvert and the option ChSys.

For both case, you have to use the same syntax :

initial_coordinate_system@final_coordinate_system

For example, if you want to transform geographic to cartesian, you should use :

DegreeWGS84@GeoC

XML codage

Sometimes it's more easier to define the systeme in a file to use it several times.

• <SystemeCoord> : Define a system.
• <BSC> : BasicSystemeCoord.
• <TypeCoord> : Type of the coordinate (eTC_RTL,eTC_WGS84,etc...).
• <AuxR> : for a double.
• <AuxI> : for an integer.
• <AuxStr> : for a string.
• <AuxRUnite> : for unities.

Exemple :

<SystemeCoord>
   <BSC>
       <TypeCoord>eTC_RTL</TypeCoord>
          <AuxR>4320361.093</AuxR> #Center or RTL
          <AuxR>-98032.083</AuxR>
          <AuxR>4675380.773</AuxR>
   </BSC>
   <BSC>
      <TypeCoord>eTC_GeoCentr</TypeCoord> #Coordinate system of the center
   </BSC>
</SystemeCoord>

Implemented systems

Geocentric cartesian

• Directly on MicMac commands : GeoC.
• In file : eTC_GeoCentr.

WGS84 geographic

• Directly on MicMac commands : WGS84, or DegreeWGS84
• In file : eTC_WGS84.

RTL planes

For this system, you need to define it on a xml file with this structure :

<SystemeCoord>
   <BSC>
       <TypeCoord>eTC_RTL</TypeCoord>
          <AuxR>4320361.093</AuxR> #Center or RTL
          <AuxR>-98032.083</AuxR>
          <AuxR>4675380.773</AuxR>
   </BSC>
   <BSC>
      <TypeCoord>eTC_GeoCentr</TypeCoord> #Coordinate system of the center
   </BSC>
</SystemeCoord>

Polynomial

To do