ArcGIS应用（十九）Arcgis 统计分析计算多波段图像最大值、最小值、平均值等

1.计算目的

计算多波段图像中，每个象元对应位置的所有波段值的最大值，最小值平均值等参数信息。

使用场景，比如计算时间序列遥感指数的最大值。假如有三个时间的NDVI指数，我们需要计算三个时间的最大值图像，就需要这样计算每个象元位置三个时相的最大值。

2.实现方法

2.1 使用工具

使用Arcgis统计分析工具计算得到，打开工具箱：

打开Spatial Analyst Tools中的zonal工具：

如下图：

 使用ZonalStatistics工具进行统计分析.点击该工具，界面如下：

 参数说明（原版英文说明）：

Input raster or feature zone data

Dataset that defines the zones. 这个参数用于定义统计区域，我们通常可以选择行政区域进行统计，这里我们选择需要统计的原图像，即统计原图像范围内极值等信息。

The zones can be defined by an integer raster or a feature layer.

Zone field

Field that holds the values that define each zone.

It can be an integer or a string field of the zone dataset.

Input value raster

Raster that contains the values on which to calculate a statistic. 

Output raster

The output zonal statistics raster.

Statistics type (optional)

Statistic type to be calculated.

• MEAN — Calculates the average of all cells in the value raster that belong to the same zone as the output cell.
• MAJORITY — Determines the value that occurs most often of all cells in the value raster that belong to the same zone as the output cell.
• MAXIMUM — Determines the largest value of all cells in the value raster that belong to the same zone as the output cell.
• MEDIAN — Determines the median value of all cells in the value raster that belong to the same zone as the output cell.
• MINIMUM — Determines the smallest value of all cells in the value raster that belong to the same zone as the output cell.
• MINORITY — Determines the value that occurs least often of all cells in the value raster that belong to the same zone as the output cell.
• RANGE — Calculates the difference between the largest and smallest value of all cells in the value raster that belong to the same zone as the output cell.
• STD — Calculates the standard deviation of all cells in the value raster that belong to the same zone as the output cell.
• SUM — Calculates the total value of all cells in the value raster that belong to the same zone as the output cell.
• VARIETY — Calculates the number of unique values for all cells in the value raster that belong to the same zone as the output cell.

Ignore NoData in calculations (optional)

Denotes whether NoData values in the Value input will influence the results of the zone that they fall within.

• Checked—Within any particular zone, only cells that have a value in the input Value raster will be used in determining the output value for that zone. NoData cells in the Value raster will be ignored in the statistic calculation.
• Unchecked—Within any particular zone, if any NoData cells exist in the Value raster it is deemed that there is insufficient information to perform statistical calculations for all the cells in that zone; therefore, the entire zone will receive the NoData value on the output raster.

2.2 参数设置与计算

打开图像数据， 在工具面板相关选项选择输入参数信息：

Zone Field这里默认Value会报错，目前还没找到具体原因.

 报错：

ERROR 010123: Could not get field name.
Failed to execute (ZonalStatistics).
Failed at Sun May 29 22:50:41 2022 (Elapsed Time: 0.06 seconds)

 将改选项改为count重新计算，可以得到计算结果（原图和结果图），结果图为单波段图像：

 3.结果分析

使用Identity工具查看象元属性发现，所计算结果只计算得到了前三个波段的最大值，而不是所有波段的最大值。这是这个工具的局限所在，可能和软件版本有关，以前版本针对raster数据计算也是只能计算前三个波段。后面将进一步分析原因。