Layer Configuration

Your Pozi site’s map layers (aside from third party basemaps and imagery layers) are managed within QGIS projects.

Adding Layers

Using your existing QGIS project, you can add new layers to publish them to your users.

1. open your project file in QGIS
2. Layer > Add Layer > pick from vector, raster or other options
3. navigate to source (see note about file paths below)
4. Add
5. Close
6. Project > Save (Ctrl + S)

QGIS Reference: Opening Data

Some common layer configuration tasks you can do in QGIS include:

• change layer name
• filter data
• modify fields

Publish as Vector Layer

Publishing a layer as a vector layer (WFS) enables users to directly interact with features. When a vector layer is turned on in Pozi, every feature from the source dataset is loaded in the browser, including all geometries and attributes. Users can make use of advanced functionality such as searching, filtering, downloading, table view and tooltips.

By default, QGIS Server does NOT expose layers as vectors.

When to Use

Evaluate the pros and cons of using vectors for your layer, and if appropriate, follow the directions below to enable it.

Advantages

• vector layers are fully interactive, enabling users to use the following functionality:
  • search
  • filter
  • report
  • table view
  • download
• when a vector layer is turned on, Pozi loads the entire layer in the browser, including all geometries and attributes. The browser doesn’t need to send further requests to the server every time the user moves the map
• when hovering over a vector feature the cursor changes to indicate the feature is clickable, and a tooltip is displayed with the feature’s title
• vector layers can be used in link-ins

Disadvantages

• the browser can be easily overwhelmed when loading vector layers containing thousands of features, or complex features with many vertices, or tables with a large number of fields, resulting in slow map rendering
• not all QGIS styles are supported in Pozi for vector features
• text expressions for labels are not supported (but you can still make use of virtual fields for creating generating custom label values)

As a broad guideline, don’t enable vector layers for layers that take more than a few seconds to load unless the vector functionality for the layer is essential to your users, and they are happy to wait.

Layers with tens of thousands of features, or very complex features with thousands of nodes, or contain an excessive number of data fields, can often take a long time to load in the browser if enabled as vector layers.

Enable as Vector

1. Project > Properties > QGIS Server > WFS/OAPIF
2. Published: tick on for each layer to be published as a vector layer (or you can click Publish All if all layers are required)
3. OK
4. Project > Save (Ctrl + S)

Layer Name

When you add a layer in QGIS, you can rename it from its original name to a more meaningful, user-friendly name within the QGIS project. Changing the name in QGIS does not affect the source table or file.

Go to Layer Properties > Source > Layer name

Spaces are allowed. To provide users with a better experience, it is recommended to replace any underscores with spaces and use spaces to separate words that may have been combined in the original name.

Styling

Instructions for styling your layers are available on the dedicated Layer Styling page.

Feature Title

When users select a feature from the map, Pozi prominently displays one of the feature’s attributes at the top of the Info Panel as the feature’s title.

The title should be the name of the feature or some other useful information to distinguish the feature from others in the same layer.

You can control which field is used for the layer’s title in QGIS.

Layer Properties > Display > Display Name

This Display Name field is also used fow showing tooltips for vector layers.

Please note that Pozi cannot use the display field if the field name has been given an alias. Consider creating a virtual field with the desired name and use that as the display field.

Selectability

#selectable #queryable #identifiable

To prevent the Info Panel from displaying results from specific layers (say, for imagery layers, or layers configured to display results as a child dataset), update the Data Sources settings in the QGIS project.

Project > Properties > Data Sources > Identifiable > untick to disable layer selectability

It can be useful to make a layer not selectable if it has a corresponding What’s Here dataset to avoid the Info Panel returning duplicate results.

Feature selection link-ins require the layer to be selectable.

Managing Data Fields

QGIS enables you to control what users see of the data without altering the source data.

Hide Fields

By default, all fields from the source data are exposed in Pozi’s info panel. These fields can provide users with a rich set of data to view, query and filter, and some fields are critical for Pozi to correctly display and style the layer (see below).

However if certain fields from the source data are not needed or contain sensitive information, you can prevent QGIS Server from exposing them to Pozi. This will prevent the fields appearing in Pozi’s info panel.

Layer Properties > Fields > select field > Configuration

• tick ‘Do not expose via WMS’
• tick ‘Do not expose via WFS’

Note that any fields required for any of the following purposes must remain exposed via WFS:

• id field for link-in
• id field for link-out
• id field for parent/child joins
• display/title field
• styling (relevant only for WFS layers):
  • field used in categorised or rule-based styling
  • label field

Specify Number of Fields to Initially Reveal

You can limit the number of fields that are initially revealed in Pozi’s info panel. Users can click the Show More button to reveal the remaining fields.

This functionality is designed to make efficient use of the Info Panel space to ensure that important information is not pushed off the bottom of the page. This is particularly relevant when dealing with layers that have related child datasets. By reducing the number of parent fields initially displayed, the user can see the child dataset details without needing to scroll down the page.

Configure the number of fields you want to initially reveal using the following keyword setting:

initialRevealFields=3

If you specify initialRevealFields=0, the Details pane will display in a collapsed state so that no fields are shown. Users will be able to click the pane header to reveal all fields.

Rename Fields

You can make field names more user-friendly by giving your field names an alias.

Layer Properties > Attributes Form > select field > Alias

Please note that Pozi cannot use aliased fields for a feature’s title or tooltip. If you intend to use a renamed field for the feature’s title or tooltip, consider using a virtual field instead of an alias.

Virtual Fields

You can control how your data appears to users without modifying your source data by using the Field Calculator function in QGIS to create virtual fields.

Some use cases for virtual fields include:

• generate a link for a web page or photo by combining a URL string and an ID value
• combine fields (eg first name plus last name, or street address plus locality)
• generate distinct values/classes from ranges to simplify styling or filtering (eg convert a date into a year value)
• perform calculations based on one or more existing values
• generate values based on the feature geometry (eg, length, area)
• do a find-and-replace within text values to change what is displayed to users
• duplicate an existing field, but use a different name (for example, for Pozi to support categorised styling, the target field name must not contain any spaces)

See the QGIS help guide for more information virtual fields and using the field calculator.

Create Link Field

This example shows how to generate a clickable link in Pozi by combining a URL string and an ID value from the data.

1. Layer Properties > Fields > click Field Calculator button
2. tick Create virtual field
3. fill in Output field name with your new field name
4. in Output field type, select Text (string)
5. build expression

Tips for building expressions:

• pick existing fields from the Fields and Values list
• use || to combine strings
• enclose static text with single quotes

The resulting virtual field appears in QGIS and Pozi as if it were standard field.

If the value in the field is a URL (as in this example), Pozi will display it as a clickable link, using the field name as the link text.

If the value is a string ending in .png or .jpg, Pozi will attempt to display the target image inline. Ensure that the string is a valid URL that is accessible by the user.

Imagery Layers

Local

You can add imagery layers such as aerial photos and satellite imagery from local TIF, ECW files, mosaics and other sources to your QGIS project.

Remote

It’s also possible to add layers from an external WMS/WMTS. However keep in mind the following:

• the performance of these layers may be slower than normal due to all image requests being cascaded through the QGIS Server
• if the external WMS/WMTS service is password protected, the credentials must be stored in the QGIS project file - QGIS will prompt to warn that the credentials are stored in plain text, and you must accept that warning in order for QGIS Server to be able to access the service

Exclude Layers

Your QGIS project may contain layers that are not needed for viewing in Pozi. For instance, your project may contain basemap layers that provide context for viewing map layers in QGIS, but you don’t want these to appear in the project’s layer group in Pozi.

To exclude any layers from appearing in Pozi:

Project > Properties > QGIS Server > WMS > Exclude layers (tick) > add > pick layers to exclude > OK

Optional Settings

Other settings can be configured using QGIS Server keyword list. Pozi obtains these settings when it loads and imports each project’s catalogue.

These settings provide an override for some of the default behaviours in Pozi.

Layer Properties > QGIS Server > Keyword list

When using multiple keyword settings, use commas to separate them.

Example:

showLegend=false, visible=true

Table File Maintenance

If you need to move, rename or delete a source dataset from its file location or database, first remove the layer from any QGIS project to which the layer is registered, then save the QGIS project.

You may then attempt to make any changes to the table file(s). If Windows prevents you from making any changes, stop the IIS service that is locking the files.

IIS > (select server) > Application Pools > PoziQgisServer > Stop

You may also need to stop any other services that start with PoziQgisServer.

Restart the service(s) after you make your changes.