Find Extremum Value

Instructions for use

The Find Extremum Value function is used to find the extreme points (including the highest point and the lowest point) of certain areas on the Raster Dataset, and determine the position and extreme value information of these extreme points. Application provides two ways to determine the search region range, one is to select Zonal Data to search, and the other is to Draw Region on Raster Data as the search range.

Region Find Extremum Value

Function Entry

  • Spatial Analysis tab-> Raster Analysis group-> Surface Analysis-> Region Find Extremum Value.
  • Toolbox-> Raster Analysis-> Surface Analysis-> Terrain Calculation-> Region Find Extremum Value. (iDesktopX)

Parameter Description

  • Raster Data: Set the Raster Data to be found, including the Datasource and Raster Dataset where the Raster Data is located.
  • Zonal Data: Select Zonal Data, Datasource where Zonal Data is located, and Dataset.
  • Parameter Settings: Set the parameters of the Find Extremum Value, including the maximum number of extreme points and the minimum number of extreme points in the area to be searched. The default maximum and minimum extreme points are both 256.
  • Result Data: Statistics Result will be saved as a 3D Point Dataset. The Dataset's Property Field stores the extreme point elevation information and the extreme point type, that is, whether it is a maximum value or a minimum value.
  • After the operation is completed, it will automatically mark the highest point in the drawn region with red highlight and mark the lowest point in the Draw Region with blue highlight in the Current Map, and the Output Window will output the information of the found extreme points, including the number of extreme points and the corresponding extreme values. Note: When the entire Zonal Data is looked up, the extreme point information is not output. Press Esc to clear the highlighted extreme points.

Draw Region lookup

Function Entry

  • Spatial Analysis tab-> Raster Analysis group-> Surface Analysis-> Draw Polygon Find Extremum Value.

Operating Instructions

  • A prompt pops up in the Output Window, "Please use the mouse to draw the area you want to count on the map, and then click the right button to count.". Follow the prompts to draw a temporary polygon as the statistics area. See Draw Polygon for how to draw polygons .
  • After drawing, the Find Extremum Value "dialog box pops up in Map.
  • Set Find Extremum Value parameters, including the maximum and minimum number of extreme points to be found. The default statistics have a maximum/minimum number of extreme points of 256.
  • Set Result Data to save the search result as a 3D Point Dataset. The Property Field of the Dataset will store the elevation information of the extreme value point obtained by statistics and the type of the extreme value point, that is, the maximum value (Max) or the minimum value (Min).
  • After the operation is completed, it will automatically highlight the highest point in the drawn region in red and the lowest point in the Draw Region in blue in Current Map, and the Output Window will output the extreme point information obtained from the statistics, including the number of extreme points and the corresponding extreme values. Press Esc to clear the temporary area of the plot and highlight the extreme points.

Remark

Zonal Statistics and Find Extremum Value are both aimed at regional statistics, and there are both similarities and differences between them.

  • Zonal Statistics refers to the statistics of Raster Data (value data) within the area range (Zonal Data, which can be Vector Data or Raster Data). Divide Raster Data according to Zonal Data, and count Raster Data covered by each area. Statistic Infomations include mean, standard deviation, sum, category, range, mode, minimum, and median. Statistics Result gets a Raster Dataset and a Tabular Dataset.
  • Find Extremum Value is used to find the extreme points (the maximum extreme point and the minimum extreme point) of the pixels within the Zonal Data range on the Raster Dataset, and determine the positions and extreme information of these extreme points. Zonal Data can be formulated by means of Select Region object and Draw Region. The result of the Find Extremum Value will generate a 3D Point Dataset. The height information of the found extreme point and the type of the extreme point (maximum value or minimum value) will be saved in the Property Field of the Dataset.