call SetMapToCurrentZone() if zones changes! "ZONE_CHANGED_NEW_AREA" event

use GetCurrentMapZone() to get the index number

example to check distance for UnitID = function, works only for Eastern Kingdoms!:

function VHM:GetMapScale()
    if VHM.GetNumPartyMembers() > 0 then
        SetMapToCurrentZone()
        local UnitID = "party1"
        local px,py = GetPlayerMapPosition("player")
        local ux,local uy = GetPlayerMapPosition(UnitID)

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

MapScales = {
-- Kalimdor
    [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

-- Eastern Kingdoms
    [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
}