Wikipedia:Graphics Lab/Resources/QGIS/Reprojection

 —Contribute to this tutorial by completing one section welcome !

Projection (0%)

 In progress

• Raster layer to Robinson

Work for both ETOPO1 (world file), small SRTM tile, and merged tiles.

Source projection

First, you have to find the definition of your source projection/file. It's a kind of long equation which definite the properties of each projection. So:

QGis (1.7) > (double click on the layer to reproject) > Layer's properties (window pop up) > tab 'Coordinates Reference System (CRS)' > Layer Spatial Reference System : [projection's definition] > (copy it)

 In progress Which new projection for my map ?

Secondly, you have to choice your target projection.

 In progressTarget projection

Third, you have to find the definition of this target projection.

QGis (1.7) > File > Project's properties (a window pop up) > tab 'Coordinates Reference System (CRS)'

>> Select your target projection* > copy the definition (the long equation) >

>> ?create a personalized projection.?

QGis (1.7) > Raster > Warp (reproject) > (a window pop up)

> fill the fields witht he source SRS, and the target SRS > open in canvas > run > get the result.

Reproject a raster layer

Reproject a vector layer

Raster to Vector (polygons) (0%)

 In progress→ Yug

• Covert to vector
• Edit polygons
• Gdal_contour (fr)
• Using TheGIMP (fr)

Concept: Use an elevation GIS file, a discrete black & white colormap, and the Print composer to output one 1500px/1500px black & white png for each altitude (0m, +200m, +500m, etc, name the png accordingly!). This by a cycle such as 1. editing the map color, 2. actualizing the Print composer, 3. outputting the new png. Then use Inkscape to vectorize : load all png, align them, vectorize each using 2 colors + delete background. Color each vector polygon level (0m, 200m, ...) as need.

Introduction

QGis don't convert raster polygons into vector polygons. It does contours, but which have no fill, and thus, are not suitable.

QGis cycles

Inkscape cycles

Add a plugin (100%)

 — concept ok, screenshot welcome (Fetch python plugins' window).

Plugin in the repositories

Most plugin are in the repositories.

1. QGis > Plugins > Fetch python plugins (a window pop up)
2. > tab "Repositories" > Add 3rd party repositories > ok.
3. > tab "Plugins" > Filter: [YourKeyWord] > (if you see your plugin: click) > Install plugin

Our important plugins: Shaded relief ; SimpleSvg,

Plugin not in the repository

Extended content

:This section is about adding a plugin not available through QGis (1.7) > Plugins > Fetch plugins, and thus to install handily. We take the case of QGis SimpleSVG plugin.

1. Download the plugin > Unzip it.
2. Cut-Paste the folder in

   for Linux : in /home/YOURUSERNAME/.qgis/python/plugins/ (paste me here!)

   for Windows: somewhere in c:/documents and settings, within the QGis' python plugins folder.

3. QGis (1.7) > Plugins > Manage plugins > QGis Plugins Manager (pop up)¹ > search key word (SVG) > check the good plugin + ok
4. >> Open a/some vector layers or a project with them >
5. >> Plugins > Find your plugin: "Save as SVG" > Save as SVG > Choice your ouput place.

¹: this window also provide you the address of your plugin directory !

SimpleSVG currently save the QGis' screen as a SVG with the correct layer division. This save us a lot a energy for later Inkscape work, especially colorations.

SimpleSVG is a plugin currently under developement, Richard Duivenvoorde is looking for ideas for improvement.

Links

The table above has links to various tutorials and resources which can help in the creation of Wikipedia maps from digital georeferenced data (GIS).

== (I should read before writing) ==

Read:

1. /Didacticiel d'installation de winGRASS GIS
2. http://www.qgis.org/wiki/Users_Corner
3. En:User:Captain_Blood/GMT_Example

Travaux impressionnant:

• 
• 
  Ombre: SRTM3 v.2 + en:3DEM
• 
• 
  Geocoded File:China edcp location map.svg, part of the +500 Location maps.
• 
  Geocoded File:China edcp relief location map.jpg (with paralleles and lattitudes)