Projection: Difference between revisions

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= Support Material =
= Support Material =
* Vector data: have enough vertices in your vector data: [[File:V proj result.png|300px|center|thumb|Results in EU LAEA (EPSG: 3035)]]
* Ready to use .PRJ files (in the usual WKT format) as used by recent versions of ESRI ArcView: [http://esri-germany.de/downloads/software/Koordinatensysteme.zip download]
* Ready to use .PRJ files (in the usual WKT format) as used by recent versions of ESRI ArcView: [http://esri-germany.de/downloads/software/Koordinatensysteme.zip download]


= Important: have enough vertices in your vector data =
= See also =


When reprojecting vector data, it is important to have enough vertices in the data.
View Map Projections
* http://map-projections.net/singleview.php
* [http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.html Cartographical Map Projections] by Carlos A. Furuti


Example: Box (polygon) created with {{cmd|v.in.region}}:
Lists
* [http://www.epsg.org/Geodetic.html EPSG Geodetic Parameter Dataset]
* [http://www.asprs.org/resources/grids/ ASPRS Grids and Datum]
* Catalog of projections: http://proj4.org/projections
* [http://www.remotesensing.org/geotiff/proj_list/ Projections Transform List (PROJ4)]
* [http://www.mapref.org/ MapRef - The Collection of Map Projections and Reference Systems for Europe]
* [http://www.crs-geo.eu Information and Service System for European Coordinate Reference Systems - CRS]


[[Image:V proj input unsplit boundaries.png|300px|center|thumb|4 corner rectangle, LatLong (no further vertices)]]<br>
Related to Germany:
* http://support.esri-germany.de/files/support/KoordinatensystemeInDeutschland.pdf
* http://support.esri-germany.de/files/support/KoordinatensystemeNachbarnDeutschlands.pdf
* http://support.esri-germany.de/files/support/KoordinatensystemeWeltweit.pdf


v.split -n box output=box_w_vertices length=200 units=kilometers
Related to Austria:
[[File:V proj input split boundaries.png|300px|center|thumb|Split rectangle, LatLong]]<br>
* [http://www.alectoria.at/content/view/17/1/ Projection parameters of Austria]


As obvious from the results, enough vertices must be present in the map to avoid (severe) distortion. Note that this applies likewise to "ogr2ogr" and QGIS:
== Google Map Projection ==
[[File:V proj result.png|300px|center|thumb|Results in EU LAEA (EPSG: 3035)]]<br>


= See also =
Also called "pseudo-mercator" - note that there are many issues with this projection! Handle with care.
* In English:
** [http://www.epsg.org/Geodetic.html EPSG Geodetic Parameter Dataset]
** [http://www.asprs.org/resources/grids/ ASPRS Grids and Datum]
** [http://www.remotesensing.org/geotiff/proj_list/ Projections Transform List (PROJ4)]
** [http://www.mapref.org/ MapRef - The Collection of Map Projections and Reference Systems for Europe]
** [http://www.crs-geo.eu Information and Service System for European Coordinate Reference Systems - CRS]
*  In German language:
** http://support.esri-germany.de/files/support/KoordinatensystemeInDeutschland.pdf
** http://support.esri-germany.de/files/support/KoordinatensystemeNachbarnDeutschlands.pdf
** http://support.esri-germany.de/files/support/KoordinatensystemeWeltweit.pdf
** [http://www.alectoria.at/content/view/17/1/ Projection parameters of Austria]


== Google Map Projection ==
* http://www.sharpgis.net/2007/07/27/TheMicrosoftLiveMapsAndGoogleMapsProjection.aspx
* http://www.sharpgis.net/2007/07/27/TheMicrosoftLiveMapsAndGoogleMapsProjection.aspx
* http://cfis.savagexi.com/articles/2006/05/03/google-maps-deconstructed
* http://cfis.savagexi.com/articles/2006/05/03/google-maps-deconstructed


[[Category: FAQ]]
[[Category: FAQ]]

Revision as of 09:45, 21 June 2017

Projections and Datum Transformations

Brief introduction to projections and spatial transformations in GRASS

A GRASS location is referenced with a single projection and coordinate system (or unreferenced as XY location). When creating a new location from an existing raster or vector map using the tools available from the startup screen or the map import commands, projection and coordinate system are defined. To change the projection of maps, a new location has to be created and the desired maps have to be reprojected into it from the source location as explained below.

Read on in projectionintro...

Creation of a GRASS location

Support Material

  • Vector data: have enough vertices in your vector data:
    Results in EU LAEA (EPSG: 3035)
  • Ready to use .PRJ files (in the usual WKT format) as used by recent versions of ESRI ArcView: download

See also

View Map Projections

Lists

Related to Germany:

Related to Austria:

Google Map Projection

Also called "pseudo-mercator" - note that there are many issues with this projection! Handle with care.