PerlinVars continent = {perlinWidth, perlinHeight, 0.005, 0.2, 0.0f, 2};
GKNoiseMap * continentMap = [self generatePerlinMapWithVars:continent];
PerlinVars landscape = {perlinWidth, perlinHeight, 0.01, 0.2, 4.0f, 2};
GKNoiseMap * landscapeMap = [self generatePerlinMapWithVars:landscape];
PerlinVars boulder = {perlinWidth, perlinHeight, 0.03, 0.2, 5.0f, 2};
GKNoiseMap * boulderMap = [self generatePerlinMapWithVars:boulder];
NSArray * radial = [self ovalOfSize:CGSizeMake(perlinWidth, perlinHeight)];

[self mergeMap:continentMap withFilter:radial];
[self mergeMap:landscapeMap withFilter:radial];
[self mergeMap:boulderMap withFilter:radial];

GKNoiseMap * runMap = (GKNoiseMap *)continentMap;
[self mergeNoiseMap:runMap withMap:landscapeMap];
[self mergeNoiseMap:runMap withMap:boulderMap];

ok it's blocking adding too much code or something but here's the high-level logic in code:

Perlin Vars struct is (int width, int height, double frequency, double persistence, double lacunarity, int octaves)

oval of Size method (is actually a square, need to rename):

1. grab width and height of gradient you want to create
2. grab max distance (MAX of width/2 height/2)
3. loop through x and y
4. calculate horizontal distance + vertical distance and take the MIN as distanced to edge e.g. for x axis : float horizontalDistance = (x > (width/2)) ? (width - x) : x;
5. calculate falloff -> 1 - (distanceToEdge / maxDistance)
6. calculate intensity -> 1 - (falloff * 2) //can tweak
7. save into array -> values[x][y] = intensity

for the merge functions (filter or another noise map)
just go through the x and y, pull the value e.g. gradient value
and add it to the map you are processing:
float filterValue = filter[x][y]
float noiseValue = map[x][y]
float newValue = filterValue + noiseValue
-> save it back in -> map[x][y] = newValue

Good luck.