Let's talk about GIS
Greetings to all!
It was with this topic that I got into the ranks of Habrahabr users, for which I would like to sincerely thank comrade fatum . Well, now the article itself, carefully pulled out of the drafts.
Today we will talk about geo-information systems, which every day more and more invade our daily life. This article will discuss general issues concerning the principles of remote sensing, one interesting resource that provides satellite images completely free of charge, as well as the question of who and why all this is necessary, what can be done using images and specialized programs ... All this, Of course, it will be touched only superficially, since more than one article will be required for detailed coverage of the issue ... So let's begin
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What are the advantages of remote sensing (that is, observation and surface images of any body from a distance - whether it be taking pictures from a space satellite or an airplane, or getting bottom relief from a vessel using an echo sounder) over traditional mapping methods? The most important advantages are the absolute accuracy of the transmission of the spatial structure of objects and, of course, the ability to regularly update data, which allows analyzing multi-temporal data and identifying the dynamics of modern landscapes, watching changes in simple words, be it forest boundary retreat, associated in most cases with logging, or drying up of rivers, desertification and other important processes.
From the school course in physics, we all know that electromagnetic waves can be divided into spectra depending on their length. Different spectra of shooting have a different thematic focus:
On this, I think, it is worthwhile to finish a little boring theory about images and tell about the Internet sources of primary remote sensing data (often, the abbreviation for remote sensing data is used).
I will talk about a rather useful and, most importantly, free resource - http://zulu.ssc.nasa.gov/mrsid/mrsid.pl
Here you can get pictures for 1990 and for 2000 from Landsat 4/5 and Landsat 7 satellites respectively. The principle of operation is as follows:
We click on the map on the desired territory until we see the required area-square
Put a tick Select Image and click on the desired square (in my case, the square N-37-40_2000)
After reloading the page we get a pop-up window with the selected site. Clicking on the sides of this image you can move north / south / west / east of the current position. You can change the size of the image in the right drop-down list and the degree of approximation in the left drop-down list.
When choosing the scale and size of the image, click on the desired area and get the desired image
Just below the image itself is a link to the archive with this image in the MrSID format. After extraction, this image can be opened in various specialized programs - ArcViewGIS, MapInfo, GlobalMapper and other
The results of image processing are different cards. An excellent example is the land use maps of a particular region, taken entirely on a satellite-based image. The process of creating a landscape map is more laborious, as it combines not only the work with “hands”, but also the work with “head”. Here is an example of a map made on topographic map-based and images.
On the Internet you can also find quite interesting animation maps obtained using remote sensing data. Here is one such example from www.spot-vegetation.com
This shows the dynamics of vegetation cover throughout the year. It is both visual and informative.
It was with this topic that I got into the ranks of Habrahabr users, for which I would like to sincerely thank comrade fatum . Well, now the article itself, carefully pulled out of the drafts.
Today we will talk about geo-information systems, which every day more and more invade our daily life. This article will discuss general issues concerning the principles of remote sensing, one interesting resource that provides satellite images completely free of charge, as well as the question of who and why all this is necessary, what can be done using images and specialized programs ... All this, Of course, it will be touched only superficially, since more than one article will be required for detailed coverage of the issue ... So let's begin
')
What are the advantages of remote sensing (that is, observation and surface images of any body from a distance - whether it be taking pictures from a space satellite or an airplane, or getting bottom relief from a vessel using an echo sounder) over traditional mapping methods? The most important advantages are the absolute accuracy of the transmission of the spatial structure of objects and, of course, the ability to regularly update data, which allows analyzing multi-temporal data and identifying the dynamics of modern landscapes, watching changes in simple words, be it forest boundary retreat, associated in most cases with logging, or drying up of rivers, desertification and other important processes.
From the school course in physics, we all know that electromagnetic waves can be divided into spectra depending on their length. Different spectra of shooting have a different thematic focus:
- The blue zone . The images obtained in this zone best reflect the coastal lines of water bodies, they can be distinguished by various types of soil and man-made objects.
- Green area . Vegetation stands out and again water bodies.
- Red zone . The difference of vegetation by type (it is possible to distinguish different types of forests by shade), soil types and man-made objects.
- Middle infrared area . Analysis of snow and ice cover
- Thermal infrared area . Allows you to register fires
On this, I think, it is worthwhile to finish a little boring theory about images and tell about the Internet sources of primary remote sensing data (often, the abbreviation for remote sensing data is used).
I will talk about a rather useful and, most importantly, free resource - http://zulu.ssc.nasa.gov/mrsid/mrsid.pl
Here you can get pictures for 1990 and for 2000 from Landsat 4/5 and Landsat 7 satellites respectively. The principle of operation is as follows:
We click on the map on the desired territory until we see the required area-square
Put a tick Select Image and click on the desired square (in my case, the square N-37-40_2000)
After reloading the page we get a pop-up window with the selected site. Clicking on the sides of this image you can move north / south / west / east of the current position. You can change the size of the image in the right drop-down list and the degree of approximation in the left drop-down list.
When choosing the scale and size of the image, click on the desired area and get the desired image
Just below the image itself is a link to the archive with this image in the MrSID format. After extraction, this image can be opened in various specialized programs - ArcViewGIS, MapInfo, GlobalMapper and other
The results of image processing are different cards. An excellent example is the land use maps of a particular region, taken entirely on a satellite-based image. The process of creating a landscape map is more laborious, as it combines not only the work with “hands”, but also the work with “head”. Here is an example of a map made on topographic map-based and images.
On the Internet you can also find quite interesting animation maps obtained using remote sensing data. Here is one such example from www.spot-vegetation.com
This shows the dynamics of vegetation cover throughout the year. It is both visual and informative.
Source: https://habr.com/ru/post/67144/
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