Measuring Antenna Height at Measurement Mark

Antenna Model

Proper antenna models are required when processing observations collected with survey grade receivers. When selecting the appropriate antenna model, it is possible to reduce slant antenna heights (measured in the field) to vertical heights and to account correctly for antenna phase center vertical offset. This latter issue is particularly important when the user is seeking for centimeter level accuracy and is using antennas of different models at the base and the remote receiver.

 

For GIS users interested in horizontal components, all settings described in this articles are not important since they are used to get sub-centimeter accuracy in the height component. Moreover, if you are working at sub-meter level accuracy, this information isnít relevant.

 

In EZSurv, an antenna model is defined by a model name, a radius, a measurement mark offset and a vertical offset for L1 and L2 frequencies. The vertical offset for L2 will be zero if the antenna is single frequency. The radius is measured from the center to the edge of the antenna at the measurement mark (when measuring antenna height). The vertical carrier phase offset is the distance from the Antenna Reference Point (ARP) to the antenna phase center.

 

In this case, you need a Radius to reduce the slant to the vertical height and you need a Measurement Mark Offset in order to reduce the vertical height to the ARP. The model presented in this example has been imported from the NGS Table. Notice the * in the model name and the fact that we cannot edit the phase center offset. These characteristics are typical of NGS models. However, the Radius and the Measurement Mark Offset has to be entered by the user since these values are not provided by NGS. If the Measurement Mark is above the ARP, the Measurment Mark Offset value is negative, whereas a measurement mark below the ARP is positive. If required, users are invited to contact their equipment manufacturer to get accurate value for your antenna parameters.

 

When your models are created they can be associated to a specific site using the Site Editor (Edit > Site > Occupations tab) or the Rover Editor (Edit > Rover) for a kinematic file.

Antenna Parameters

Here are the different antenna parameters involved when measuring antenna height at a measurement mark (not to mix with the ARP). This is the typical case when you setup an antenna on a tripod.

Typically, all these measurements are described in an Antenna model like in this example:

Article: 000018

Related Products: EZSurv

Last Update: 2016-07-14 18:44:15

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