I hope the mara of the Cartesians apologize for publishing such an obvious post, because this is in the Readme of Google Earth, hehe
But well, in response to a request that I see some days ago in the statistics; here the post. As we mentioned before, within the evils of Google Earth is to be a catalog of products of satellite image providers, among others the high resolution images taken by the satellite called SPOT, in passing is the French abbreviation for Satellite Pour l'Observation de la Terre that from the SPOT5 launched in 2002 multispectral images of up to 2.5 meters are obtained.
1. Turn on SPOT coverage
To activate the layer of SPOT satellite images is done in the left panel indicated in the figure, this way you can see the existing shots in orange lines. You have to get away a little to see them, and in the icons of the center of the roofs you get a link to be able to have a preview of the image and even a button to make the purchase of this one.
2. Image Details SPOT
The details of the image include information such as:
Satellite: SPOT 5 (Satellite that made the shot)
Date: 23 DEC, 2007 18: 30: 56 UTC (Date taken, United Time Central, or the United States Time Center)
Product: 2.5 m color (Pixel size and whether the image is in color or grayscale)
Incidence angle: -5.03957 ° (angle of capture with respect to a vector that would go to the center of the earth ... I guess)
ID: 55442840712231830562J (Image Identifier)
Note: Vegetation appears in red on raw color images. (this means that the coloration is equivalent to the interpretation of light by the satellite, not that the forests are on fire :))
Spot Image is the leading supplier of geographic information derived from satellite imagery for professional and private use.
“One World, One Year” portrays the most recent SPOT images acquired over the past 12 months. It is a selection of images ranging from 2.50 meters to 20 meters resolution.
This means that the images shown in the Google Earth catalog are not the only ones that exist, but rather those of greater demand ... and that not all of them have a resolution of 2.50 meters but vary up to 20 meters per pixel.
These coverages they are not useful for high precision work, before a pixel walked the 20 meters, now walk the 2.50 or less (GeoEye promises which will have 0.25) However, the problem is that because it has such a wide coverage, the curvature of the earth has an impact, so the relative accuracy of one point with respect to another near (about 100 meters, for example) is quite good ... but with respect to a distant one (about 2000 for example) ... there are no guarantees ... and that is what is solved with orthorectification and the difference is perceived when comparing an ortorectified image of a flight to 5,000 meters high, with enough points control ... to an image of a satellite taken at 822 kilometers high.
However, these images are very useful for forestry projects, risk mitigation, environmental, historical, etc. The advantage they have is that they are satellite captures, that is, results of the interpretation of a satellite based on the reflectivity of light and other herbs this complex ... they are not aerial photographs, but many programs have applications that allow special analysis on this type of image that can be acquired with terrain elevation data (DEM).
3. SPOT image coordinates
To know the central coordinate of these images, select the option “get the image“, then a panel appears where there is more information such as the latitude and longitude of the center of the image, percentage of cloud cover, price and a button to obtain a formal quote.
The example that I have shown you is worth €8,100, but in case you want to see other coverages you can go to “view more acquisition online” and you will surely find lower priced images although not as recent. The "recent" criterion is worth mentioning, it lowers costs and in some cases an image from a couple of years ago can be equally useful depending on the purposes or ignorance :).
4. Images of specific areas
Once you enter the selection panel you can choose either:
- Location Coordinates
- Choose by region, country, department, municipality
- Choose pixel size, from 2.5 to 20 meters, either capture or resolution, or 3D with digital model elevation data (DEM)
- Date of the image
- Chance of Rain
- Maximum incidence angle
Once the parameters are chosen, the system shows you the available options and prices.