Add documentation for parameter labels

grid_models.md

@@ -25,13 +25,13 @@ Referring to the architecture illustration below:
 * How you collect input data and calculate your results is entirely up to you
 * The results must be presented as a WMS following the VIPS conventions. Scroll down for details.
 
-<img src="illustrations/VIPS-grid-architecture.drawio.png" alt="VIPS Logo"/>
+<img src="illustrations/VIPS-grid-architecture.drawio.png" alt="Grid model workflow"/>
 
 ## Get started
 ### Get gridded weather data
 Gridded weather data typically comes in [NetCDF](https://www.unidata.ucar.edu/software/netcdf/) or [GRIB](https://en.wikipedia.org/wiki/GRIB) format. In VIPS, we have been using NetCDF files, which can be inspected with command-line tools like [`ncdump`](https://www.unidata.ucar.edu/software/netcdf/workshops/2011/utilities/Ncdump.html) and [`ncview`](https://cirrus.ucsd.edu/ncview/). 
 
-<img src="illustrations/grid_models_02.png" alt="VIPS Logo" />
+<img src="illustrations/grid_models_02.png" alt="ncview" />
 
 *`ncview` is a great tool to familiarize yourself with a NetCDF file*
 
@@ -102,6 +102,40 @@ For clients that wish to display the abstract in more than just one block, it is
 </div>
 ```
 
+#### Optional: parameter labels
+Parameter codes are not necessarily self explanatory. E.g. in the PSILARTEMP model; accumulated day degrees are simply called `DD`. To provide labels for these parameter codes in a structured way, we are using an ad-hoc approach to adopting [Microdata](https://en.wikipedia.org/wiki/Microdata_(HTML)). To add a definition, simply embrace the label (in the `wms_abstract` section) with a tag with the `itemprop` attribute, for instance like this: 
+
+```html
+  <p>
+    The warning system model &laquo;Carrot rust fly temperature&raquo; is based on a Finnish temperature-based model (Markkula <em>et al</em>, 1998; Tiilikkala &amp; Ojanen, 1999; Markkula <em>et al</em>, 2000). The model determines the start of the flight period for the 1st and 2nd generation of carrot rust fly based on accumuleted degree-days (day-degrees) over a base temperature of 5,0 &deg;C. VIPS uses the model for the 1st generation only.
+  </p>
+  <p>
+    Standard air temperature (temperature measured 2 m above ground) is used in the model. <span itemprop="DD">Degree-days</span> are defined for this model as the sum of the difference between a base temperature of 5,0 &deg;C and the mean temperature for all days with a temperature &gt;5,0 &deg;C, in other words (daily mean temperature &ndash; 5,0 &deg;C) from 1 March (beginning when the ground has thawed).
+  </p>
+```
+In VIPS-web the label will be visible both in the parameter selector and in the
+location popup.
+
+<img src="illustrations/grid_models_03.png" alt="Illustrating parameter labels" />
+
+**TIP: If you don't have a natural placement for these labels in the abstract text; you can place them in an invisible section, like this:**
+```html
+<!-- Start visible abstract text -->
+<p>
+    The warning system model &laquo;Carrot rust fly temperature&raquo; 
+</p>
+<!-- [..] -->
+<!-- End visible abstract text -->
+
+<!-- Start invisible parameter labels section -->
+<section style="display: none">
+  <span itemprop="DD">Day-degrees</span>
+  <span itemprop="FOOBAR">Foo Bar</span>
+  <!-- etc. -->
+</section>
+<!-- End invisible parameter labels section -->
+```
+
 ### WMS Layers
 In order for VIPS to be able to utilize your WMS, you need to structure the layers in a specific way:
 * The layer names must follow this namespacing pattern: `[MODEL_ID].[PARAMETER ID].[YYYY-MM-DD]`. For instance, the PSILARTEMP (Carrot Rust Fly) model has these layers (for one day):