Support
Decimal precision when exporting the plots GML (area, displacement and IVGA reports)
Summary
When preparing plots for the Spanish Cadastre with MDT and generating the GML file, several common problems have their origin in the precision with which the coordinates of the plot polygon are exported. This article brings together the cases related to that precision: the error stating that the area does not match the geometry when uploading the GML to the Cadastre site, plots appearing displaced when they are exported and reimported, and the difficulty of obtaining "positive" IVGA reports (Informe de Validación Gráfica Alternativa, the Cadastre's alternative graphic validation report) when the Cadastre generates multiple very small plots.
Applies to
MDT — the documented cases correspond to different versions: most of them to MDT and one to MDT 25. The tickets do not record the specific version number except in that case. Also applicable to MDT 26, the current version.
MDT plot coordinate export function: GML generation and export decimals configuration.
Symptoms
When generating the GML of a plot and uploading it to the Cadastre electronic site, this error appears: "La superficie de la parcela no coincide con la superficie de la geometría proporcionada" (the plot area does not match the area of the geometry provided).
When exporting the plots for the GML files and reimporting them, they appear displaced from their original position, which causes problems with the land registry and the Cadastre.
Manually adjusting the perimeter vertices to obtain "positive" IVGA reports is tedious, and the Cadastre frequently detects errors when they are uploaded.
Cause
Area mismatch and displacement on reimport: the export of the plot polygon coordinates is configured with too few decimals (0, or 2-3 decimals), while the polyline was drawn in the CAD with 7 or 8 decimals. That loss of precision introduces inaccuracy into the exported geometry and causes the area error or the displacement when reimporting.
IVGA reports: there is no specific function for this adjustment, because the problem depends on the variable response of the Cadastre, which sometimes generates multiple very small plots.
Solution
Case: the area does not match, or the plots are displaced when reimporting the GML
Open Utilities > Configuration > Plots.
Under GML Export, increase the Number of Decimals used to export the coordinates of the plot polygon:
If the problem is the area error when uploading the GML, change the value to 3 decimals.
If the problem is the displacement when exporting and reimporting, set a higher precision, for example 5 or 6 decimals.
Generate the GML again.
If the problem continues, send the drawing to technical support for review.
Case: obtaining "positive" IVGA reports from the Cadastre
There is no specific tool for this adjustment, because the response of the Cadastre is variable and it frequently generates many very small plots. The options recommended by support are:
Download the small plots generated by the Cadastre and merge them with the program's plot tool.
As a faster alternative, calculate the outline of the plot with the CAD's own boundary tools and then use MDT.
Increase the GML export precision from Configuration > Plots (see the first case): this considerably reduces the problem.
If the problem persists
If after increasing the decimals the GML still returns the area error, or the plots are still displaced, send the drawing to APLITOP technical support so that they can reproduce the situation.
In the case of the IVGA reports, since the behaviour depends on the response of the Cadastre, contact support if the options above do not sufficiently reduce the number of tiny plots.
Category: Cadastre and GML · Level: Intermediate