Set variables:

local MapScales = {
    [0] = {[0] = {x=0.0000000001,y=0.0000000001}}, -- overworld dummy

    [-1] = { -- Battlegrounds
        [0] = {x=0.0000000001,y=0.0000000001}, -- dummy
        ["Alterac Valley"] = {x=0.00025277584791183,y=0.0003791834626879}, -- alterac
        ["Arathi Basin"] = {x=0.00060996413230886,y=0.00091460134301867}, -- arathi
        ["Warsong Gulch"] = {x=0.000934666820934484,y=0.0013986080884933}, -- warsong
    },

    [1] = { -- Kalimdor
        [0] = {x=0.0000000001,y=0.0000000001}, -- dummy
        [1] = {x=0.00018538534641226,y=0.00027837923594884}, -- Ashenvale
        [2] = {x=0.0002110515322004,y=0.00031666883400508}, -- Aszhara
        [3] = {x=0.00016346999577114,y=0.0002448782324791}, -- Darkshore
        [4] = {x=0.001011919762407,y=0.0015176417572158}, -- Darnassus
        [5] = {x=0.000238049243117769,y=0.00035701000264713}, -- Desolace
        [6] = {x=0.000202241752828887,y=0.00030311250260898},  -- Durotar
        [7] = {x=0.00020404585770198,y=0.00030594425542014}, -- Dustwallow
        [8] = {x=0.00018605589866638,y=0.00027919347797121}, -- Felwood
        [9] = {x=0.00015413335391453,y=0.00023112978254046}, -- Feralas
        [10] = {x=0.00046338992459433,y=0.00069469745670046}, -- Moonglade
        [11] = {x=0.00020824585642133,y=0.00031234536852155}, -- Mulgor
        [12] = {x=0.00076302673135485,y=0.0011450946331024}, -- Orgrimmar
        [13] = {x=0.00030702139650072,y=0.00046115900788988}, -- Silithus
        [14] = {x=0.0002192035317421,y=0.00032897400004523}, -- Stonetalon
        [15] = {x=0.00015519559383392,y=0.00023255497217178}, -- Tanaris
        [16] = {x=0.00021010743720191,y=0.00031522342136928}, -- Teldrassil
        [17] = {x=0.0001055257661002,y=0.00015825512153762}, -- Barrens
        [18] = {x=0.00024301665169852,y=0.00036516572747912}, -- Needles
        [19] = {x=0.00102553303755263,y=0.0015390366315842}, -- Thunderbluff
        [20] = {x=0.00028926772730691,y=0.0004336131470544}, -- Ungoro
        [21] = {x=0.0001503484589713,y=0.0002260080405644}, -- Winterspring
    },

    [2] = { -- Eastern Kingdoms
        [0] = {x=0.0000000001,y=0.0000000001}, -- dummy
        [1] = {x=0.00038236060312816,y=0.00057270910058703}, -- Alterac mountains
        [2] = {x=0.00029711957488741,y=0.00044587893145425}, -- arathi
        [3] = {x=0.00043004538331713,y=0.00064518196242196}, -- Badlands
        [4] = {x=0.00031955327306475,y=0.00047930649348668}, -- blasted lands
        [5] = {x=0.00036544565643583,y=0.00054845426763807}, -- Burning steppes
        [6] = {x=0.00042719074657985,y=0.00064268921102796}, -- deadwind pass
        [7] = {x=0.00021748670509883,y=0.00032613213573183}, -- Dun Morogh
        [8] = {x=0.00039665134889739,y=0.000594192317755393},-- duskwood
        [9] = {x=0.00027669753347124,y=0.00041501436914716}, -- EPL
        [10] = {x=0.00030816452843802,y=0.00046261719294957}, -- Elwynn Forest
        [11] = {x=0.00033472904137203,y=0.00050214784485953}, -- hillsbrad
        [12] = {x=0.0013541845338685,y=0.0020301469734737}, -- Ironforge
        [13] = {x=0.00038827742849077,y=0.000582420040021079}, -- loch modan
        [14] = {x=0.00049317521708352,y=0.0007399320602417}, -- redridge mountains
        [15] = {x=0.00047916280371802,y=0.00071918751512255}, -- Searing G.
        [16] = {x=0.00025506743362975,y=0.00038200191089085}, -- silverpine
        [17] = {x=0.00079576990434102,y=0.0011931381055287}, -- Stormwind
        [18] = {x=0.00016783603600093,y=0.00025128040994917}, -- stranglethorn
        [19] = {x=0.00046689595494952,y=0.00070027368409293}, -- swamp of sorrows
        [20] = {x=0.0002777065549578,y=0.00041729531117848}, -- Hinterlands
        [21] = {x=0.00023638989244189,y=0.0003550010068076}, -- Tirisfal
        [22] = {x=0.0011167100497655,y=0.0016737942184721}, -- Undercity
        [23] = {x=0.00024908781051636,y=0.00037342309951782}, -- WPL
        [24] = {x=0.00030591232436044,y=0.00045816733368805},-- westfall
        [25] = {x=0.00025879591703415,y=0.00038863212934562}, -- wetlands
    }
}
local Continent = 1
local Zone = 1
local ZoneName = ""
local UnitID = "party1"
local px, py = 0, 0
local ux, uy = 0, 0
local distance = 0

Set Event:

elseif event == "ZONE_CHANGED_NEW_AREA" then
        SetMapToCurrentZone()
        Continent = GetCurrentMapContinent()
        Zone = GetCurrentMapZone()
        ZoneName = GetZoneText()
        UnitID = "party1"
        if ZoneName == "Warsong Gulch" or ZoneName == "Arathi Basin" or ZoneName == "Alterac Valley" then Zone = ZoneName end


print distance:

function VHM:GetMapScale()
    if VHM.GetNumPartyMembers() > 0 then
        px, py = GetPlayerMapPosition("player")
        ux, uy = GetPlayerMapPosition(UnitID)

        distance = sqrt(((px - ux)/MapScales[Continent][Zone].x)^2 + ((py - uy)/MapScales[Continent][Zone].y)^2)
        DEFAULT_CHAT_FRAME:AddMessage(distance)
    end
end