Localization in MAGNET Field

When performing a task of transformation of GNSS points coordinates measured in WGS-84/Datum/Grid coordinate system into a Ground coordinate system, we cannot use the algorithms of transformation which are applied to predefined or created by the user grids and datums. In this case, MAGNET Field does not have predefined relation between two coordinate systems. We use Localization to perform coordinate transformation from WGS-84/Datum/Grid to Ground (and vice versa).

Related topics:



Basic Concept of Localization

Localization in MAGNET Field is a calculation of transformation parameters between WGS84/Datum/Grid and a ground coordinate system. To perform localization, you need to have two independent sets of coordinates for the same point or few points in the MAGNET Field. An independent set of coordinates is a set of such point coordinates that do not have a relation between each other. To perform localization in MAGNET Field, you need to manually select coordinates in the Ground coordinate system ("Known Point") and in the Grid coordinate system or WGS84/Datum coordinate system ("Measured Point") for the same point in the current job. Such a point is called Localization Point.

In MAGNET Field, horizontal localization and vertical localization are performed separately.

You determine how the localization points will use in localization parameters calculation by selecting the corresponding check boxes:

Also you can select the point which will use only in the determination of rotation between two coordinate systems by selecting the corresponding check box Rotation Only.

When you check Use Horizontal and / or Use Vertical you can use one, two, three and more localization points. For this case MAGNET Field will calculate a different set of transformation parameters and residuals. The table displays which parameters are calculated in the process of localization, some parameters can be set to zero depending on the used number of the localization points:

In the horizontal plane:

PARAMETERS

ONE

Point

TWO

Points

THREE

Points

FOUR

Points

DX,DY- horizontal offset between two coordinate systems CALC CALC CALC CALC
Scale - combined Scale factor CALC CALC CALC CALC
Rotation - rotation between two coordinate systems 0 CALC CALC CALC
N Residual, E Residual - residuals on the horizontal plane 0 0 CALC CALC

In the vertical plane:

PARAMETERS

ONE

Point

TWO

Points

THREE

Points

FOUR

Points

H0 - vertical offset between two coordinate systems CALC CALC CALC CALC
Deflection North, Deflection East- Deflection components 0 0 CALC CALC
Ht Residual - residuals on the vertical plane 0 CALC 0 CALC

When you check Rotation Only for a localization point, you need add to localization one or more localization points with Use Horizontal or Use Horizontal and Use Vertical status. For this case MAGNET Field will calculate:

If a geoid model is set in the job, MAGNET Field will use this geoid model for calculating orthometric height (elevation).

The current version of MAGNET Field enables you to perform the horizontal localization in three ways:

  1. Using default (the stereographic) projection on WGS84 (Find out more...).
  2. Using default (the stereographic) projection on any datum (Find out more...).
  3. Using any predefined or created projection (Find out more...).


Localization

In the dialog you can select the type of localization and see the points are used in the calculation of the transformation parameters.

  1. Select the Type of Localization. You can see the following types:
  2. Click Add to open the Add Localization Point dialog for adding control point(s). The quantity of points required for localization depends on how these points are used in localization parameters calculation.
  3. Note: The localization is recomputed every time a new point is added to the list of localization points. The new coordinate system will be saved under the name "Localization" and is automatically selected in the Coordinate System dialog.

  4. Select the Keep scale 1.0 check box to preserve the localization from a scale transformation as required. If this parameter is not selected (default settings), the scale factor will be calculated according to the number of localization points.
  5. If needed, click Edit to open the Edit H/V Controls dialog to change how these points are used in localization parameters calculation.
  6. Click Remove to remove the highlighted points pair(s).
  7. Click Details to view the results of the localization.
  8. Click to apply changes and exit the Localization dialog.
  9. Note: In specific cases, clicking you can receive a message that reads "Please check pair X". In such a case, the following actions are required:
    1. Select the pair in the list of point pairs in the Localization dialog.
    2. Click Edit.
    3. Click . You will get a message that contains problem description and recommended solution.

The icon opens a pop-up menu in which you can select additional features of localization More...

Related topic:



Pop-up menu of Localization

The pop-up menu contains a set of the following options:



Add Localization Point / Edit H/V Controls

In the dialog you can add known point and measured point to localization or to edit localization controls of existing localization point.

  1. Select the localization control where the point will be used:
  2. In the Known Point field, enter the Point in the local (ground) coordinate system. You can enter the point manually or select it from the map or from the list of the job points.
  3. In the Measured Point field, enter the Point in the coordinate system that is set for the current job. You can enter the point manually, select it from the map or from the list of the job points. For the GNSS device type, you can also measure the point coordinates by clicking .


    In the measure point coordinates dialog:

  4. Click to save the point and return to the Localization dialog with a newly added point.


The icon opens a pop-up menu which contains a set of the following options:



Localization Details

The Localization details dialog displays the input and calculated parameters of the localization:


The Map tab displays all points of the project. Localization points are marked by blue triangles showing how this point is used in current localization: