Steps for performing an Airfield Site Survey
1. The RPI or Runway Point Of Intercept is the point where
the aircraft wheels will physically touch the runway should the aircraft cross
the landing threshold at the prescribed Threshold Crossing Height (TCH)
expressed in whole feet; while maintaining the prescribed Glide Slope (GS)
expressed in degrees and tenths of degrees.
The formula for this is depicted on the slide.
2. The result of the calculation for RPI will yield a number
that is expressed in whole feet.
This measurement is the Distance to Threshold or
(DTHR).
The DTHR is used to measure from the landing threshold along
runway centerline to indicate the location of RPI; a marker is then placed at
the point of measurement.
3. The Azimuth Angle from Radar to RPI is known as the (AZRP).
The AZRP is expressed in degrees and
tenths of degrees. Because the RPI is our
point of origin; AZRP will always be Zero.
4. The Azimuth Angle from Radar to Centerline is the (AZRC).
It is the angle of difference in degrees and tenth of degrees from the RPI to
the Proposed Radar site…This angle can be no greater than 11 degrees.
5. The Elevation Angle Point of Intercept known as (ELRP) is
the difference displayed in degrees and tenths of degrees between the elevation
at the proposed radar site and RPI. This measurement is obtained by first marking the height of
the theodolite at the proposed radar site on the stadia rod using a piece of
tape or a dry erase marker. Then relocate the stadia rod and stand it up at the RPI
location. Select the vertical tangent reading setting on the
theodolite and then site in on the stadia rod placing the crosshairs of the
view scope on the top edge of the tape or dry erase mark. The number indicated on the LED display screen represents
the degree. This difference can be no
greater than positive 3°or -1° degree.
6. The Azimuth Perpendicular to the Runway Centerline known
as the (AZP) is the number of degrees that the theodolite must swing from AZRP
in order to complete a 90 degree turn and present a perpendicular angle from
the proposed radar site to the Runway Centerline. AZP is calculated using the formula depicted
on the slide. A positive number indicates the theodolite will swing to the
right, while a negative number indicates the swing will be to the left.
7. After swinging the theodolite to the indicated AZP;
measure the distance from Radar to Runway Centerline; this is the (DRCL) and it
is measured in feet. The DRCL can be no closer than 150 feet and no further than
600 feet. Once the DRCL has been determined; the DTD and DTH can then be
calculated. Use the formulas depicted on the slides to complete these steps.
8. The Azimuth Bore sight Offset (AZO) is the number of
degrees that the theodolite must swing from AZRP to indicate the point where
the Bore Sight marker is to be placed. A positive number indicates the
theodolite will swing to the right, while a negative number indicates the swing
will be to the left.
The Azimuth to Bore sight (AZB) is the point from which an
imaginary straight line angle is envisioned from the bore sight marker to the
Proposed Radar Site and used as a reference to align the sensor vehicle onto
the proposed site. The formulas for
these calculations are depicted on the slide.
9. Once the sensor vehicle is aligned, the vehicle is placed
in the operational configuration with both the Precision Approach (PAR) and
Airport Surveillance Approach (ASR) Radar antennas fully deployed.
The bore sight scope is then mounted onto the side of the
PAR antenna and a marker is place at the point of the crosshairs as viewed
through the scope at a distance parallel to the original bore sight
marker.
Using the theodolite, measure the amount of the swing
between the original bore sight marker and the new bore sight marker.
10. The number displayed on the LED screen is the Angle of
Correction or (ACOR). The ACOR is the
difference in degrees and tenths of degrees between the Original Bore Sight Marker and the New Bore Sight
Marker. This difference can be no
greater than 1°.
Determine the Range to Touchdown or (RTD) by performing the
calculation depicted on the slide. The
RTD is the straight line distance from the Proposed Radar Site to RPI.
11. HPA or height of antenna bottom edge is measured from
the ground to the bottom edge of the PAR antenna after the sensor vehicle has
been placed in the operational configuration.
Use the calculation formula depicted on the slide to complete this step.
12. ELP or Elevation To Point Of Intercept is the elevation
difference measured in tenths of degrees from the PAR antenna in its full
operational configuration to RPI. It is derived from the formula depicted on
the slide.
13. The PAR Alignment Angle known as (PAA) is a measurement
used by the database management system during the computer configuration
process. It is derived from the formula
depicted on the slide and is expressed in tenths of degrees.
14. The PAR Bore Sight Angle known as (PBA) is a measurement used by the database management system during
the computer configuration process. It
is derived from the formula depicted on the slide and is expressed in
hundredths of degrees.
