Surface water monitoring method and apparatus, computer device, and storage medium
What disclosed are a surface water monitoring method and apparatus, a computer device, and a storage medium. The method includes: obtaining optical satellite images and synthetic aperture radar satellite images of an area to be monitored in a preset time period; determining a first target region in each optical satellite image, determining a water body type of a pixel in a second target region in the SAR satellite image corresponding to the first target region; determining water body types of pixels in other regions in the optical satellite image, the other regions being regions in the optical satellite image other than the first target region; and determining surface water distribution information of the area to be monitored in the preset time period according to the water body type of the pixel in the second target region and the water body types of the pixels in the other regions.
1 . A surface water monitoring apparatus, comprising:
an acquisition module configured to obtain optical satellite images and SAR satellite images of an area to be monitored in a preset time period;
a first determination module configured to determine a first target region in each optical satellite image, the first target region being a region in the optical satellite image, where pixels, whose observation data volume is less than or equal to a preset data volume, is located;
a second determination module configured to determine a water body type of a pixel in a second target region in the SAR satellite image corresponding to the first target region as being either a water body type or non-water body type;
a third determination module configured to determine water body types of pixels in other regions in the optical satellite image, the other regions being regions in the optical satellite image other than the first target region; and
a fourth determination module configured to determine surface water distribution information of the area to be monitored in the preset time period according to the water body type of the pixel in the second target region and the water body types of the pixels in the other regions.
2 . The surface water monitoring apparatus of claim 1 , wherein the second determination module comprises:
a first determination unit configured to obtain a backscatter coefficient corresponding to the pixel in the second target region; and
a second determination unit configured to determine the water body type of the pixel in the second target region according to the backscatter coefficient corresponding to the pixel in the second target region.
3 . The surface water monitoring apparatus of claim 2 , wherein the second determination unit is further configured to determine the water body type of the pixel with the backscatter coefficient greater than or equal to a first preset threshold to be a non-water body pixel type if the backscatter coefficient corresponding to the pixel in the second target region is greater than or equal to the first preset threshold.
4 . The surface water monitoring apparatus of claim 3 , wherein the second determination unit is further configured to:
obtain historical water body types of the pixel with the backscatter coefficient less than the first preset threshold in a plurality of historical time periods if the backscatter coefficient corresponding to the pixel in the second target region is less than the first preset threshold; and
determine the water body type of the pixel in the second target region with the backscatter coefficient less than the first preset threshold according to the historical water body types of the pixel with the backscatter coefficient less than the first preset threshold in the plurality of historical time periods.
5 . The surface water monitoring apparatus of claim 4 , wherein the second determination unit is further configured to:
determine the water body type of the pixel with the backscatter coefficient less than the first preset threshold in the second target region to be a water body pixel type if a proportion of the water body pixel types among the historical water body types of the pixel with the backscatter coefficient less than the first preset threshold is greater than a second preset threshold; and
determine the water body type of the pixel with the backscatter coefficient less than the first preset threshold in the second target region to be the non-water body pixel type if the proportion of the water body pixel types among the historical water body types of the pixel with the backscatter coefficient less than the first preset threshold is less than or equal to the second preset threshold.
6 . The surface water monitoring apparatus of claim 1 , wherein the third determination module comprises:
an acquisition unit configured to obtain historical water body types of pixels in third target regions in optical satellite images in a plurality of historical time periods, wherein each third target region is at least one of a snow-covered region and a mountain-covered region among the other regions;
a third determination unit configured to determine a water body type of the pixel in each third target region according to the historical water body types of the pixels in the third target regions in the plurality of historical time periods;
a fourth determination unit configured to determine a new water detection index (WDI) of a pixel in a fourth target region according to a geometric linear discrimination analysis (GLDA) algorithm and reflectance of a top layer of atmosphere of each wave band corresponding to the pixel in the fourth target region; and
a fifth determination unit configured to determine a water body type of the pixel in the fourth target region according to the new WDI of the pixel in the fourth target region, the fourth target region being a region other than the third target region among the other regions.
7 . The surface water monitoring apparatus of claim 6 , wherein the third determination unit is configured to:
determine the water body type of the pixel corresponding to a proportion of water body pixel types among the historical water body types of the pixel in the third target region greater than the second preset threshold to be a water body pixel type, if the proportion is greater than the second preset threshold; and
determine the water body type of the pixel corresponding to the proportion less than or equal to the second preset threshold to be a non-water body pixel type if the proportion of the water body pixel type in the historical water body types of the pixel in the third target region is less than or equal to the second preset threshold.
8 . The surface water monitoring apparatus of claim 6 , wherein the fifth determination unit is further configured to:
determine the water body type of the pixel with the new WDI greater than a third preset threshold to be a water body pixel type, if the new WDI of the pixel in the fourth target region is greater than the third preset threshold; and
determine the water body type of the pixel with the new WDI less than or equal to the third preset threshold as a non-water body pixel type, if the new WDI of the pixel in the fourth target region is less than or equal to the third preset threshold.
9 . The surface water monitoring apparatus of claim 8 , wherein optical satellites are the same kind of satellites, the water body type of the pixel with the new WDI greater than the third preset threshold is determined to be the water body pixel type, and the water body type of the pixel with the new WDI less than or equal to the third preset threshold is determined to be the non-water body pixel type.
10 . The surface water monitoring apparatus of claim 8 , wherein optical satellites comprise at least two kinds of satellites, the water body type of the pixel in the fourth target region is determined to be the water body pixel type if the water body type of the pixel in the fourth target region in an image of any one kind of optical satellite image is the water body pixel type, and the water body type of the pixel in the fourth target region is determined to be the non-water body pixel type, if the water body types of the pixels in the fourth target regions in all optical satellite images are the non-water body pixel types.
11 . The surface water monitoring apparatus of claim 8 , wherein the third preset threshold is set to be 0.06.
12 . The surface water monitoring apparatus of claim 6 , wherein the new WDI is calculated by:
W
D
I
=
β
T
x
wherein
β
=
[
-
0
.
1
7
1
,
0
.
6
74
,
-
0.534
,
-
0.252
,
-
0.055
,
0
.
3
58
,
-
0.03
,
0
.
2
0
7
]
T
and
x
=
[
B
,
G
,
R
,
NIR
,
S
WIR
1
,
S
WIR
2
,
NDWI
,
MNDWI
]
T
wherein B denotes the reflectance of the top layer of the atmosphere corresponding to a blue wave band, G denotes a reflectance of the top layer of the atmosphere corresponding to a green wave band, R denotes a reflectance of the top layer of the atmosphere corresponding to a red wave band, NDWI denotes a normalized difference water index, MNDWI denotes a modified normalized difference water index, NIR denotes a reflectance of the top layer of the atmosphere of a near-infrared wave band, SWIR 1 denotes a reflectance of the top layer of the atmosphere of a short-wave near-infrared wave band 1 , and SWIR 2 denotes a reflectance of the top layer of the atmosphere of a short-wave near-infrared wave band 2 .
13 . The surface water monitoring apparatus of claim 3 , wherein the first preset threshold is determined according to an expectation maximization algorithm and the backscatter coefficient corresponding to the pixel in the second target region.
14 . The surface water monitoring apparatus of claim 4 , wherein the historical water body types of the pixel with the backscatter coefficient less than the first preset threshold in the plurality of historical time periods are calculated according to observation data corresponding to each pixel in the optical satellite images in the plurality of historical time periods.
15 . The surface water monitoring apparatus of claim 6 , wherein a duration of one historical time period is the same as a duration of the preset time period.