# factorGPS

Factor for GPS measurement

## Description

The `factorGPS` object adds a constraint to a node in a `factorGraph` by using a GPS position measurement.

## Creation

### Syntax

``F = factorGPS(NodeID)``
``F = factorGPS(NodeID,Name=Value)``

### Description

````F = factorGPS(NodeID)` returns a `factorGPS` object, `F`, with the node identification number set to `NodeID`. The GPS factor adds a constraint to the corresponding factor graph node by using a GPS position measurement.```

example

````F = factorGPS(NodeID,Name=Value)` specifies properties using one or more name-value arguments. For example, `factorGPS(1,VDOP=1)` sets the `VDOP` property of the `factorGPS` object to `1`.```

## Properties

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Node ID number, specified as a nonnegative integer. The GPS factor connects to this node in the factor graph.

You must specify this property at object creation.

Geodetic position measurement, specified as a three-element row vector of geodetic coordinates in the form (`latitude` `longitude` `altitude`). Latitude and longitude are in degrees and altitude is in meters.

Horizontal dilution of precision, specified as a positive scalar.

Vertical dilution of precision, specified as a positive scalar.

Origin of the local coordinate system, specified as a three-element row vector of geodetic coordinates in the form (`latitude` `longitude` `altitude`). Latitude and longitude are in degrees and altitude is in meters.

Altitude is the height above the reference ellipsoid mode, WGS84.

Reference frame for the local coordinate system as `"ENU"` (east-north-up) or `"NED"` (north-east-down)

## Object Functions

 `nodeType` Get node type of node in factor graph

## Examples

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Set up parameters such as the connected node ID, and reference location. Then create a GPS factor with these parameters as arguments, and set the reference frame to "`NED"`.

```id = 1; loc = [5 5 1000]; hdop = 1.5; vdop = 2.4; refloc = [0 0 100]; f = factorGPS(id,Location=loc,HDOP=hdop,VDOP=vdop,ReferenceLocation=refloc,ReferenceFrame="NED");```

Create a default factor graph and add the factor to the graph using the `addFactor` function.

```g = factorGraph; addFactor(g,f);```

## Version History

Introduced in R2022a