Calculate STP Elevation

Use the RPS > Calculate STP Elevation option (geogxnet.dll(Geosoft.GX.Radiometrics.CalculateSTPElevation;Run)*) to apply altimeter correction and calculate the STP Standard Temperature and Pressure equivalent elevation, adjusted for current temperature and pressure conditions. To generate the STP-corrected altitude output, the process requires input from either a barometric elevation or pressure channel, along with temperature and radar altimeter data. For further details, refer to the Application Notes.

Calculate STP Elevation dialog options

Method	Choose whether to correct the height using standard temperature and either barometric elevation or standard pressure: Barometric altitude channel: Select this option to correct using barometric elevation. Pressure channel: Select this option to correct using standard pressure. Refer to the Application Notes for the correction equations. Script Parameter: SPECTRO.STP_METHOD [0 - Barometric; 1 - Pressure]
Radar altitude channel	Select the radar altimeter channel. Script Parameter: SPECTRO.RALTRAW
Temperature channel (C)	Select the temperature channel. Script Parameter: SPECTRO.CTEMP
Barometric channel / Pressure channel (kPa)	This is a contextual parameter. Based on your Method selection, either the Barometric channel or the Pressure channel field will be enabled. Script Parameters: SPECTRO.BALTRAW SPECTRO.PRESSURE
Low-pass cutoff (fiducials)	Before converting to equivalent height at standard temperature and pressure (STP), you may need to apply light filtering to your radar altimeter data to smooth out abrupt terrain changes. Enter the cutoff value to apply filtering. Default: 5 Enter 0 to skip filtering. Script Parameter: SPECTRO.RALTSWAV
Output STP altitude channel	Specify the output channel for the STP-corrected altitude. Default name: RALTSTP Script Parameter: SPECTRO.RALTSTP

Application Notes

STP Correction Equations

To apply radiometric analysis techniques, actual survey conditions must be converted to standard conditions. This involves adjusting the measured ground clearance to standard temperature and pressure (STP). The resulting "equivalent height" represents the same mass of STP air between the ground and the aircraft as was present during data acquisition.

The STP-corrected altitude can be calculated in two ways, depending on available channels:

Correction for Standard Temperature and Pressure

• Standard temperature: 273.15 K

• Standard pressure: 101.325 kPa (equivalent to 101325 Pa or 1 Atm)

To correct the height for standard temperature and pressure, the formula is:

Correction for Standard Temperature and Barometric Elevation

The calculation above assumes the availability of radar altimeter, temperature, and air pressure data. However, some systems may not provide direct pressure measurements. In such cases, barometric altimeter readings can be used.

To correct the height for standard temperature and barometric elevation, the formula is:

Processing Workflow

This RPS tool performs two processes:

1. Low-pass filtering of radar altimeter data

2. STP correction of altitude

After processing:

• Compare raw and corrected data in the profile window.

• If results are unsatisfactory, rerun the GX and adjust parameters as needed.

References