Wikipedia:Graphics Lab/Resources/QGIS/Get ready: Difference between revisions

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Latest revision as of 07:10, 12 October 2023

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*Your QGis projects will be saved in the ''Projects'' folder.

*''Examples'' let'slets you collect any maps on Wikipedia that you like and want to study ([[reverse engineering]]).

*''Outputs'' will host the many intermediate outputs you will generate and look at to improve your mapmaking skills, as well as any finished maps you create.

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===Topography/bathymetry===

[[file:QGis_ETOPO1_vs_SRTM3_-_quality_match.jpeg|thumb|600px|Quality comparison between ETOPO1 (pixelated) and SRTM3 (smoother) data sets. This difference doesn't matter for making large maps with coverage greater than 1000km (~620mi) across.]]

* {{GIS data for Graphic Lab |name=ETOPO1 |url_download=http://www.ngdc.noaa.gov/mgg/global/global.html |publisher=[[NGDC]]-[[NOAA]] |year=2009 |license= Public ___domain |tag= standard |url_doc=http://www.ngdc.noaa.gov/mgg/global/etopo1sources.html |layers=topography & bathymetry |precision_max=1850m (1minute arch) |covered_area= all Earth (90N-90S, landmass & sea floor) |datum=WSG WGS 84 |projection = (?) |extensions=.zip → .tif and others |size_compressed=326Mo |size_uncompressed=900Mo |tile_size=whole earth |tiles_total= 1 |comment = Perfect for very large maps (ex: > France).|editor_note= For this tutorial, download: [http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO1/data/ice_surface/grid_registered/georeferenced_tiff/ ETOPO1 Ice Surface (grid registered)] or [http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO1/data/bedrock/grid_registered/georeferenced_tiff/ ETOPO1 Bedrock (grid-registered)]. nb: ETOPO1 (1px=1km²) is a better data than ETOPO2 (1px=2kmx2km).}}

* {{GIS data for Graphic Lab |name= SRTM3 (90m) |url_download= http://demex.cr.usgs.gov/DEMEX/ |publisher= NASA / USGS |year= 2000 |license= Public Domain |tag= standard |url_doc= http://dds.cr.usgs.gov/srtm/version2_1/Documentation/SRTM_Topo.pdf |layers= topography |precision_max= 93m (3"arch) |covered_area= 60⁰N-56⁰S (landmass only) |datum= WGS  84 |extensions= .tif |size_compressed= |size_uncompressed= |tile_size= on command |tiles_total= 1 |comment = Perfect for small areas anywhere in the world. Need to create a free account. Worth it. You will use this source frequently. |editor_note= For this tutorial, and since GIS data are quite heavy (SRTM3 90m, Aster 30m), select and download the smallest area possible (Taiwan, Hongkong are good choices with both sea and mountains).}}

{{summarizationCollapse|title=: Depreciated 'tiles download' approach|1=

Formerly, high precision topographic GIS datas being too big —about 60GB for the whole Earth—, these datas were split into dozens, hundreds, or thousands small tiles about some MB each. The mapmaker had to find, download, unzip, load the several needed tiles (say 10 tiles for Danemark), and manage these 10 tiles in parallel for color styles, effects, etc. However, the process is a more complex than downloading a single file. You will need to:

# '''Know''' the coordinates of the area you want to map—although you do have the option of visually selecting the area on the download page.

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Since the ETOPO1 data is a raster file, go ahead and add it to your project using whichever ''Add Raster Layer'' method you prefer.

<div class="center">

<gallery widths="500px" heights="300px">

file:QGis_Data_load_-_01_raster_topography.png |1. Adding a raster layer.

file:QGis_Data_load_-_02_raster_topography.png |2. Topographical data will appear in grey.

</gallery>

</centerdiv>

=Links=