Geographic information software programs' accuracy for interfacility air transport distances and time

Abstract

Introduction: This study aimed to evaluate consistency/predictability of interfacility flight times (IFFTs) and accuracy of geographical information system (GIS) software packages for estimating IFFT.

Methods: This retrospective study conducted by a program using a Bell 206 assessed the first 1000 IF transports occurring on 137 "runs" (ie, referring-receiving hospital pairings) made at least twice. GIS IFFT estimates using Google Earth™ (GE) and ArcGIS™ (AG) were compared against actual IFFT using linear regression; univariate analysis included assessment of medians with 95% binomial exact confidence intervals (CIs). Interrater agreement for GIS was assessed with κ.

Results: GE and AG estimates fell, respectively, within 1 mile of actual in 136/137 runs (99%, 95% CI 96%-100%) and 130/137 runs (95%, 95% CI 90%-98%). GE- and AG-predicted IFFT strongly (P < .001) correlated with, underestimating by about 2 minutes, actual IFFT (GE: r2 0.93, coefficient 0.98, 95% CI .97-1.00; AG: r2 0.93; coefficient 0.98, 95% CI .96-1.0). GE and AG had statistically equivalent (κ > .8), "almost-perfect," interrater agreement.

Conclusion: IFFTs for same-run helicopter EMS transports in our rural state setting are characterized by little variability. GIS is highly accurate in predicting IF logistics, with public-domain GE performing as well as more expensive AG.