Qualche giorno fa abbiamo parlato dell'attivazione, da parte di GeoWeb, del servizio Geo-Sit, che permette la sovrapposizione degli estratti di mappa prelevati da Sister sulle ortofoto del territorio. Il servizio è certamente interessante e di facile utilizzazione, ma il prodotto finale ha una scarsa definizione e soprattutto costa 2,16 Euro (1,80+iva).
Ma se non ci spaventa scaricare qualche programma e lavorare un po di copia ed incolla, potremo ottenere lo stesso risultato (in alcuni casi anche meglio) e, cosa che di questi tempi non guasta, gratis.
Innanzi tutto need to download two programs which are obviously free to use: one is P DF-Xchange Viewer a useful pdf file viewer that contains interesting features (ability to perform measurements in both linear scale of areas, ability to write and draw on pdf documents, etc..), the other is PhotoFiltre, a graphics program (Photoshop Style) that has nothing to envy to the most noble and software for which they were developed interesting plug-in (one on one for many linear and angular measurements on the drawings). These are the link for the drain:
PDF-Exchange
L'ultimo link è un tutorial di PhotoFiltre utile per un primo approccio al programma.
Una volta scaricati ed installati i programmi (entrambi sono "portable" e quindi can be placed wherever you want and also work from a USB drive), first we must transform our extract map to PDF, JPEG image. To do this we open the file extract with Pdf-Xchange, then click the right button in the viewing window (context menu) and select Export -> Export as Image. At this point we will see the window below.
We then select the destination folder and file name. Set the resolution to 300 (a good compromise between the definition and size of the file) and click on Export.
Without this, we will secure a good orthophotos of the area of \u200b\u200binterest. There are several sites that offer the opportunity to have aerial photographs of the area (GoogleMaps, GoogleEarth, Bing, etc.). But I find that the more established (at least in my zone) is the site of the Yellow Pages ( http://www.visual.paginegialle.it ). So let the area that interests us (by selecting the photo and map) and zoom to the maximum, center (if we want we can also put the full screen display) and press the button at the same time Shift (upper) and the Print Screen key (the top near the function keys). In this way we captured the screen as an image.
PhotoFiltre Open and then select the menu go to Edit -> Paste as new image and save as.
loads even the map you saved earlier.
Now cut out the area we are interested overlap. Board of aerial crop the photo a bit larger than the area we're going to cut to the map, so you have a bit of margin on all sides for a better calibration.
To crop, just press the left mouse button and draw a rectangle that contains what you want. If the transaction is made by holding down the Shift key is drawn a square.
done, click on the right mouse button and select cutter and so we cut our image in the desired size. Save both images obtained.
Obviously the two images are not the same scale. In particular, the orthophotos be smaller than the map.
then proceed to enlarge the image of the orthophotos.
To do this we need to select the image (by clicking on the left button mouse button and select the menu Image -> Image Size .
Under New Dimension selected menu item% (percent) instead of cm. and put the value to 400 if we have a map to 1000 or 200 for a map to 2000. We click OK and we will have our larger picture.
We will now select the image of the map and proceed with the Setup menu -> duotone and set the threshold to 200. Click OK and save. This is to give more definition to our image that is originally in shades of gray.
ORTHOPHOTO
MAPPA
Ora dovremo sovrapporre la mappa all'ortofoto.
Selezioniamo il file della mappa e procediamo con il menù Modifica --> Copia .
Selezioniamo l'immagine dell'ortofoto e procediamo con il menù Modifica --> Incolla speciale --> Maschera . A questo punto dovremmo avere la nostra mappa con i dettagli in bianco sovrapposta all'ortofoto.
Senza fare altro, procediamo quindi a scalare l'immagine the map. Notice that the edge of the image is superimposed
dashed. This means that it can be moved and resized. To move just click the left mouse button and drag to resize, simply attach an edge or a corner and, again clicking the left mouse button, move the mouse in any direction. Again if clicking and dragging a corner of the image also holding down the shift will equal a reduction in both directions.
We will then work by trial and error, is moving to resize the image until you find the overlay that best satisfies us. Gli spostamenti possono essere fatti anche con i tasti freccia usati soli o in combinazione con il tasto Shift per uno spostamento più veloce. Una volta fatto, confermiamo con il tasto invio e salviamo il lavoro prodotto.
A titolo esemplificativo riporto il risultato ottenuto per la medesima area sia con Geo-Sit di GeoWeb, sia con il metodo appena descritto. A parte la precisione della sovrapposizione (quella con Geo-Sit GeoWeb non l'ho calibrata) noterete i dettagli che sono nettamente migliori con questa soluzione.
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