我试图用matplotlib将两个.tiffs可视化为3D曲面图。结果看起来有点奇怪-有人能帮助我吗？

# import relevant moduls
from osgeo import gdal
import numpy as np
import matplotlib.pyplot as plt

# Specify input files
dem_old = '../data/Nisqually_1987.tif'
dem_new = '../data/Nisqually_2017.tif'

# Creating first 3D figure
# set up a figure twice as wide as it is tall
fig = plt.figure(figsize=plt.figaspect(0.5))

# Old DEM plot
ax = fig.add_subplot(1, 2, 1, projection='3d')
dem = gdal.Open(dem_old)
dem_array = dem.ReadAsArray()

lin_x = np.linspace(0,1,dem_array.shape[0],endpoint=False)
lin_y = np.linspace(0,1,dem_array.shape[1],endpoint=False)
y,x = np.meshgrid(lin_y,lin_x)
z = dem_array
surf = ax.plot_surface(x,y,z,cmap='terrain', edgecolor='none')
fig.colorbar(surf, shrink=0.5, aspect=15)
ax.set_title('3D Nisqually-Gletscher Oberfläche (1987)')
plt.xticks([])
plt.yticks([])

# New DEM 3D plot
ax = fig.add_subplot(1, 2, 2, projection='3d')
dem_2 = gdal.Open(dem_new)
dem_array_2 = dem_2.ReadAsArray()

lin_x_2 = np.linspace(0,1,dem_array_2.shape[0],endpoint=False)
lin_y_2 = np.linspace(0,1,dem_array_2.shape[1],endpoint=False)
y,x = np.meshgrid(lin_y_2,lin_x_2)
z = dem_array_2
surf = ax.plot_surface(x,y,z,cmap='terrain', edgecolor='none')
fig.colorbar(surf, shrink=0.5, aspect=10)
ax.set_title('3D Nisqually-Gletscher Oberfläche (2017)')
plt.xticks([])
plt.yticks([])

# show plot
plt.savefig ('glaciers_3D.png')
plt.show()

数据来自：https://www.sciencebase.gov/catalog/item/6140d0a3d34e1449c5d6000a