Editing Megacity (section)

==Urban Metric System==
{{main|Settlement hierarchy}}
{{rewrite section|date=February 2025}}
Since, presently, urban data are based on arbitrary definitions that vary from country to country and from year or census to the next, making them difficult to compare, an Urban Metric System (UMS) has been conceived that could correct the problem,<ref>{{cite web |url=https://authors.elsevier.com/sd/article/S1757-7802(24)00342-1|title=Estimating urban sprawl standards by means of the Urban Metric System |last1=Tellier |first1=Luc-Normand |last2=Quesnel |first2=Frédéric |last3=Bur |first3=Justin |publisher=Regional Science Policy and Planning |date=November 2024 }}</ref> since it allows computing the urban area limits and central points, and it can be applied in the same way to all past, present and future population and job distributions. 

It is based on vector field calculations obtained by assuming that, in a given space, all inhabitants and jobs exert the same attractive force ''A'' and repulsive force ''R''. The net force (''A'' - ''R'') exerted by each inhabitant or job is given by [1/(1 + ''d'')] - [1/( ''β'' + ''d''/2)], where ''d'' = distance and ''β'' is the only parameter. 

UMS distinguishes the following types of urban areas(including "patropolises" that are tantamount to "megacities"), each type corresponding to a given value of ''β'':
{| class="wikitable"
|+
!
!Urban area
!Distance at which the attractive force = the repulsive force 
!Value of ''β''
|-
!1
!Central city
!10 km
!6
|-
!2
!Agglomeration
!20 km
!11
|-
!3
!Metropolis
!40 km
!21
|-
!4
!Patropolis
!80 km
!41
|-
!5
!Megalopolis
!160 km
!81
|-
!6
!Urban system
!320 km
!161
|-
!7
!Urban macrosystem
!640 km
!321
|-
!8
!Continental system
!1,280 km
!641
|-
!9
!Intercontinental system
!2,560 km
!1,281
|-
!10
!World system
!5,120 km
!2,561
|}

UMS has been applied to some Canadian cases since 2018, but the data presented in this article are still based on the various existing national definitions, which are disparate.