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Map Service |
A problem of units ? of terminology ? Consult the Education service. |
Map content
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Since 2009, a on-request service delivery of irradiation maps creation is available. This service is on request only, thus please contact our support-sales for a quotation. The illustration on the right depicts the coverage of the HelioClim databases, and thus the available countries for the map creation. Here are the options: |
 
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Visualisation of GeoTiff 16 bits maps
For you to visualise the maps we created, you need a tool able to handle georeferenced tif images coded on 16 bits. We personnaly use the free software QGIS version 1.6.0 named Copiapó. You can download this soft here. This paragraph aims at helping you with the first steps of Qgis. First use the button that you see on the first Qgis screenshot 1 to add a raster layer in your Qgis environment. |
 QGIS SCREENSHOT 1 |
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| The result of this operation is to add a new raster layer in the box named "Layers" ("Couches" in French), as you can see on the second Qgis screenshot2. The problem is now that your image appeared in black. You need to specify a correct color table to your image for a correct visualisation. You need to right click on the layers and select the menu "Properties". |  QGIS SCREENSHOT 2 |
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| In the left menu "Convention of signs", Select "Color Palette" in the section "Color Palette", as shown in the screenshot 3. |  QGIS SCREENSHOT 3 |
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| You also assign a transparent color to a value in your image. In our case, the values outside the countries are set to 0, thus you need to specify that the 0 value is 100% transparent, as it is written in the Qgis screenshot 4. |  QGIS SCREENSHOT 4 |
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| Finally, click on the left menu "Color Palette". Then click on the open file icon (inside the red circle) to enter a default color palette, or add a new one by hand. An example of color palette (the one on the display) can be downloaded here. |  |
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| Here is the final result you can obtain the GHI map over Greece, with the selected palette of colors. |  QGIS SCREENSHOT 5 |
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FAQ on maps
| Q.1 When I compare the irradiation value at a given pixel location on the map, with the value retrieved through the website, the values are slightly different. What is the origin of this difference ? | ||
| The map are built with the raw HC3 pixel value from the database. The altitude used for the whole pixel is the average or central altitude of the pixel. On the contrary, with a website request, the irradiation is corrected with the SRTM-v8 (90 m of spatial resolution) database altitude. As a consequence, hilly of mountainous areas, the differences between these values might be very inportant. |
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| Q.2 According Google Earth, my site is 1 km inland, whereas on the map the corresponding location is on water. Why? | ||
| The reason is due to the spatial resolution of the map. The figure on the right corresponds to a map of yearly irradiation average over 6 years, in normal incidence. The black line is the coast, where the water is at the bottom of the image and in-shore is at the top. The colors in the squares are the DNI HelioClim values of the map: orange for irradiation values between 2300 and 2400 kWh/m² and red for values between 2400 and 2500 kWh/m². As a consequence and according to this map, if you select a geographical location inland, but where most of the pixel is off-shore, it will be considered as off-shore on the map. |
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Last update: 10/26/11 5:47 PM