The following table of units of measurement will be used by aeronautical stations within the Riga FIR.

FOR MEASUREMENT OF	UNITS USED
Distance used in navigation, position reporting, etc. - generally in excess of 2 nautical miles	Nautical Miles and tenths
Relatively short distances such as those relating to aerodromes (e.g. runway lengths)	Metres
Altitudes, elevations and heights	Feet
Horizontal speed including wind speed	Knots
Vertical speed	Feet per minute
Wind direction for landing and taking off	Degrees Magnetic
Wind direction except for landing and taking off	Degrees True
Visibility including runway visual range	Kilometres or Metres
Altimeter setting	Hectopascal
Temperature	Degrees Celsius
Weight	Metric tons or Kilograms
Time	Hours and Minutes, a 24-hour day beginning at midnight UTC

Co-ordinated Universal Time (UTC) is used by navigation services and in publications issued by the Aeronautical Information Service. Reporting of time is expressed to the nearest minute, e.g. 12:40:35 is reported as 1241.

In the AIP and associated publications, the expression “summer period“ indicates the part of the year in which the “daylight saving time“ is in force. The other part of the year will be named the “winter period“. Daylight saving time in Latvia is UTC plus 3 hours.

The “summer period“ will be introduced every year on the last Sunday in MAR at 0100 UTC and it will cease on the last Sunday in OCT at 0100 UTC.

Times applicable during the “summer period“ are given in brackets. Local time in Latvia is:

• UTC plus 2 HR, during the winter period;
• UTC plus 3 HR, during the summer period.

1. Name/designation of the reference system

All published geographical co-ordinates indicating latitude and longitude are expressed in terms of the World Geodetic System - 1984 (WGS-84) geodetic reference datum.

2. Identification and parameters of the projection

The projection is expressed in terms of Universal Transverse Mercator (UTM).

3. Identification of ellipsoid used

The ellipsoid is expressed in terms of World Geodetic System -1984 (WGS-84) ellipsoid.

4. Identification of the datum used

The World Geodetic System -1984 (WGS-84) is used.

5. Area(s) of application

The area of application for the published geographical co-ordinates coincides with the area of responsibility of the Aeronautical Information Service, i.e. the entire territory of the Republic of Latvia as well as the airspace over the high sea encompassed by the Riga Flight Information Region in accordance with the regional air navigation agreement.

6. Use of asterisk to identify published geographical co-ordinates

Not applicable.

1. Name/designation of the reference system

The vertical reference system used is Latvian normal height system at epoch 2000,5.

2. Description of geoid model used

The quasigeoid model LV'14 is used, the accuracy of LV'14 is 4.0 cm. The model is available on the website of Latvian Geospatial Information Agency https://www.lgia.gov.lv/en/latvian-quasi-geoid-model

The differences between LV'14 and Earth Gravitational Model 1996 (EGM-96) vary from -21 cm to 80 cm in the territory of Latvia.

LV'14 and EGM-96 difference surface, description of its preparation, difference conversion calculator are available on the website of Latvian Geospatial Information Agency https://www.lgia.gov.lv/en/latvian-quasi-geoid-model-lv-14-and-earth-gravitation-model-1996-egm-96

3. Use of asterisk to identify published elevations/geoid undulations

Not applicable

The nationality mark for aircraft registered in the Republic of Latvia is the letters YL. The nationality mark is followed by a hyphen and a registration mark consisting of 3 letters e.g. YL-AAA.

NAME	DATE/DAY
New Year’s Day	01 JAN
Good Friday	FRI before Easter
First Easter	Easter SUN
Easter Monday	MON after Easter SUN
Labour Day	01 MAY
Independence Declaration Day	04 MAY
Mother’s Day	2nd SUN of MAY
Pentecost	7th SUN after Easter
Ligo Day	23 JUN
Janis Day	24 JUN
Independence Day	18 NOV
Christmas Eve	24 DEC
Christmas Day	25 DEC
Boxing Day	26 DEC
New Year’s Eve	31 DEC