QGIS/C2/Coordinate-Reference-Systems/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to this tutorial on Coordinate Reference System in QGIS. |
| 00:07 | In this tutorial, we will learn to, |
| 00:10 | Add layers to projections in QGIS. |
| 00:15 | View metadata information for layers. |
| 00:19 | Save selected features from a layer to a new layer. |
| 00:24 | Re-project and overlay data layers of different projections together. |
| 00:30 | To record this tutorial I am using,
Ubuntu Linux OS version 16.04, QGIS version 2.18 |
| 00:42 | To follow this tutorial you should have basic knowledge about GIS. |
| 00:49 | Please view previous tutorial in this series. |
| 00:54 | About Coordinate Reference Systems, |
| 00:57 | Coordinate Reference Systems are of two types,
Geographic coordinate system, and Projected Coordinate System |
| 01:06 | Most widely used geographic coordinate system is WGS 84. |
| 01:12 | Most widely used projected coordinate system is UTM. |
| 01:18 | Here I have opened QGIS interface. |
| 01:23 | On the canvas, world map with country administration boundaries is displayed. |
| 01:30 | Demonstration on how to download the map and display in QGIS is explained in the prerequisite tutorial. |
| 01:39 | Please view the pre-requisite tutorial. |
| 01:43 | This file can also be downloaded from the Code files link. |
| 01:48 | On the left-side of the canvas, you will see Layers Panel, with file name of the world map as a layer. |
| 01:57 | By default Layers Panel is enabled here. |
| 02:02 | If not, we can enable or disable the Layers Panel using View menu. |
| 02:08 | Click on View menu on the menu bar.
Scroll down and select Panels option. |
| 02:16 | Sub-menu shows a list of panel names. |
| 02:21 | Click on Layer Panel option to enable or disable the panel. |
| 02:27 | We can adjust the size of the panel by dragging the boundary. |
| 02:32 | If you wish to change the color of the map, right-click on the layer name in the Layers Panel. |
| 02:39 | Scroll-down the context menu and select Styles option. |
| 02:44 | Sub-menu shows a color triangle . |
| 02:48 | Choose the color by rotating the vertex of the color triangle. |
| 02:53 | Click anywhere on the canvas to close the context menu. |
| 02:58 | At the bottom-left corner, on the status bar of QGIS window, you will notice the label Coordinate and a text box with numbers. |
| 03:09 | Values of X and Y coordinates for a particular location are shown in this text box. |
| 03:17 | Move the cursor over the map. |
| 03:20 | Observe, that the values of X and Y coordinates change with location of the cursor. |
| 03:28 | By default Render option is checked on the status bar.
Leave it as such. |
| 03:37 | On the status bar, at the bottom-right corner, you will see another label, Current CRS |
| 03:44 | This code represents the current Projection Coordinate Reference System. |
| 03:50 | To determine a layer’s projection, we can look into the metadata. |
| 03:56 | On the Layers Panel, right-click on the layer name. |
| 04:01 | From the context menu, select Properties.
Layer Properties dialog-box opens. |
| 04:09 | In the dialog-box, on the left-side panel, click on Metadata option. |
| 04:15 | Under Properties section, scroll down the slider. |
| 04:20 | At the bottom, under heading, Layer Spatial Reference System, you will see the definition for this projection. |
| 04:29 | It shows WGS84 as geographic coordinate system. |
| 04:35 | Click on Ok button at the bottom, to close the dialog box. |
| 04:41 | Let us now add layers to the map and change the projection. |
| 04:47 | About data layers. |
| 04:50 | Usually geographical data is stored in layers in a GIS workspace. |
| 04:57 | Each layer has data stored in its attribute table. |
| 05:02 | Many layers can represent data of the same geographical location. |
| 05:08 | Back to the QGIS interface. |
| 05:12 | Now let us see how we can change the layer’s projection. |
| 05:17 | This operation is called Re-Projection. |
| 05:21 | Instead of re-projecting the entire layer, we will re-project some features. |
| 05:27 | On top-right corner of the tool bar, click on Select features by area or single click tool. |
| 05:35 | Click on the black triangle next to this tool. |
| 05:39 | From the drop down choose Select features. |
| 05:44 | On the world map displayed on canvas, click on the United States of America feature to select it. |
| 05:52 | Note that, the United States of America is shown in a different color. |
| 05:58 | We will now change the projected coordinate system of this layer and save. |
| 06:04 | Right-click on the layer name in the Layers Panel. |
| 06:08 | Scroll down, select Save As option. |
| 06:12 | Save Vector Layer as... dialog box opens. |
| 06:17 | The default format option is ESRI Shapefile.
Leave it as such. |
| 06:26 | Click on Browse button next to File name text box. |
| 06:31 | Save layer as... dialog-box opens.
Name the output layer as USA-1.shp. |
| 06:41 | Find a suitable location to save.
I will save it on Desktop |
| 06:48 | Click on Save button at the bottom. |
| 06:52 | In the Save Vector Layer as.... dialog-box, the file path appears in the File name text box. |
| 06:59 | We will choose the new projection for this layer. |
| 07:03 | Next to the CRS drop down box, click on Select CRS button. |
| 07:10 | In the Coordinate Reference System Selector, in the Filter search box, enter North America |
| 07:17 | Under Coordinate reference systems of the world, under heading Projected Coordinate System, scroll through the results. |
| 07:27 | Select, North_America_Albers_Equal_Area_Conic (EPSG:102008) projection. |
| 07:37 | Click on OK button at the bottom. |
| 07:41 | In the CRS drop down box, the newly selected CRS is shown. |
| 07:47 | Click on the check box to check Save only selected features option. |
| 07:53 | This will ensure that only the selected feature gets re-projected and exported. |
| 08:00 | Here, by default, Add saved file to map option is checked. |
| 08:06 | If not, click on the check box to check this option. |
| 08:11 | Click on OK button. |
| 08:14 | The re-projected layer gets loaded, in a different color. |
| 08:19 | These two layers are now in different projections. |
| 08:24 | Observe that, on Layers Panel, you can now see 2 entries. |
| 08:30 | Notice that the new United States layer overlays perfectly on top of the world map layer. |
| 08:38 | This is because QGIS has a feature called On-the-fly CRS transformation. |
| 08:45 | The projection text at the bottom-right corner of QGIS window has the words, OTF next to EPSG:4326. |
| 08:56 | Select the United-States layer in the Layers Panel by clicking on it. |
| 09:02 | Click on the Current CRS text, EPSG:4326, at the bottom-right corner of the status bar. |
| 09:11 | Project Properties CRS dialog-box opens. |
| 09:16 | Let us turn-off the Enable on-the-fly CRS transformation and see what happens. |
| 09:23 | Uncheck the Enable on the fly CRS transformation check box, by clicking on it.
Click on OK button at the bottom. |
| 09:34 | Back in the main QGIS window, you will see the world map disappear. |
| 09:40 | You can see only the United States map on the canvas. |
| 09:45 | This is because the Projected CRS for this layer changed to Albers Projection. |
| 09:52 | The coordinates and scale are different now. |
| 09:56 | Right-click the United States layer in the Layers Panel. |
| 10:01 | Select Zoom to Layer option. |
| 10:05 | Now you will see the United States in the selected projection. |
| 10:10 | Again, click on the Current CRS text to open Project Properties dialog-box. |
| 10:17 | Turn-on the Enable ‘on the fly’ CRS transformation option. |
| 10:23 | Under the heading Recently used Coordinate Reference Systems, select WGS 84.
At the bottom, click on OK button. |
| 10:35 | The display on the canvas will return to its previous state with world map. |
| 10:41 | To delete the vector layer from the dataset, right-click on the name in the Layers panel. |
| 10:48 | From the context menu, click on Remove option. |
| 10:52 | A prompt appears to confirm the action.
Click on OK button. |
| 10:59 | Observe that the layer is removed from the dataset. |
| 11:04 | Let us summarize, |
| 11:07 | In this tutorial we have learnt to
Add layers to projections in QGIS. |
| 11:15 | View metadata information for layers. |
| 11:19 | Save selected features from a layer to a new layer. |
| 11:24 | Re-project and overlay data layers of different projections together. |
| 11:30 | As an Assignment:
Project The United States with North_America_Lambert_Conformal_Conic projection and observe the difference. |
| 11:43 | Re-project the entire world map layer into World Mercator projection system. |
| 11:50 | Your completed assignment should look like this. |
| 11:55 | The video at the following link summarizes the Spoken Tutorial project. Please download and watch it. |
| 12:03 | The Spoken Tutorial Project team: conducts workshops and
Gives certificates on passing online tests. For more details, please write to us. |
| 12:15 | Please post your timed queries on this forum. |
| 12:19 | Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.
More information on this mission is available at this link. |
| 12:31 | This tutorial is contributed by Prajwal. M from Sahyadri college of Engineering and Snehalatha from IIT Bombay.
Thank you for joining |
