2011 Policy and Aviation Contract Language References
Regarding Appropriate Latitude Longitude Datum and Format
USFS National Aviation Safety and Management Plan:
The method of flight following for Fire incidents is documented on an Aircraft Resource
order or in a Dispatch Center’s Mobilization/Operating Guide. The method for flight
following non-fire resource missions will be documented in a Project Aviation Safety
Plan (PASP) and/or Flight Request/Flight Schedule form.
BLM National Aviation Plan:

The specific format to be utilized for the latitude – longitude coordinates for flight
following check-in points, etc., must be discussed and agreed upon by dispatch and the
flight crew to assure accurate navigation. The format for aviation operations is Degrees
Decimal Minutes (DDM). Reference BLM NAP Appendix 4 for additional details.
Appendix 4 – Latitude/ Longitude Information
If coordinates are wrong…
 Risk/danger/liability goes up
 Calculations become erroneous (weight/distance/fuel ratios)
 People can’t find the “right” spot
 Data goes onto maps in the wrong place
 We look bad as an organization, a unit, an individual
 Contractors/pilots become angry/confused/frustrated
Latitude
 Parallel east-west lines
 Measures 90o North and 90o South of equator
Longitude
 Lines run south to north.
 Measures east and west of the prime meridian
 Lines converge at North and South poles
Common Formats
Format
Example
Degrees Decimal Degree (DD)
N 64.84052o by W 147.60437o
Degrees Decimal Minutes
(DDM)
N 64o 50.431’ by W 147o 36.262’
Degrees Minutes Seconds
(DMS)
N 64o 50’ 25.9” by W 147o 36’ 15.7”
Notation
 Degrees: o
 Minutes: ’
 Seconds: ”
 Decimal: .
 Hemisphere: N, S, E, W, -
On-line Calculators for converting between Formats:
http://www.fcc.gov/mb/audio/bickel/DDDMMSS-decimal.html
http://www.calculatorcat.com/latitude_longitude.phtml
GPS Datums
 Datums define the origin and orientation of latitude/longitude lines
 Describing a place by lat/long is not good enough. The datum must also be stated.
 Changing the datum changes the lat/long of a point on the surface of the Earth
 There are hundreds of different Datums, agencies use different Datums.
 Referencing Lat/ Long coordinates to the wrong datum can result in position errors of hundreds of
meters
Know your agency’s standard Format and Datum
 Aviation (DDM, WGS84)
 BLM GIS (Various)
 TFRs (DMS, WGS84)
 Fire (Various)
Remember…
 Use only ONE period/decimal point when writing a latitude or longitude in DD, or DMS.
 Do NOT use periods/decimal points for degrees or minutes when writing a latitude or longitude in
DMS
 There can NEVER be more than 60 seconds in DMS format
 Do NOT mix formats
 Know and use proper Datum
Aircraft Contract Language
BLM Exclusive Use helicopter contract language: (Note: Excerpt is from Lakeview BLM contract.)
Technical Specification:
B7.4 Navigation System:
B7.4.1 One permanently installed, panel mounted global positioning system (GPS), utilizing an
approved, fixed external aircraft antenna and powered by the aircraft electrical system or an aviation
portable GPS unit (Garmin GPS Map 296/396/496 or equivalent) provided the portable unit is securely
mounted, is equipped with a remote (i.e. not part of the GPS unit) antenna, and presents information from
an overhead orientation (not a drive-along-the-road type), and is powered by the aircraft electrical system.
The GPS (permanently installed or portable) must utilize the WGS-84 datum and reference latitude and
longitude coordinates in the degrees/minutes/decimal minutes (DM mode) for aircraft positioning.
B7.4.2 A second GPS (GPS-2), which must also utilize the WGS-84 datum, reference latitude and
longitude coordinates in the degrees/minutes/decimal minutes (DM mode) for aircraft positioning; utilize
an approved, fixed, external aircraft antenna; and be powered by the aircraft electrical system.
B20.6 Flight following: Pilots are responsible for flight following with the FAA, ICAO, and/or in accordance
with the DOI bureau’s approved procedures. Check in intervals must not exceed one hour intervals under
normal circumstances.
Note: This exact same language is found in the Jan. 2011 DOI “On-Call Small Helicopter”
Solicitation #N10PS30009.
The 2011 DOI Air Tactical Fixed Wing contract:
Sec. B 7.4 Navigation Systems
B7.4.1 One permanently installed, panel-mounted Global Positioning System (GPS). The GPS must
utilize the WGS-84 datum, reference latitude and longitude coordinates in the degrees/minutes/decimal
minutes (DM) mode for aircraft positioning; utilize an approved, fixed, external aircraft antenna; and be
powered by the aircraft electrical system. The GPS installation must be FAA-approved (or approval
pending). Handheld and/or marine type equipment is not acceptable.
2010 USFS Air Tanker Solicitation
SECTION J – LIST OF ATTACHMENTS
EXHIBIT 3 - AVIONICS
8.
Navigation Systems
a) One Global Positioning System (GPS). The GPS shall be panel-mounted; permanently installed in the
aircraft; utilize WGS-84 datum; reference latitude and longitude coordinates in the DM
(degrees/minutes/decimal minutes) mode; utilize an approved, fixed, external aircraft antenna; and be
powered by the aircraft electrical system. The GPS unit must have the ability for manual entry of
waypoints in flight. The GPS shall have a database (VFR units not over one (1) year old or approachcertified IFR units not over 28 days old) covering the continental United States and Alaska. Handheld
and/or marine type equipment is not acceptable.
2009 USFS/DOI Type 1 and 2 CWN Helicopter contract
C-8 B Navigation Systems
One Global Positioning System (GPS). The GPS shall be panel mounted; located where both the pilot
and co-pilot/observer can clearly view the display; utilize WGS-84 datum; reference latitude and longitude
coordinates in the DM (degrees/minutes/decimal minutes) mode; and be powered by the aircraft electrical
system.
2011 DOI On-Call SEAT Contract
B7.4.1 One permanently installed, panel-mounted global positioning system (GPS) utilizing an
approved, fixed external aircraft antenna and powered by the aircraft electrical system or an
aviation portable GPS unit (Garmin GPSMap 296/396/496 or equivalent) provided the portable
unit is securely mounted, is equipped with a remote (i.e., not part of the GPS unit) antenna, and
presents information from an overhead orientation (not a drive-along-the-road type), and is
powered by the aircraft electrical system. The GPS (permanently installed or portable) must
utilize the WGS-84 datum and reference latitude and longitude coordinates in the
degrees/minutes/decimal minutes (DM) mode for aircraft positioning.
Mobilization Guide language:
National Mobilization Guide, Section 26.
Aircraft Mobilization
When a Geographic Area has depleted local and available aircraft resources, request(s) will be
placed with NICC. Aircraft assigned will become the receiving Area’s resource until released.
The following terminology will be used when requesting aircraft through NICC:
• Knots (kts) will be the standard term used to reference airspeed.
• VORs (Very High Frequency Omni-directional Range) will be used to reference direction.
• Latitude and longitude must be provided in degrees and minutes.
• Aircraft registration numbers will be used when referencing helicopters, lead planes, and
air attack aircraft. Airtankers and SEAT’s will be referenced by the airtanker number;
e.g., T-00.
Driving a national decision to adopt one format vs. another has been a contentious issue for over ten
years. Pilots prefer Degrees/Decimal Minutes. The FAA requires Degrees Minutes Seconds for
identifying the center point of a TFR. Virtually all aircraft contracts call for vendors to have GPS
equipment onboard that is capable of providing Lat. Long info. in Degrees/decimal Minutes.
Some GPS units can be set to provide the info. in either format.
Does it really matter which format is used for applications other than TFR Center points?
If there are far too many strong opinions to contend with, does it really matter whether everything is
standardized in one format vs. another and whether a hard and fast rule or policy must be implemented?
If there is confusion in how Lat. Long. information is relayed from the air (or the field) to Dispatch (and
vice versa) via radio, or how information is recorded, perhaps it is more of an internal procedural and
training issue that can be resolved with training and applied with discipline. Here is what I propose:
Confusion may be eliminated if the user specifically clarifies which format is being used by using the word
"seconds" or “point” in the radio transmission.
If providing a latitude in degrees and decimal minutes of 41 deg. 36.50 minutes, the person on the radio
must state either “Four One degrees point 50 minutes” or “Four One degrees decimal 50 minutes.”
If they are relaying the same latitude using degrees minutes and seconds, they must use the word
“seconds” in their transmission; “41 degrees, 36 minutes, 30 seconds.” If one does not mismatch the
words “point” (or “decimal”) and “seconds,” and they are disciplined to always state one of these words or
the other, there should be no confusion. People should never use the word “point” when they are using
degrees minutes and seconds in a transmission.
If an ATGS is requesting a TFR and is giving a specific Lat. Long for the requested centerpoint, they need
to use Deg. Min. Seconds, and make the correct radio call using proper phraseology, and use the word
“seconds” in the transmission.
If a user does not follow this discipline, and/or if a dispatcher is not clear on which format is being relayed,
the question must be asked which Latitude Longitude format is being utilized. Dispatchers should not care
(other than on TFR requests) which method is being utilized as long as the person on the radio clearly
states which format they're using.
It would be most appropriate if all applications used the same format. Since a cultural change of this
magnitude does not appear to be possible in our organization, and since so many individuals have strong
opinions in the matter, then the only viable solution lies in how radio users clearly define which method
we are using at any given time.
Pilots, especially those on IFR flight plans, learn very quickly to utilize the proper phraseology when
communicating with Air Traffic Control (ATC). When they fail, ATC historically has little patience and will
sometimes sharply reprimand the pilot on the air. Furthermore, when a pilot is requesting a clearance to
a more direct route or to an altitude with more favorable winds, those who use proper phraseology with
ATC get what they want, and those who cause problems for ATC are sometimes routed to a less-direct or
efficient route, or are forced to wait longer for their clearances. Pilots quickly learn how to “play the
game” since it results in better and more timely service from the controllers. So….. If pilots can be
trained to use proper phraseology with discipline…….