Seasonal effects of impervious surface estimation in subtropical monsoon regions

Figures & data

Figure 1. The location of the study area in PR China.

Figure 2. Landsat ETM+images (R: band 5; G: band 4; B: band 3).

Table 1. Definition of the land covers used in this study.

Land use type	Definition
Water	Rivers, lakes, and seasonal water body from VSA
Vegetation	Greening areas, crops, grass, and other agricultural lands
Bare soil	Under construction land with bare soils exposed
Clouds	Small and fragmentary clouds that are difficult to remove
Shades	Topographical shades and shades from tall buildings, trees, etc
Dark impervious surfaces	Rooftops, roads, and parking lots that are made of asphalt, concrete tile, and other materials with low spectral reflectance.
Bright impervious surfaces	Cool rooftops and green rooftops that are made of cool materials, like metal, which are designed to highly reflect solar radiation

Note: Clouds and shades are treated as land covers since they have unique spectral and spatial characteristics compared with other land covers in satellite images.

Figure 3. Impervious surfaces estimation (bright: IS; dark: Non-IS)-ANN.

Table 2. Accuracy assessment of the classification results by ANN.

Date	OA (%)	Kappa	Prod.IS (%)	Prod.NIS (%)	User.IS (%)	User.NIS (%)
10 January 2009	91.4367	0.8287	89.30	93.83	94.22	88.64
2 May 2009	88.2519	0.7651	85.96	90.83	91.34	85.19
22 August 2009	84.5011	0.6873	89.57	78.80	82.61	87.04
9 October 2009	83.2979	0.6615	92.11	73.38	79.56	89.21

OA, overall accuracy; Kappa, Kappa coefficient; Prod.IS, producer accuracy of impervious surfaces; Prod.NIS, producer accuracy of nonimpervious surfaces; User.IS, user accuracy of impervious surfaces; User.NIS, user accuracy of nonimpervious surfaces.

Figure 4. Impervious surfaces estimation (bright: IS; dark: Non-IS)-SVM.

Table 3. Accuracy assessment of the classification results by SVM.

Date	OA (%)	Kappa	Prod.IS (%)	Prod.NIS (%)	User.IS (%)	User.NIS (%)
10 January 2009	92.0028	0.8394	93.05	90.83	91.94	92.07
2 May 2009	83.0149	0.6588	84.76	81.05	83.42	82.54
22 August 2009	84.9965	0.7000	82.75	87.52	88.18	81.86
9 October 2009	83.2272	0.6592	93.98	71.13	78.55	91.31

OA, overall accuracy; Kappa, Kappa coefficient; Prod.IS, producer accuracy of impervious surfaces; Prod.NIS, producer accuracy of nonimpervious surfaces; User.IS, user accuracy of impervious surfaces; User.NIS, user accuracy of nonimpervious surfaces.

Figure 5. Average digital numbers of different land-use types in humid areas.

Figure 6. Effects of seasonal changes of typical targets (yellow: impervious surfaces).

Figure 7. Comparison of the seasonal sensitivity of different methods.