Launch image choose longer - ios

Question

I have a universial app .I added Launch images to project .
I want to wait splash screen until download json from webservice. my app it's waiting until download json. but launch image choosing is not correct or position.I wrote this following code.for example: my launch image correct on iphone 5 . but not on iphone 3gs.
How can I do that easily? sorry my English . Thank you.
CGRect screenRect = [[UIScreen mainScreen] bounds];
float screenWidth = screenRect.size.width;
float screenHeight = screenRect.size.height;
splashView=[[UIImageView alloc] initWithFrame:CGRectMake(0, 0, screenWidth, screenHeight)];
float sysVer = [[[UIDevice currentDevice] systemVersion] floatValue];
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone)
{
NSLog(#"height %f version %f",[[UIScreen mainScreen] bounds].size.height,sysVer);
if (sysVer <7.0)
{
// iOS-6.01 and prior code
if (screenHeight==480)
{
splashView.image=[UIImage imageNamed:#"Default"];//iPhone
}
else if (screenHeight == 568.0f)
{
splashView.image=[UIImage imageNamed:#"Default-568h#2x.png"];
}
}
else // for ios7
{
if (!screenHeight == 568.0f)
{
splashView.image=[UIImage imageNamed:#"Default"];//iPhone
}
else
{
splashView.image=[UIImage imageNamed:#"Default-568h#2x.png"];
}
}
}
else
{
if (sysVer <=6.1)
{
splashView.image=[UIImage imageNamed:#"Default-Portrait"];// iPads
}
else
{
splashView.image=[UIImage imageNamed:#"Default-7681024"];// iPads
}
}
[self.view addSubview:splashView];
log is on iphone 3gs
height 480.000000 version 6.100000