Optimizing Maps, tips and tricks

• As test_user1 view the Boulder map and click on the layer menu in the top-left corner.

  

• Expand the datasets list and highlight the Mainrd one. Click on the property tool

  

• Switch to the view options tab, you will notice a few settings that can be tweaked on each dataset to improve the map quality or rendering speed

  • Format: This allows us to set the output media type from the ones supported by the spatial service.

  • Tile Size: This value is usually set to 256x256 pixels, GeoNode sets them to 512x512. This value allows us to send tiled requests to the Tile Service. A larger size allows GeoNode to reduce the number of requests per dataset.

  • Visibility Limits: Has the same effects as the Scale Denominator rules on the styles. The two options are always applied independently.

  • Transparent: When enabled, it allows the server to render the alpha transparent channel where no data is present.

  • Use cache options: decides whether or not to use the tile service (WMTS) or (WMS).

  • Single Tile: When enabled GeoNode won’t create tiled requests for this dataset but will create a single tile with the dimensions of the current viewport. In some cases, this might speed up the rendering by drastically reducing the number of requests. Be aware that Single Tile will never use the server cache.

  

• For this dataset, let’s change the output format to jpeg+png8 and set the Min Scale to some value to hide the dataset at higher zoom levels.

  

  The JPEG+PNG8 output format will allow GeoServer to use JPEG compressions on images and PNG8 on transparent tiles. This will reduce the size of the images, speeding up the dataset, but it will also reduce its quality. That option is typically only useful on raster imagery.

• You can also edit other available datasets:

  • Change the output format to PNG8, on vectorial datasets with few colours (like in the above case). This will greatly reduce the size of the images, resulting in an overall speedup of the dataset.

  • Open the Network tab of the browser and inspect the ows requests. Notice the different output formats of the requests for the dataset. Do some tests by changing the output format, and notice the difference between the sizes and timings of the outcomes.

  • Also, by expanding the Headers section, you will see how the geowebcache responses match with a Cache HIT, meaning that we are correctly asking for cached tiles to the WMTS service

It is also possible to select and edit the default style of a dataset from a map by clicking on the dropper icon as shown below.

• When changing the settings for datasets on a map with many overlays, it is good practice to temporarily deactivate the other layers to speed up the work by avoiding loading all of the layers every time

• Let’s edit the options for the Mainrd dataset. Click on the Filter option, and check the Area of Interest options

• Change the Filter Type to Polygon, and the Geometry Operation to Contains. Draw a polygon on the map and click Apply

  

• Try modifying the Geometry Operation to Contains and note the differences

  

• Save the filter and go back to the map. Notice that a small filter icon now appears near the dataset name, and the map only shows the filtered features

  

• You can optionally persist the changes on the map.

Attributes Media Types Rendering on GetFeatureInfo

The GetFeatureInfo is a special operation in the OWS protocol that allows us to query a dataset on a specific position to get back the values stored on the backend.

In the case of a VECTORIAL dataset, the outcome of the GetFeatureInfo is basically a set of records (i.e. key-value pairs where the keys are the attributes from the schema below).

In the simplest use case, the outcome of the GetFeatureInfo is a plain text report of the list of attributes along with the values of that specific location. As you can imagine, the values can be almost anything, even references to external links or media contents (like images, videos or audios).

GeoNode can also apply, eventually, an HTML template to the GetFeatureInfo outcome. That means that GeoNode can render the output as HTML content.

From the dataset metadata, there’s the possibility to edit such a template. In particular, there are two different ways to enable it:

1. Basic: GeoNode will present the available attributes list, allowing the user to change the order, visibility, and media-type on each attribute.

2. Advanced: GeoNode will present a rich-text editor panel allowing the user to define its own custom HTML template.

In this section, we will see how the basic one works by defining and editing a new empty dataset.

• Let’s first create a new empty dataset with the following attributes:

  • geometry type: Polygon

  • image: String

  • video: String

  • audio: String

  • href: String

  

• Edit the layer data and add a new polygon

  

• Fill the attributes with some links, e.g.

  • image: https://asia.olympus-imaging.com/content/000107506.jpg

  • video: https://www.youtube.com/watch?v=-ucUFBTUYLI

  • audio: https://samplelib.com/lib/preview/mp3/sample-3s.mp3

  • href: https://geonode.org/

  

• Save, click on the polygon, and look at the results

  

• Now go back to the dataset details, edit the metadata, and move to the Attributes tab. Change the contents as shown in the figure

  

• Save, visualize the dataset, and click on the polygon again

  

  

Next Section: Charts and Widgets