# Geospatial filters

## Contents

## Introduction

The need of filters to easily switch between differents formats of vector datas.

## VectorDataToGISTableFilter

2 versions:

- Old version: Translate VectorData geometries in SQL commands (like the shp2pgsql command)
- New version: Translate VectorData using OGR driver which write datas in a PostGIS table

## GISTableToVectorDataFilter

Use the OGR driver IO translator

## LabelMapToVectorDataFilter

The algorithm follows a finite states machine described in the following paper:

*"An algorithm for the rapid computation of boundaries of run-length*
encoded regions", Francis K. H. Queck, in Pattern Recognition 33
(2000), p 1637-1649.

Lines in the RLE are first sorted in lexicographical order (to ensure ordered RLE), and the finite states machine tracks the edge following 8 canonical states given by the configuration of two consecutive raws of lines.

Iterations are done until convergence which is guaranteed to happen.

Problem in bounding regions

## VectorDataToLabelMapFilter

For now, only available for polygon translation

for line, need to create a polyline with bresenham algorithm

## LabelMapToGISTableFilter

in progress... Use the functor and a addpolygons function Need to save the label in a alphanumeric column

## GISTableToLabelMapFilter

in progress...

## LabelMapToGISTableFilter

in progress...