Visibility Chain at Regional Airports in the Netherlands

Wiel Wauben

R&D Information and Observation Technology

TECO 2012 | Visibility Chain2

Introduction

• KNMI automated the aeronautical observations at regional civil

airports, the so-called AUTO METAR system.

• During the evaluation many questions related to visibility arose.

• It was realized that documentation was scattered between

departments and incomplete; not always verified against current

practices or ICAO requirements and recommendations;

background of deviations were sometimes unclear (requirements

old system or by local agreement?).

review of visibility chain against WMO 2008, 2010, ICAO 2005,

2006, 2010 and KNMI handbooks, reports and (manufacturer’s)

system documentation, work instructions and configurations.

TECO 2012 | Visibility Chain3

Visibility Chain

• Public KNMI internal document (

http://www.knmi.nl/bibliotheek/knmipubIR/IR2012-02.pdf

• Contents

11. Server and client network systems12. System monitoring and data validation13. Continuous remote verification14. Derivation of VIS and RVR15. Averaging of VIS and RVR16. Selection and backup of VIS and RVR17. Available VIS and RVR variables18. Meteorological reports19. Technical infrastructure20. Data flow21. Conclusions and recommendations

1. Introduction2. Sources of meteorological information for users3. Definitions of visibility4. Causes of visibility reductions5. Visibility requirements6. Sensors for the measurement of MOR7. Calibration of MOR measurements8. Maintenance and effect of contamination9. Sensor locations10. SIAM sensor interface and MUF cascade

TECO 2012 | Visibility Chain4

Visibility requirements

• WMO (2008) specifies the range of RVR as 10 to 1500 m, whereas

ICAO (2010) recommends a RVR range from 50 to 2000 m.

• The requirements for background luminance are not clearly stated.

Range given in examples and ICAO (2006) only mentions that an

uncertainty of ±10 % is considered acceptable.

MOR (SYNOP Vm, VV) VIS (METAR/ACTUAL VVVV) RVR (METAR/ACTUAL VRVRVRVR) Range (Step) Accuracy Range (Step) Accuracy Range (Step) Accuracy

0-100 m (10) - 0-800 m (50) * 50-400 m (25) ±10 m 100-5000 m (100) * 800-5000 m (100) * 400-800 m (50) ±25 m

5-30 km (1) ±20 % 5-10 km (1) ±20 % 800-1500 m (100) ±10 % 30-70 km (5) ±20 % ≥10 km 1500-2000# m (100) ±10 %

>70 km >2 km *MOR and VIS accuracy: ±50 m for MOR≤600m; ±10 % for 600<MOR≤1500m; and ±20 % for MOR>1500m. #RVR is reported up to 2000 m at civil airports, but up to 3000 m at military airbases in The Netherlands (KNMI, 1994). Note that RVR values outside the range are reported as M0050 and P2000 or P3000.

TECO 2012 | Visibility Chain5

Calibration of MORmeasurements

• Reference restricted to MOR < 1500 m and without precipitation!?

Furthermore the linearity of the sensor over the MOR range is not

verified.

• Background luminance checked via calibrator of manufacturer.

Traceability is currently under review.

Transmitter ↑

SB receiver ↑

FD12P ↑LB receiver →

• A field reference setup of TMM

and FS is used the transfer the

calibration of the TMM to the

FS by means of a so-called

scatter plate.

TECO 2012 | Visibility Chain6

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

0

100000

200000

300000

400000

500000

S

um c

ount

MOR (m)

FD12P HSS

linearity FS

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0

1000

2000

3000

4000

Cou

nt

MOR (m)

FD12P HSS

TECO 2012 | Visibility Chain7

Maintenance and effect of contamination

• Flying insects in the measurement volume of the FS sensor can

give significant reductions of the MOR.

• The solution ... ? see poster P1(28)!

• Describes the maintenance

and monitoring of lens

contamination level and the

effect of contamination of the

MOR measurements.

TECO 2012 | Visibility Chain8

Selection and backup of VIS and RVR

• No backup of VIS/RVR at touchdown by FS at other end of RWY in local MET

report (arrival).

• Backup of background luminance is allowed.

• Usage of video camera’s to determine whether VFR conditions apply in

case of sensor failure, but quality images too poor.

KVS1

Technical room KNMI

W = windZ = visibility / weatherC = cloudU = temperature / humidityP = pressureQ = radiationR = precipitationO = video camera

↓↑WP ZRUQCWPUZ

KVS2

24↓↑ 06

Threshold

Aiming point

Threshold

Aiming point

TECO 2012 | Visibility Chain9

Data flow

ZAs Backup ZAsb

ZMm ZMa ZAm ZAa

Vis Va Vab

Visibility ZMs ZAs

Vis Average Va Backup Vab

List MR/Va

RVRraw ZMs ZAs

RVRopt

Average RVRm

Sum RLL

BB Backup BBb

BBm

RwName

RVRBooleanm

ZMm ZMa ZAm ZAa

Process

Average RVRa List

MR/RVRa MR/RVRn MR/RVRx MR/RVRt

MinMax

RVRtend

RVRn RVRx

RVRt

RVRBoolean RVRBoolean

Backup RVRBooleanb

w’w’ RE

MetarPWC

MR/w’w’2 RE

List

VertVis Cloud

I fElse

MR/Vn

A/RVR

A/VertVis M/VV

M/w’w’ M/RE

A/Vn

A/Rn1 M/RN1

M/Vx

M/RV1 M/RV1n M/RV1x M/RV1t

ZMs 12Sec SIAM data Vis 12Sec derived data ZMm 1Min data MR/Vn runway dependent data A/Rn1 local report data M/Vx METAR data ZAsb proposed change

CodeExtract

Requested if RVRBoolean

Median

CIBIL

A/w’w’_MLR

Vprev

MetarPWC

Vm Average

TECO 2012 | Visibility Chain10

Conclusions

• The review of the visibility chain was appreciated by internal and external users.

• During the review some errors in the chain could be pointed out. Some of these

were directly solved, but others require consensus between parties involved

and/or further investigations.

• The recommendations (37) are managed in a spreadsheet. Persons have been

assigned, but items have not yet been prioritised and sometimes their impact is

unclear. Meanwhile new items have been added to the list.

• The maintenance of the document is still under discussion. Inclusion in Dutch

handbook on observations versus coupling to documentation of the underlying

systems, regulations and agreements.

TECO 2012 | Visibility Chain11

A useful contribution

• Track changes in WMO / ICAO documentation e.g. used in proposals for

the amendment of Annex 3 and including rationale!