Geographic Information Systems GIS for BSIT

Geographic Information Systems

1. QGIS (GEOGRAPHIC INFORMATION SYSTEM)

2. Importing Spreadsheets or CSV files Many times the GIS data comes in a table or in a spreadsheet. QGIS allows you to import structured text files with coordinates as a vector layer. This lesson shows how you can use the  Data Source Manager  to import  Delimited Text  files.

3. Overview of the task We will be importing a text file with earthquake locations in the tab-separated values (TSV) format to QGIS and create a points layer.

4. Get the data 1. For this tutorial we will download a dataset of earthquakes between 1900-2000 from NOAA’s National Geophysical Data Center produces a great dataset of all significant earthquakes since 2150 BC.  Visit the NOAA NCEI portal  and enter Min as  1900  and Max as  2000 . This will return all earthquake incidents that occurred and were recorded by NOAA between those years. For other specific results, you can filter with different parameters. Click Search.

5. As a result, we got  2594  earthquake incidents. Click on the  Download TSV  icon.

6. For convenience, you may directly download a copy of the above datasets from the link below: earthquakes-2023-09-12_17-19-15_+0530.tsv Data Source  [NCEI]

7. PROCEDURE

8. Examine your tabular data source. The downloaded earthquake database contains the  Latitude  and  Longitude  fields indicating the location of the earthquake epicenter and other related attributes. We will use these fields to import the file as a point layer. Open the data in a text editor such as Notepad/ TextMate to view the contents. You will see that a TAB separates each field.

9. Note If you have a spreadsheet, use  Save As  function in your program to save it as a  Tab Delimited File  or a  Comma Separated Values (CSV)  file.

10. 2. QGIS comes with a unified data manager that allows you to load all the various supported data formats. Click the Open Data Source Manager button on the Data Source Toolbar. You may also use Ctrl + L keyboard shortcut.

11. In the  Data Source Manager  dialog box, switch to the  Delimited Text  tab. Click the  …  button next to the  File name .

12. Depending upon the operating system, you may or may not view the file at the downloaded location. In File formats, switch to  All files (*; *.*)  to view the  tsv  file.

13. Now you will see the downloaded file. Select that and click  Open .

14. In the Data Source Manager dialog box, the path to file will be available in File Name. Change the Layer name to  1900_2000_earthquakes . In the File format section, select Custom delimiters and check  Tab . In the Geometry definition section, choose Point coordinates. By default X field and Y field values will be auto-populated if it finds a suitable name field in the input. In our case, they are  Longitude  and  Latitude . You may change it if the import selects the wrong fields. You can leave the Geometry CRS to the default  EPSG:4326 - WGS 84  CRS. If your file contains coordinates in a different CRS, you could select the appropriate CRS here. Click Add.

15. Note It is easy to get confused between X and Y coordinates. Latitude specifies the north-south position of a point and hence it is a  Y  coordinate. Similarly Longitude specifies the east-west position of a point and it is a  X  coordinate.

16. You will now see that the data will be imported and displayed in the QGIS canvas as a new layer called  1900_2000_earthquakes  with CRS  EPSG:4326 .

17. THANK YOU!