Landsat satellite introduction
The Landsat satellite (LANDSAT) series of satellites is jointly managed by NASA and the US Geological Survey (USGS). Since 1972, 8 LANDSAT series satellites have been launched one after another (the sixth one failed). Landsat1-5 have been decommissioned at present, and landsat7 has since June 2003, the data gap data caused by the failure of the scan line corrector (SLC) of the sensor, but it is still running. Landsat8 was launched on February 11, 2013, and began to acquire images after 100 days of test operation, and is still in operation, as shown in Figure 1.
Figure 1 Brief introduction of 8 Landsat satellites
Landsat satellite data introduction
Landsat1-5 are equipped with MSS sensors (as shown in Figure 2), landsat4 and 5 are equipped with a TM sensor (as shown in Figure 3), Landsat7 is equipped with an ETM+ sensor (as shown in Figure 4), and Landsat8 is equipped with an OLI And the TIRS sensor (Figure 5, Figure 6). parameters of each sensor.
Figure 2 MSS sensor
Figure 3 TM sensor
Figure 4 ETM+ sensor
Figure 5 OLI sensor
Figure 6 TIRS sensor
Landsat satellite data download
1. Enter the earthexplorer website
The data can be downloaded at https://earthexplorer.usgs.gov/. Before downloading data, you must register an account (if you already have an account, log in directly), otherwise you cannot add the order after the data is retrieved, which may lead to retrieval in vain. The homepage of the website is shown in Figure 7, and the upper right corner is the login button. If you have already logged in, your user name will be displayed.
Figure 7 The homepage of the earthexplorer website
2. Search criteria page
On the search criteria page, there are two search methods: Geocoder and KML/Shapefile Upload, as shown in A in Figure 8.
Geocoder, as the name suggests, uses various geographic codes, and there are three "Geocoding Method": Feature (GNIS), Address/place, path/row , as shown in B in Figure 8.
Figure 8 Search criteria page
2.1 Feature (GNIS) search method
Feature (GNIS) selects the range according to the country-province. For example, we can select each state in the United States under "US Features" to retrieve data (as shown in Figure 9), and the result is the data within the state; and in Under "World Features", you can retrieve the data of countries other than the United States. If you want to retrieve the data of Beijing, as shown in Figure 9, select CHINA—Administrative boundary Features—First-order administrative division, and then click "show" It can retrieve the scope of China's first-level administrative divisions, and click "Beijing Shi" to determine the latitude and longitude position.
Figure 9 Use Feature (GNIS) to select Beijing; then click Beijing Shi to display the latitude and longitude position
2.2 Address/place search method
Address/place is to directly enter the address, as shown in Figure 10, enter Beijing (both Chinese and English are acceptable), and then click "show" to retrieve the range of Beijing, and click "Beijing, China" to determine the latitude and longitude location.
Figure 10 Use Address/place to input Beijing; then click "Beijing, China" to display the latitude and longitude position
2.3 path/row retrieval method
The path/row is retrieved based on the strip number of the landsat satellite data, for example, you already know that the data is P137R035. If you select Point in Figure 11A (the default option), and Type in Figure 11B selects WRS2 (the retrieved range is somewhat wrong when I select WRS1), then when you enter path as 137 and row as 035, click show The center point position of the data will be retrieved. And if you select Polygon in Figure 11A, when you input path as 137 and row as 035, click show to retrieve the coverage of the data.
Figure 11 Use path/row to retrieve data; point shows the position of the center point; polygon shows the coverage of the data
2.4 Select time
After determining the space range, enter the time selection page, as shown in Figure 12. Under Date Range, you can specify the time range of the data, or you can retrieve it by month (Search months, the default is all months). After the time is determined, you can also filter the amount of cloud coverage (the default is to retrieve the data from 0 to 100% cloud coverage, which is generally ignored). In addition, you can also choose the way to display the results. The default is to display 100 items on one page (this is ignored during the actual download process).
Figure 12 Select time, cloud cover, and result display mode
3. Data set selection page
Switch to the Data sets page (if you do not specify a data set on this page, you will get the data of all satellites in the selected time period), as shown in Figure 13. Select the dataset under Landsat, here I need the data of Landsat7 ETM+.
Figure 13 Select Dataset
4. Additional Criteria selection page
This page is filtered by some other special conditions, which can be set according to your own needs.
Figure 14 Other filter conditions
5. Results page
Next, switch to the Results page and view the results, as shown in Figure 15. When the amount of data is large, a page such as "Searching for Data" will appear, do not click "Cancel", just wait for a while. After the search is completed, there will be data that meets the conditions. Here I need the second piece of data, so I need to click the button in the red box. If the addition and download are successful, the "Item Basket" in the upper right corner will change from 0 to 1, indicating that a piece of data has been added. Notice! ! ! Be sure to log in first, otherwise it cannot be loaded into the download list.
Figure 15 result display
6. Data download page
Click "Item Basket" in the upper right corner, and you will enter the interface in Figure 16. Confirm the number of images. This time I added a piece of data, and now it shows "1 Scenes", which is correct. Click "Start Order".
Figure 16 Data download interface
Check whether the order data is correct, and then click "submit product selections" to submit the order, as shown in Figure 17. After that, you will receive the email of the submitted order, as shown in Figure 18, and then you will receive the email of the completion of the order processing in about 20 minutes, as shown in Figure 19. At this time, you can click the Order Status URL in the email to download the data.
Figure 17 Order submission
Figure 18 Order Submission Email
Figure 19 Order completion email