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Friday, 22 June 2012

ARCGIS and polygons (for Landsat imagery)

Objective:  To calculate the area of a polygon extracted from a Landsat scene, using ARCGIS 10. Credits as well as copyrights are the same of the previous entries (Buitrón and Fernandez, 2012).

1. Create a folder DATA GIS where to store the archives to be created in ARCGIS.
2. Open ArcMap 10. Go to Catalog and search the folder DATA GIS. Inside create a new folder and set the name of the image l519971016, Inside this folder create a Personal Geodatabase, using the name of the image; inside it create a FeatureDataset with the name GLACIER Next and will pop up a window “New Feature Dataset”. Go to “GeographicCoordinateSystem” and “Import”; load the image l519971016.shp Add Next, then it will appear the same window, go to “Vertical CoordinateSystems” “World” “WGS 1984” ”Next” “Finish”
 3. Inside the folder GLACIER create several FeatureClass using the name of the glaciers we wish to delineate. 
4. Inside the folder GLACIER go to “Import” FeatureClass (single) and in “Input Features” search for the image in shape format. In “Output Location” save inside the folder GLACIER; in “Output FeatureClass” write down the name GLAS and OK

4. On the table of Contents can be seen all folders that have been created inside GLACIER, but only GLAS has the image l519971016.shp, since the remaining ones are empty.
5.   Go to “Editor”StartEditing and go to SelectFeaturesbyrectangle”, with this tool select the corresponding directory of every glacier.

6.         In the toolbar go to “Edit” Cut, then the selection will disappear; again in “Edit” Paste and select the locations where the image will be pasted. Do the same procedure with all glaciers. To finish, go to “Editor” “Stop Editing”. At the end, the folder GLAS will be empty and the folders of the glaciers will store the data of the corresponding glacier.

7.         If you open the table of attributes of each folder, you will see that every glacier is composed by several polygons. Then, to join all that information into a single polygon, in the toolbar go to “Geoprocesing” Dissolve, in “Input feature” load the archive of, e.g., the glacier SAJ and in “Output FeatureClass” direct the file to the address where the archive will be stored e.g., with the name “SAJAMA” OK.
When opening the table of attributes of SAJAMA, you will see that all the information has been joined. In this table you will find the information on the area, the perimeter, etc, of the glacier.

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