Lat/Lon - Tile Formulas

[Guest]

Ok, Im confused.I thought I thoroughly understood lat/lon conversion formulas. I still think I have them right, because the database work I've done all lined up great... but I notice I cant teleport below 85

[Guest Colins2]

BradIt's the way that the Fly! world is projected.85

[Guest]

Could you please post it here, Colin? Or mail it to me, too. :-)nick@nik2.com

[Guest Colins2]

NickHere is the formula:With an already declared array double zlat[256];void makelat(void){zlat[128]=0;zlat[127]=-1.40625;zlat[129]=1.40625;// northern hemispherefor(int z=130;z<256;z++){ zlat=zlat+(1.40625 *cos(zlat/ RAD)); }//southern hemispherefor(int z=126;z>=0;z--){ zlat=zlat-(1.40625 *cos(zlat/ RAD)); }}(You have to replace the < > with square brackets)1.40625 = 360/256 and is the constant for the longitude boundaries, they never change.It is a form of Mercator projection that varies the lattitude scale so that the longitude scale remains the same.I've also sent you a mail with a spreadsheet.Colin

[Guest]

Ok, I finally got a chance to check out the spreadsheet you sent me Colin, but im a bit confused.If im reading your spreadsheet correctly...for GlobeTile 172:153You list latitudes of (assuming 173 is upperbounds of 172)173

[Guest Colins2]

BradYou are reading the globe tile numbers wrongly.the globe tile numbering is transverse mercator, i.e. long:lat.In the example lattitude is tile 153 and longitude is 172.Colin

[Guest]

Doh!Thanks