BOOKS OF RtfiDIfGS - PAHO/WHO

REVELLE
ET AL.
HALTOI
SERVICUS
RESEARCH
- 299 -
Fig. 2. A solution to the locatino set covering
problem. Facilitiea (circled dots) are placed so that
all demand points and 100 percent of the
populatiun are witiin 15-unit limits (jolid lines\
from some facility. Dashed linres are 10-unit limits
from cach facility; they enclose only :31 ¡perccnt
ol tihe populalion.
placed facilities will cover 90 pcrcent ofl tle dcimamidi. elic (litcstioi
is imrnediately apparent: are t!he four aduidiioinal la ilitics wortlh
their cst. wben thiey cover only the last 10 pertent of the denm;md?
The location et covering muodcl would Iave yielded only the inforination
underlying point 13 of thc grapih.
Solutions available from thie locatíio set coceting miodel are
rigid. in that all points must be coveedsl; ini additioun, the sohltions
are not "tight." Extensive computatioinal experience indicates tihat
the mininimuni nunmber ol lacilities to provitde :over mu;y br ;a¡r;aiged
in many ways without significaultly violatinig the futd.ilidimt:il uovirage
standard. Applictaion of the mi.íxiíiil. *osc iti¡g niKlCl *a0t oftCi
improve on solutions oblainable Irom thle lc;ilio e' t i>is¡ls. liiws ii ¡: g I. I .íi¡