SAR Universal Mapping System (UMS)

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The UMS originated among rescue organizations in Washington state during the 1960s, and has now become the standard among air search crews for reaching proper target areas.  Although air search is not our focus, it is not uncommon for them to coordinate with ground teams, and therefore it is necessary to know enough about this system either to call up air searchers or for them to call in ground teams for closer reconnaissance. 

UMS Sectors

Aviators use 1:500000 maps they call "sectionals" that have 15' latitude x 15' longitude grid sectors.  Each complete sectional goes by a three-letter code for its principal air traffic control tower.  Each sector then has its own numerical label, and these each have quarter sectors (7.5' x 7.5', which is the same as a standard 1:24000 USGS topographic map) that receive letter labels.  "A" is always the northwest quarter sector, "B" the northeast, "C" the southwest, and "D" the southeast.

For specifying more precise positions within a lettered quarter sector, pilots use a four-digit code and measure from the upper right corner of the sector.  The measurements are in nautical miles and tenths (NM; 1 NM equals 1' of latitude).

For example, the UWSP Science Building (see map below) would have the following UMS specification:

GRB 462 D 1558  

(meaning the Green Bay sectional, sector 462, 1.5 NM west and 5.9 NM south of the northeast corner of the southeast quarter).  You can see for yourself the potential for miscommunication if that came over a radio verbally, whereas knowing the UMS code reduces the prospect for error.      [BACK]

On the map below, the Chicago sectional (ORD for O'Hare) begins a little more than 30 NM south of Stevens Point.   Note the quartering for GRB 530 at Oshkosh.

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