• TestTop: Test for topologically structured files

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Access the application from the menu: "Edition | Build topology | Test topology"

Presentation and options

This program carries out some consistency tests on topologically structured files. The following tests are currently available:

Polygon neighbourhood test.: Checks that no two polygons with the same thematic attributes fall on either side of the same arc. A BADLINES.VEC (points) file is generated that marks with 3 points the lines that present erroneous neighbours, and a QUEIXESL.TXT file that describes the errors. It also checks for the presence of empty records beside records with data, reported in the BADLINIC.VEC and QUEIXLIC.TXT files. These checks are carried out for all thematic fields simultaneously.

Polygon file coherence test.: A polygon file contains two files with partially redundant contents. On the one hand there is a table that indicates, for each arc of the polygon, what is to the right and to the left of that arc; on the other hand there is also a table that indicates, for each polygon, what is the sequence of arcs that defines it. This test explores the redundant information and looks for possible incoherence. If differences are found the program suggests an automatic solution consisting in rewriting the first table based on the information in the second. If the polygon file has been obtained from a program such as Ciclar, this test should never find any inconsistencies.

Arc and node file coherence test.: An arc file contains a table indicating, for each arc, which are the initial and final nodes. A node file contains a table indicating, for each node, what sort of node it is and which arcs meet at that node. These two sets of information are partially redundant. This test looks at this redundant information and checks for possible inconsistencies. If differences are found the program suggests automatic solutions that consist in recreating the node file completely based on the information in the arc file. Given that this simultaneously modifies the content of the nodes data base, the link between the graphical elements and the alphanumeric attributes will be lost. If the program only finds incoherence in the type of node indicated in the node file, the program can reconstruct the node file without danger of loosing the information. If the arc file and the node file have both been obtained from the LinArc program then this test should never find any inconsistencies.

Test for the need for lengths, perimeters and elipsoidal areas.: When the cartographic projection is known (see list of known projections in the help for the CANVIPRJ program), it is advisable to include in the data base the fields LONG_ARCE, PERIMETREE and AREAE, to indicate the real length, perimeter and area of each object, calculated on the terrestrial elipsoid with precise geodesic criteria. These fields are especially appropriate for map projections for which calculations on the map give values that are clearly different from the real values calculated on the Earth's surface (Mercator, for example) or for maps with projections where the differences may be small but which include long lines that can acummulate significant errors. In the cases where the program determines that it is possible to make geodesic calculations, it adds the above mentioned fields to the data base. Depending on the map projection used, the program declares these new fields visible, according to the most commonly used measure of length, perimeter and area for that projection. These visibility criteria can be changed in the REL file.

Test of coherency between values from geometrical-topological fields: Test of coherency between values from geometrical-topological fields from the main database table and binary file (arcs only).

Dialog box of the application

TestTop dialog box