Python: Surface Plot not Representing Data Set Properly

Question

I am currently trying to create a 3D surface plot based on some topographic survey data I took. The data consists of a GPS position based in UTM. I then created a mesh, interpolated using the nearest neighbor method, and plotted the surface using plotly. My main problem comes from the fact that my surface plot is very spiky, whereas the scatter plot of just the raw points looks more like what I want. For reference this is topographic data of 4 dunes on a beach.

I think I have narrowed the problem down to the interpolation method, but I just don't know how to fix it so that the graph will be more smooth.

Thanks in advance for any advice/ suggestions.

import numpy as np
import plotly.graph_objects as go
import pandas as pd
from scipy.interpolate import griddata

# Read Data
eBAD = pd.read_csv('EastBeachAllDunes20190202.txt', header = None, delimiter = ',')
eBAD.columns = ["Point #","Northing","Easting","Zed","NaN"]
eBAD = pd.DataFrame(data = eBAD)

# Define Variables
x = np.array(eBAD.Easting)
y = np.array(eBAD.Northing)
z = np.array(eBAD.Zed)

# Creating Mesh
xi = np.linspace(min(x), max(x))
yi = np.linspace(min(y), max(y))
X, Y = np.meshgrid(xi, yi)
Z = griddata((x, y), z, (xi[None,:], yi[:,None]), method='nearest')

# Plot Scatter of Raw GPS Data 
fig = go.Figure(data=[go.Scatter3d(x=x, y=y, z=z,mode='markers')])
#fig.update_layout(scene_aspectmode='data')
fig.update_layout(scene_aspectmode='manual',
                  scene_aspectratio=dict(x = 5, y = 5, z = 0.5))
fig.show()

# Plot Surface Using Mesh
fig2 = go.Figure(data=[go.Surface(x = xi, y = yi, z=Z)])
#fig2.update_layout(scene_aspectmode='data')
fig2.update_layout(scene_aspectmode='manual',
                  scene_aspectratio=dict(x = 5, y = 5, z = 0.5))
fig2.show()

# Plot Surface Using Mesh
fig3 = go.Figure(data=[go.Surface(x = xi, y = yi, z=Z),go.Scatter3d(x=x, y=y, z=z,mode='markers')])
#fig2.update_layout(scene_aspectmode='data')
fig3.update_layout(scene_aspectmode='manual',
                  scene_aspectratio=dict(x = 5, y = 5, z = 0.5))
fig3.show()

Scatter Plot

Surface Plot

Scatter Plot Over Surface Plot. Here you can see that the higher points do not create a good surface visualization.