Using the Clipper (Raster tools) in QGIS 2.8.1

CLICK HERE TO WATCH YOUTUBE VIDEO DEMO

Task
To demonstrate how to use the Clipper tool in QGIS 2.8.1 to clip out a section of a GeoTIFF image.

Procedure

Add the already registered raster image. Go To Raster > Extraction > Clipper


In the Clipper dialog box, name the output file. For the demo, Extent Clipping mode is selected. Select the extent by dragging the cross cursor to form a square around the area that is to be clipped out. Once that is done, the extent coordinates will automatically appear in the dialog window. Click OK.


A Processing completed message box will appear. A new raster layer will appear on the Layers window.


Right Click on the new layer > Zoom to Layer. The layer will appear in view.


The new layer may not have copied the correct CRS from the layer it was clipped from. To adjust the CRS, Right Click on the new layer >Set Layer CRS


In the dialog box, select the corresponding CRS. For the demo, Minna/Nigeria West Belt is selected.


Zoom to layer and observe the layer is now displaying the appropriate coordinates.


Thank you for the audience.

Creating relationship class in ArcMap 10.2

The post will demonstrate how to create relationship classes using ArcCatalog in Arcmap 10.2

Thing to note
- Relationship classes can only be created within Geodatabases just like subtypes and attribute domains.

Procedure

Let us have a close look at the data available for the demonstration.

On the Table of Contents in green box, there are the layers- Schoollocations and OyoLGA. Schoollocations are point features that are representing schools within the extent of the map. OyoLGA is a polygon feature representing the boundaries of the local administrative units in the same geographical extent.

The purpose of the demonstration is to create a relationship class that will summarize the data on schools according to the local government area in which they are located. By calling up this relationship class in ArcMap, the attribute data on schools within a local government area can be easily listed on a Table.



First a Spatial Join between the Schoollocations (Point features) and OyoLGA (Polygon features) was done using ArcToolBox. The Attribute Table of the layer created from the Spatial Join is exported to the geodatabase as a Table called  TableLGA. See the red box in the Catalog window. Our Geodatabase for the demo is named- relationshipclass.mdb.



An important start is to have a look at the attribute tables of the layers that are to be related to identify a common field they share. For the demo, OyoLGA layer has the ID_2 field showing the ID of each local government area.



The TableLGA table also has the field ID_2.



To create the relationship class, Right Click on the Geodatabase >  New > Relationship Class


In the New Relationship Class dialog window, Fill in a name for the relationship class. The demo relationship is between the polygon layer representing local governing areas and the Point layer= schools.
OyoLGA is the origin table and tableLGA is the destination table. Click Next. – select the relationship type that would be shared (L-R) 2nd screenshot. For the demo- Simple (peer to peer) relationship is selected.

   

Next page, for demo- Both is selected             Next page, One to Many relationship as one local government area can contain many schools.
     

Choosing Yes will allow the relationship class to update anytime more data is added to the attribute table.
In the screenshot to the right, we will select the fields that would form the Join between the two attribute tables. For the demo as shown earlier- ID_2
   

The relationship class (underlined in red in the Catalog pane)– SchoolsLGA is now created in the geodatabase.

To use the relationship class between the Local government area and the TableLGA, click on a point feature on the map. Once a Point feature is selected, the local government area should also become highlighted.  This indicates that a relationship exists.

To view the schools and their attributes - Right Click on the feature layer > Open Attribute Table


Click on the icon (red boxed). the relationship class will show up. Click on the relationship class and the table should show the results.


When User clicks on the local government area feature, the relationship class Table shows the schools in that local government area.


Also on the TableLGA, when user will open the attribute table and use the relationship class icon as done earlier for the OyoLGA layer. Go to the map and click on a Point feature, the list of features in that local government area is displayed on the attribute table of the selected layer.


Relationship class gives the user the ability to summarize data on an attribute table.
Thank you for reading the blog.

Using the Hyperlink tool in ArcMap

This post will demonstrate how to add an hyperlink to a feature in a layer. The feature can be hyperlinked to a document, picture or webpage. For the demo, a jpeg image from the local source is used.

Procedure
In ArcMap, the demo has a layer of polygons representing different parcels. The objective is to add an image hyperlink to each of the individual parcels (polygons) on the layer.



Right Click on the Layer & Open Attribute Table.


Add an empty field that would contain the hyperlink text. Fill the row with the hyperlink address to the picture, document or webpage. For the demo, see the url location in red box in the field- Pix. Save the edits on the attribute table.


Right Click on the layer & Properties.


In the Layer Properties window, click on Display and check the Support Hyperlinks using field. For the demo, Pix field is selected from the dropdown list. Click Apply and OK.


Click on the Hyperlink tool and features with hyperlinks will automatically be highlighted or selected on the map (blue highlight).


Move the Hyperlink tool to the highlighted feature and click to open the hyperlink.


Or Click on the Identifier tool. Select the feature and go to the hyperlink Field. Click on the Url to open the hyperlink.


The jpeg image will open.


Thank you for your audience.

Creating and Publishing web maps with Esri Maps for Office Add-in

Esri Maps for Office is a free Microsoft Excel and PowerPoint Add-in. Esri Maps for Office allows the GI User to visualize excel data as maps right there in the Microsoft Excel workspace. Esri Maps for Office can be downloaded from the ESRI Global site and accessed with an  Esri Global Account.
This post will demonstrate how to use Esri Maps for Office add-in for Microsoft Excel to visualize table data as a map as well as publishing it online.

Things to note
-Download the Add-in and Install on PC or Desktop.
- User must be running an Office version from Microsoft Office 2010.
- The Add-in will install in Microsoft Excel and PowerPoint.
- Inspect the Microsoft Excel and PowerPoint to confirm the Add-in was successful.
- Esri Maps for Office is activated when the user is online.

Procedure
Launch Microsoft Excel. Open the sheet. Excel data must contain address fields such as LongitudeLatitude or Place names.
For the Demo, a excel sheet containing the geographic coordinates of buildings inspected during a survey of their repair state and their attribute data.



Click the ESRI MAPS add-in (red boxed) & Sign In


Sign in when this window opens


Once signed in, Click on Add Map.


When using Cell range option, make sure the cells you need are highlighted before clicking Add MAp so it will automatically be picked up as seen in the previous screenshot.



In the Add Map window, three options are available. For the demo, Cell range is selected.


In the next page, choose Location Type as Coordinates if the address field type on the spreadsheet is XY, or take option that is most suitable to the address field type of the Data on the spreadsheet. For the demo, the spreadsheet address field is in LatLong, so Coordinates is selected from the drop down list.


Next, click on Confirm location columns. Match the coordinates to the values in the proper columns. Choose an appropriate spatial reference. For the demo, WGS 1984 is selected.



Next, Style by Column indicates which attribute field will define how the data will appear on the map. For the demo, Repair State is selected as the survey was to illustrate which buildings are in good or bad repair state.


The Select Style window automatically uses different colour symbols to group similar values in the attribute field. Click Add data.

A Confirm options window opens up. Click Add data after confirming the choices selected previously.


The map page is created.


Customizations can be done on the layer properties.  The Pop-ups revealing the attribute values of each point can be edited. Click on the Layer > Pop-ups


Editing can be done on the information displayed on each point (See red boxed area). For the demo- Add no., Address, date established and Repair State are the information preferred for display.


A click on a Point feature on the screenshot to the right displays the pop-up and the edited result.


Style changes are made to the features in the layer. Click Layer Style (cursor finger)


Style Layer window opens on the Left pane. For the Demo, the shape of the Point features with the attribute value 'good' on the repair state field are changed from circle to diamond shape.


The result is seen in the screenshot.


For the demo, both symbols are now changed to the same color.


Click on Share Map (cursor finger) to share the map. This opens a window on the Left pane (red boxed). Fill in the Title, Tags, and Summary details of the map. Check the preferred sharing permisions, for demo, its Everyone (Public).


The User can change the base map. Click on the icon circled in red. A Basemap selector pane opens on the left.


Another good feature for Office is the Copy Map ribbon. Click on the Copy Map, and an image of the map becomes available on the Clipboard.


The Image can be pasted into a PowerPoint slide or even Word document


Thank you for the audience, now let us get to creating and sharing the maps.