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2.6 Settings Menu

2.6.1 GNSS Processing

This option gives access to most of the differential processing settings without allowing you to begin processing. Data processing can only be engaged via the Process button under Process | Process GNSS. See Section 2.5.1, on Page 61 for a complete description of all the settings available here.

2.6.2 PPP Processing

This option gives access to most of the PPP processing settings without allowing you to begin processing. Data processing can only be engaged via the Process button under Process | Process PPP. See Section 2.5.1, on Page 61 for a complete description of all the settings available here.

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2.6.3Coordinate

Master Station Settings

This option lets you modify the master station coordinates. See Section 2.3.6, on Page 36 for more information of the settings available.

Remote Settings

This option lets you customize the remote’s antenna information. See Section 2.3.7, on Page 37 for additional information.

Remote Initialization

In some cases, you may know the remote’s coordinates at a certain epoch or location from some other means, such as a previous survey or from another base station. It can be very helpful to seed, or even “fix”, the current trajectory using this known position.

One way to fix a position is to right-click on an object, for example an epoch, feature or static session, in the Map Window to bring up the Object Menu. With this menu, you can “fix” the remote position at any number of times or locations throughout the survey. This option works best with shorter baseline lengths and is intended primarily for surveyors. See Section 2.4.7, on Page 57 for more information on the Objects Menu.

Another way to “fix” a position is to use the

Manual Remote Initialization window. With it, baselines can be “fixed” on long baselines combined with dual frequency receivers. The options in this window includes the following:

When?

This options allows you to select or enter the times where the initialization takes place. This is a point of known latitude, longitude and height. It could be a station name (as it appears on the GrafNav screen) or a specific time.

For kinematic trajectories, selection of a time is preferable to the start/end method because the software may not start processing on the very first epoch. Be sure to set a small enough time window. For stations or static sessions, ensure that the antenna height is correct.

Select From Favorites

Allows you to easily find any pre-loaded station information. This feature searches through the Favorites Manager to find all stations within 5km of the input coordinates. This large search radius allows for the use of approximate coordinates as a search input. The window that appears lists all stations in order of proximity. When a station is chosen, the corresponding information is displayed in the Selected Station Information window on the right-hand side. Under the Attributes to copy, you can specify which information you wish to import to the project.

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Method for fixing position settings

Automatic

Selects one of the modes based upon baseline length, base/remote height difference and estimated accuracy of the current epoch.

Ambiguity Fix

Tends be the most robust method and does the best job of keeping the position selected, including any errors that might be present. Airborne applications should only use this method.

Snap to Integer

Practical for short baseline applications, like surveying. It selects the nearest integer position, which means that input position must be accurate to at least ½ cycle (10 cm for L1 and 40 cm for L1L2).

Position Fix

This works when the position's accuracy is suspect. Speeding up convergence does not always show that much improvement over not using a seed at all.

GLONASS requires the Ambiguity Fix method.

General Options

The following settings are available:

Direction

Defines processing direction in which the fix is to take place.

Method for fixing position

The different integer settings for this option are in the shaded box.

Advanced Options

The following settings are available:

Valid time window

In the When? section, select at which point the fix should be applied. This setting defines how close an epoch should be before it is used. For kinematic trajectories, this value should be half of the processing data rate.

In instances where there is a data gap, use this setting to define how close a time can be and still perform a fix.

Antenna height

Height of the antenna above the marker position entered below.

Standard deviation

Estimated accuracy of the position supplied. This is important for the Position Fix or the Automatic modes because they use it to decide which method of fix to use.

Position

This is the marker position that is used for all of the modes of position fix. This height plus the antenna height is the location to be used for the antenna position. See Section 2.3.6, on Page 36 for more details.

2.6.4 Individual

This option accesses the tabs in the process menu. See Process on Page 61 for more information.

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2.6.5Datum

These settings can also be accessing by the More Datum Options… button under Settings | Individual | General or through the Datum Manager, which has additional coordinate transformation capabilities. Section 9.10, on Page 285 offers more information on datums.

Project Options

Processing Datum

The datum selected here is the one that the data is processed in. This means that the software will convert the satellite coordinates into this datum. The easiest procedure is to select the local datum from the list of datums. If it is not available, then select the Datums tab and enable the datum. If the desired datum does not exist, then add a datum and a conversion. See Section 9.10, on Page 285 for more information.

WGS84 Processing datum conversion

This setting specifies the set of transformation parameters used to convert between datums. Enabling Automatic chooses the default datum conversion. A different datum conversion can be made the default by selecting the Datum Conversions tab. Otherwise, disabling Automatic allows you to select a datum conversion more appropriate for a given area. The accuracy of the datum conversion becomes more important with increasing baseline length. You can change the default conversion between datums with the Tools | Datum Manager.

Coordinate Input Datum

Use this setting to process in a more global datum, like WGS84, while entering the base coordinates in the local datum, like NAD27. The reasons to do this are listed in the shaded box.

To enter coordinates in a different datum than the processing datum, Convert input coordinates to processing datum must be enabled. In this case, the datum conversion becomes very important.

It important that the same conversion is used to transform the output back into that datum. Otherwise, a datum error of several meters may be induced on the final coordinates.

Reasons to use coordinate input datum

A grid style, like NADCON, conversion is used to transform between datums. Such a transformation does not convert satellites because they are often outside of the boundaries. See Section 9.10.5, on Page 287 for more information.

The datum conversion is heavily localized. This means that it may have very large rotation values and its transformation is only valid over a small area, like a city or state. Similar to NADCON, a you would not want to convert satellite coordinates using this transformation.

Currently, only the Export Wizard supports datum transformations. Be cautious with datum conversions, as their accuracy can always be suspect. See Section 9.10, on Page 285 for more information.

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Datums

This feature allows you to enable or disable datums. While there are over 100 datums in the list, only a few are enabled. This makes it easier to find a datum, because some are far more commonly used than others. New datums can also be added via the Add button. If a new datum is added, be sure to add a conversion as well.

Datum Conversions

This tab allows you to inspect, edit or add conversions between datums. Normally, conversions are from/to WGS84, although conversions between any two datums can be added. This tab can also be used to make a particular conversion the default conversion between a given datum pair. See Section 9.10, on Page 285 for more information.

Ellipsoids

This page allows you to inspect the a, b or 1/f values for a particular ellipsoid. You can also add new ellipsoids, although most of the world’s ellipsoids should already be present. See Section 9.10, on Page 285 for more information.

Grid / Map Projections

GrafNav projects store grid information. Set up a grid for the following reasons:

•Master coordinates can be entered directly in a grid system. This may be very convenient if data sheets do not give geographic coordinates.

•The Map Window can plot in grid coordinates. See Section 2.7.11, on Page 126 for more details.

•DXF output uses these grid settings. See

Section 2.7.12, on Page 127 for more information.

•Export Wizard can use a defined grid for coordinate output. See Section 2.7.4, on Page 111 for details.

New grid definitions can be added by clicking

Define Grid or via Tools | Grid/Map Projections | Define. See Section 2.8.7, on Page 133 for more information.

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