Navigation Correction

Use the Navigation Correction option (Geosoft.uxo.gxnet.dll(Geosoft.GX.UXO.UceNavCorr;Run)*) to correct for navigational errors.

ClosedExpand to see the locations (menus) where this option is available.

UXO Land extension:

  • Data Preparation > Path Corrections

UXO Marine extension:

  • UXO-Marine Grad > Path Corrections
  • UXO-Marine Mag > Path Corrections

Navigation Correction dialog options

Database

Name

Select the name of the database to process.

Script Parameter: UCENAVCORR.GDB

Lines to correct

Select the database lines to be corrected.

Script Parameter: UCENAVCORR.LINES

X backup channel

Specify the name of the X backup channel (original X channel).

Script Parameter: UCENAVCORR.XBACK

Y backup channel

Specify the name of the Y backup channel (original Y channel).

Script Parameter: UCENAVCORR.YBACK

Reset current X/Y with backups

Select this option to reset the current X/Y channels with the backup channels defined above. If this is not selected the current X/Y channels will be used.

This option is not selected by default.

Script Parameter: UCENAVCORR.RESET_XY

Output Map

Output map name

Specify the name of the output map.

Script Parameter: UCENAVCORR.MAP

Orig/corr line path thickness (mm)

Specify the original and corrected line path thickness, in millimetres.

Script Parameter: UCENAVCORR.LINEPATHTHICK

Orig/corr symbol size (mm)

Specify the original and corrected symbol size, in millimetres.

Script Parameter: UCENAVCORR.SYMBOLSIZE

Current (corrected) line thickness (mm)

Specify the current (corrected) line thickness, in millimetres.

Script Parameter: UCENAVCORR.LINETHICK

Position quality symbol size (mm)

Specify the position quality symbol size, in millimetres.

To enable this parameter you must first select a Quality flag channel, in the Automatic position correction options section of this dialog.

The position quality symbol legend will be plotted on your map.

Script Parameter: UCENAVCORR.QUALITYSYMBOLSIZE

Keep individual corrected line map groups

Select this option and the individually corrected (manually corrected) line map groups will be saved to your map and displayed in the View/Group Manager Tool. The names of the individually corrected line map groups are derived from the database line name.

Script Parameter: UCENAVCORR.KEEP_GROUPS

Automatic Position Correction

Correct for zero position

Select to correct navigation readings that are zeros.

Script Parameter: UCENAVCORR.CORRPOSZERO

Correct for positional double hits

Select to correct the repeated navigation readings with a linear extrapolation (or just dummy out) between previous and next valid readings.

Script Parameter: UCENAVCORR.CORRPOSREP

Time channel

Select the name of the channel containing the time stamps, required for time double hits correction. If this field is blank, no time correction is done.

Script Parameter: UCENAVCORR.TIMECH

Quality flag channel

Select the name of the fix quality channel, required for the fixed quality correction of the navigation data. If this field is blank, no fixed quality correction is done.

Script Parameter: UCENAVCORR.FQCH

Min. acceptable quality

Specify the threshold flag below which to correct the navigation data.

If left blank, it will be set to the min value of the Fix quality channel.

Script Parameter: UCENAVCORR.FQMIN

Max. acceptable quality

Specify the threshold flag above which to correct the navigation data.

If left blank, it will be set to the max value of the Fix quality channel.

Script Parameter: UCENAVCORR.FQMAX

Fill corrected points

Select to interpolate or dummy out (don’t move over the corrected points):

Interpolate: 1

Dummy out: 0

Script Parameter: UCENAVCORR.REPLACEPTSAUTO

Manual Position Correction

Correction for jumps?

Select to manually select the segments to be corrected, while in interactive mode:

Straight line: 2
Poly line: 1
No correction: 0

Script Parameter: UCENAVCORR.CORRJUMP

Fill corrected points

Select to interpolate or dummy out (don’t move over the corrected points):

Interpolate: 1

Dummy out: 0

Script Parameter: UCENAVCORR.REPLACEPTS

Application Notes

We acknowledge the co-operation of Geo-Centers in the development of this navigation correction tool. Geo-Centers have contributed its numerous years of field experience by sharing with Geosoft the methodology implemented in this tool.

The Path correction tool was developed to correct GPS navigational errors. GPS uses an array of up 28 orbiting satellites to locate positions on the Earth's surface. To provide precise coordinates in 3 dimensions a minimum of 4 satellites are required. The satellite signals are received on the ground by a receiver unit that calculates the time delay of the signal to calculate a distance from the satellite; with the distances from all available satellites a fix of position is possible. While GPS can be an extremely precise mode of surveying, there are potential errors that if left uncorrected can compromise the accuracy of the data. GPS data may contain jumps, dog-legs, and shifts that will place sensor data at the wrong coordinates.

With this navigation correction tool you can automatically correct for:

  • zero positions (no data being collected),
  • positional double hits (repeated position readings),
  • time double hits (repeated time stamps),
  • quality of position data (quality of the position based on satellite signals, positional dilution of precision (PDOP) or some other indicator).

and manually correct for:

  • data jumps (radio signals from transponders multipath or suffer interference from cultural radar sources).

These corrections can be applied to all survey lines or only user selected lines. The original X,Y coordinate channels are renamed and saved as a backup within the database.

The fix quality of position data are saved in a new channel (quality_corr) in the database, in which the new flag will be set to -1 if the original fix quality value is not in the acceptable min/max range).

Navigation Manual Correction Instruction

In interactive mode users can manually select polyline or straight line points to be corrected. Exact number of "from" and "to" points for polyline must be selected for each line, while only have to pick the start and end points for straight line correction. The following directions are provided on a popup message:

Polyline correction:

  1.          Pick original points to be moved (right mouse click and press done when finished).
  2.          Pick new locations for the original points (right mouse click and press done when finished).
  3.          Select another section/line for correction, or hit Esc to finish.

Straight line correction:

  1.          Pick start/end points of a segment to straighten (right mouse click and press done when finished).
  2.          Select another section/line for correction, or hit Esc to finish.

*The GX tool will search in the "gx" folder. The GX.Net tools, however, are embedded in the Geosoft.uxo.gxnet.dll located in the bin folder. If running this GX interactively, bypassing the menu, first change the folder to point to the bin folder, then supply the GX.Net tool in the specified format.