Measurements of Classes

A thematic information layer can have the raster and vector representation. After digitizing the data from a thematic information layer (points, lines and polygons), the user can transform the vector representation into a raster representation, and have both representations in the same IL.

Eventually, it is possible to get a thematic information layer only with a resulting raster representation, for instance, by crossing information from two IL's or from digital image classifications. This thematic IL can also be converted from the raster representation to the vector representation. See about the format transformation ( raster to vector and vector to raster).

The measurements of classes report presents the area and length values when using the vector representation, and only the area values when using the raster representation (thematic image), both in square kilometers.

The area value is presented for each class , the classes total, the total of not classified polygons and the active thematic IL total area. If the IL has both representations, that is raster and vector, it is possible to get a report for both for comparison purpose. The classes length value will only be presented when there are vector lines associated to thematic classes.

Computing Measurements of Classes:

  • activate using the "Control Panel" the thematic information layer used for the computation;
  • select in the main menu Thematic - Measurements of Classes...;
  • click the Thematic Image button and/or Vector Map. If the active IL has both representations, both buttons will be available;
  • click on Apply. The report is presented in the window's central part. The area report shows:
    • IL name,
    • representation type,
    • area values by class,
    • classes total area,
    • total area of the non classified polygons (vector case), and information layer total area.
    The length report (only for the associated classes) shows:
    • IL name,
    • length value by class,
    • classes total length, and
    • total length for the non classified lines.
  • click on Save... to store the displayed report as a text file. The "Save As" window is presented. Type a name and click on Save.
  • click on Export Worksheet... to store the report in a spreadsheet format in a text file (ASCII). The Save As window is displayed. Select or Change the name and click on Save.
  • The suggested name corresponds to the category that generates the second column (CATEG_<categoryname> ) ;
  • if the file already exists, the "substitution" will happens as follows: the previous file will be kept with a new name (<filename>_OLD.txt), the new file will be created with all lines from the old file, plus all the new lines, and the classes consistency will be kept (new classes will generate new columns);
  • the spreadsheet is cumulative and can be imported from an "EXCEL" file to compute the classes area summation from several projects;
  • exported spreadsheet via "Cross Tabulation" can be used to accumulate"Measurement of Classes" data and vice-versa;
  • column delimitation = semi-colon character (;)
  • numerical data : decimal separator = dot character (.) and thousands separator = none (non-existent)

See the example below:

PROJETO;CATEG_Cartatema;PI;WRSTM;UF;DATA;UNID;REPRES;T_PI;T_CLASSES;T_NAOCLASSIF;
TC_CATEG;TC_PI;T_BACKGROUND;classe1;classe2;...
P02_047_00565_300702;Cartatema;classif;00565;AM;300702;(kmxkm);repres_matriz;
49777.02;26797.37;22979.64; ; ;111.11;222.22;...
P02_054_22062_020902;Cartatema1;classif_final;22062;MA;020902;(kmxkm);repres_matriz;
49777.02;1243.62;48533.40; ; ;333.33;444.44;...


NOTE:
Click on Erase to clean the data presented in the window.

See also:
LEGAL Programming
Database Query.

Other geographic analysis options in the Spring