Differences

This shows you the differences between two versions of the page.

--- calc_areas [2013/07/10 17:05]
admin [Output]
+++ calc_areas [2025/07/19 03:04] (current)
admin [Notes]
@@ Line 8: / Line 8: @@
 ^ Name  ^ Type  ^ Description  ^
-| Categorical Map  | [[Categorical Map Type|Categorical Map]]  | Map containing classes or categories.  |
+| Source  | [[Categorical Map Type|Categorical Map]]  | Map whose non-null cells correspond to categories or classes.  |
+| Use Authalic Area  | [[Boolean Value Type|Boolean Value]]  | If set to true, the area of each cell in a geographic grid (Lat/Long) is computed using an authalic sphere, which preserves surface area during projection. This improves the accuracy of area calculations across all latitudes by avoiding distortions in geographic coordinate systems. If the grid is geographic but the flag is set to false, all cells are treated as having the same area, calculated by treating the length of one degree of latitude or longitude as a constant 111255 meters.  |
 ===== Output =====
@@ Line 23: / Line 23: @@
 Only the areas corresponding to class or categories defined in the input map header are calculated.
-If the cell dimensions are represented using degrees, the areas in hectares and square meters becomes an approximation. All cells are always supposed to be of the same size.
+The table containing the resulting area has the following format.
+^ Column Name  ^ Key or Data?  ^ Column Type  ^ Description  ^
+| "Category"  | Key  | Real  | Category in the feature map  |
+| "Area_In_Cells"  | Data  | Real  | Area of corresponding category in cells  |
+| "Area_In_Hectares"  | Data  | Real  | Area of corresponding category in hectares  |
+| "Area_In_Square_Meters"  | Data  | Real  | Area of corresponding category in square meters  |
 ===== Internal Name =====
 CalcAreas