# Position
{% hint style="info" %}
The following tabs are only enabled if the “Configure Reference Station (Position/Output)” checkbox is selected:
{% endhint %}
The position and height of the reference station is extremely important and must be properly configured. The rover depends on various height parameters, including ellipsoidal, geoid, orthometric, MSL (mean sea level), and reference station height to generate accurate data. If any of these parameters are incorrect, there is no way to generate correctly georeferenced point clouds.
\
The elevation above the ellipsoid (ellipsoidal height) is the elevation above a mathematical model that approximates the shape of the earth. The current most common one is WGS84. These are the elevations that you'd get from a GPS. Our points measure WGS84 ellipsoidal height in meters. If you wish to convert the points to another geodetic datum, we offer a tutorial video, [How to apply geoid heights using LAStools](https://www.phoenixlidar.com/tutorials/), on our homepage.
## Average Position
This tab will configure the reference station to measure its own position for a preset amount of time if accurate georeferencing is not required or is not possible. It will accept the average of those measurements as its own position. The position will only be accurate to the submeter after a few hours of averaging, therefore the produced map will not be accurately georeferenced. Furthermore, the reference station will not emit differential corrections before it has finished averaging measurements.
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| ----------------------------------------------------- | -------------------------------------------------------------------------------------------- |
| The reference station will determine its own position | Enabling this button will configure the reference station to calculate its Average Position. |
| Maximum Time | Maximum amount of time for reference station to determine its location. |
| Maximum Standard Deviation (Horizontal) | Maximum variation in horizontal distance with respect to the reference station’s location. |
| Maximum Standard Deviation (Vertical) | Maximum variation in vertical distance with respect to the reference station’s location. |
## Known Position
This tab will configure the reference station’s position, more specifically the position of the antenna phase center, over a known, precise point in WGS84 datum. GPS uses a height system that measures height from the WGS84 ellipsoid model of the earth.
{% hint style="info" %}
SpatialLightHouse uses nine decimal places to measure both Latitude and Longitude. You may have coordinates with greater than nine decimal places, however we have determined that nine decimal places allows for more precision than is necessary. Each decimal place provides precision relative to accuracy. As a general principle, you don't need much more precision in recording your measurements than there is accuracy built into them. For example, one decimal place can estimate accuracy up to a range of 11.1 km, roughly the position of one large city from its neighboring large city. Five decimal places can estimate accuracy up to 1.1 meters. It is important to note that accuracy to this level with commercial GPS units can only be achieved with differential corrections. In contrast, nine decimal places can estimate accuracy up to a range of 110 microns. For almost any conceivable application dealing with position on Earth, this provides more precision than the accuracy of any surveying device. Including 10 or more decimal places is useless and unnecessary for our accuracy purposes.
{% endhint %}
| | |
| ------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------- |
| Latitude/Longitude | The coordinates can be entered in various formats:
- Degrees
- Degrees, Minutes
- Degrees, Minutes, Seconds
|
| Edit | Access reference station height configuration interface. |
| Height of L1 phase center | The combined height of the reference station when measured from the surface of the WGS84 ellipsoid to the L1 phase center. |
### Reference Station Height
This interface will help you calculate the height of the reference station when measured from the surface of the WGS84 ellipsoid to the L1 phase center. This measurement is a summation of three separate height calculations.
```
Applied Height = (H. of Marker above WGS84 Ellipsoid) + (H. of ARP above Marker) + (H. of L1 Phase Center above ARP)
```
| | |
| -------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Antenna Type | A list of the different models of reference stations. Selecting an antenna will configure the “Height of L1 Phase Center above ARP” corresponding to that antenna. |
| Height of L1 Phase Center above ARP | The distance from the base of the reference station to the L1 phase center. |
| Height of Antenna ARP above Marker | The distance from the marker to the bottom of the base of the reference station. |
| Height of Marker above WGS84 Ellipsoid | The distance from the surface of the WGS84 ellipsoid to the marker. |
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