# Hugo Ledoux

associate-prof in 3D geoinformation at TU Delft
blog

# FieldGML

FieldGML is a GML-based representation for fields in 2D and 3D, one that permits us to represent efficiently not only rasters, but also fields in other forms. It is my attempt at improving ISO19123, the standard for coverages.

FieldGML is based on current standards, is flexible, extensible and is also more appropriate than raster structures to model the kind of datasets found in GIS-related applications. To know more FieldGML, you can read either of these documents:

Representing Continuous Geographical Phenomena with FieldGML. This is the final report of the project during which it was developed. It contains details about the GML application schema, and there are some examples of files.

FieldGML: an alternative representation for fields. Hugo Ledoux. In Anne Ruas and Christopher M. Gold (eds.), Headway in Spatial Data Handling, Lecture Notes in Geoinformation and Cartography, Springer, 2008, pp. 385–400.

@incollection{_08sdh,
author = {Ledoux, Hugo},
title = {FieldGML: An Alternative Representation for Fields},
booktitle = {Headway in Spatial Data Handling},
publisher = {Springer},
year = {2008},
editor = {Ruas, Anne and Gold, Christopher M.},
series = {Lecture Notes in Geoinformation and Cartography},
pages = {385--400}
}

## GML application schema

The application schema fieldgml.xsd
The documentation of the schema without the GML types.
The long documentation of the schema with all the GML types.

## Examples of FieldGML files

5k_pts.xml is a file with 5000 scattered points, representing the elevation of a region. The interpolation method defined in this file is natural neighbour interpolation.

5k_tess.xml contains the same 5000 points, but here these are stored in a TessPointsRule of type “Delaunay”, which means that a Delaunay TIN has to be created to interpolate. The interpolation method is based on the tessellation, and inside each triangle a linear function is used.

contours.xml contains contour lines representation the same terrain as the 2 previous examples. The interpolation method defined here is inverse-distance to a power, with a search radius of 12 units.

array2d.xml is a FieldGML file pointing to a GTiff file array2d.tif. The file is the result of creating a raster of the 5000 scattered points above (5k_pts.xml). The interpolation method defined here is piecewise constant, that is the value estimated at location (x,y) is the value of the pixel at that location.

geology3d.xml contains 150 points scattered in 3D space. The interpolation method defined in this file is natural neighbour interpolation.