Ground shadows look inaccurate and muddy

I have made a Threejs project, where I dynamically create a ground from perlin noise. Here is the code:

createGround() {

const resolutionX = 100
const resolutionY = 100
const actualResolutionX = resolutionX + 1 // plane adds one vertex
const actualResolutionY = resolutionY + 1


const geometryPlane = new THREE.PlaneGeometry(this.sizeX, this.sizeY, resolutionX, resolutionY)

const noise = perlin.generatePerlinNoise(actualResolutionX, actualResolutionY)

let i = 0

for (let x = 0; x < actualResolutionX; x++) {
  for (let y = 0; y < actualResolutionY; y++) {
    let h = noise[i]
    }

    geometryPlane.vertices[i].z = h
    i++
  }
}

geometryPlane.verticesNeedUpdate = true
geometryPlane.computeFaceNormals()

const materialPlane = new THREE.MeshStandardMaterial({
  color: 0xffff00,
  side: THREE.FrontSide,
  roughness: 1,
  metallness: 0,
})

const ground = new THREE.Mesh(geometryPlane, materialPlane)
geometryPlane.computeVertexNormals()
ground.name = GROUND_NAME
ground.receiveShadow = true
scene.add(ground)

}

I am happy with the geometry that is generated, but the problem is the shadows look really inaccurate.

Here is my code for the light:

const light = new THREE.DirectionalLight(
  'white',
  1,

)
light.castShadow = true
light.position.set(100, 100, 100)
scene.add(light)

light.shadowCameraVisible = true

My question is, how can I make the grounds shadow look more accuarate and defined, and show off the grounds geometry?

from Ground shadows look inaccurate and muddy