On Thursday, 11 August 2011, at 22:34:00 +0200, Marie-Noëlle Augendre wrote:
> But I dont know how to set up the coordinates/projection/mode/etc. in > the "convertir un fichier Tiff au format Geo Tiff par > géoréférencement" screen of QLandkarteGT. Is there some HowTo > somewhere? Or could you provide some explanation? > Let's see if I can explain it in an easy way. First, go to Carte -> Editer/Créer une carte. The dialog for referencing a TIFF file (and only TIFF files, so convert them to that format before proceeding) will open on the right part of QLGT's interface. First, open the .tiff file "Ouvrir un fichier". Then, configure the "Projection de la carte" (that is, the coordinate/projection system coordinates on the TIFF file are defined for). For example, for the usual paper maps in Spain, it is "UTM zone 30 North, Datum European_1950). I understand the "Projection de référence" is the projection/datum on the resulting file. Use whatever fits you best. If you are going to stich several files together, use always the same for every fragment. In Mode you have to select how many point to provide QLGT for it to referenciate the image. For square pixel and coordinates very precise on the map, "pixels carré (2 points)" should be enough. Step 1 should be done. Next on to step 2: provide the (two in the example) points to use to reference the image. Click "ajouter une référence", and an orange marker will show centered on the map viewport, and an entry added to the step 2 list. Move and zoom the map until you see at an adequate zoom level one of the points with known coordinates, and right click on the map. Take note of the "Pixel" coordinates, and edit the list entry to make x and y match the pixel coordinates (double click each field to edit). Then input the map coordinates double clicking on the Coord. field for the point besides the big green number 2. Help icon on the right shows the different coordinate formats you can use (omit the double quotes). Repeat for the second point in the map with known coordinates. When finished, click "Converti!" and wait for the process to end (see the bottom progress messages from "gdal"). A "Fichier de sortie" would have been created as a result, as a georeferenced version of the original file. To check if the process was done right and coordinates on the maps correctly entered, load some GPS data on top of the map, and see if it matches the map. If not, something was not ok along the way. > Additionally, I'd like to know whether I need to assemble all my > screecopies in one huge file in order to have one map; or is it > possible to navigate to one map to the adjacent one without having to > group all of them in one. > The easiest way would be to georeference all your partial maps as shown above, and then create a QMAP out of them, to show all at the same time, at the same zoom levels. A QMAP is a collection of maps to show at different zoom levels: for your case, you would have to create one with, for every zoom level, shows every maps you want to include in the set. So "Carte -> Editer/Créer une carte" again, but this time choose "Créer une carte à partir des fichiers existant géoréférencé". Create a new file name, give it a descriptive comment, and "ajouter" all files at the same zoom levels, for example at zooms 1-256. "Sauvegarder" changes, and that's it (it's easier to understand looking at the interface than explaining). Just make sure all georeferenced files are using the exact same projection/datum , or else the QMAP will not be created. Hope this helps. Greetings, -- Jose Luis Domingo Lopez Linux Registered User #189436 Linux Kubuntu 11.04 (Linux 2.6.38-8-generic-pae)
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