Saturday, 10 May 2014

S-57 ENC Styling for GeoServer

To get started styling S-57 ENC, I selected a layer of Point geometries from the previously converted S-57 ENC Cell US5FL24M that would be interesting for me to display – WRECKS. This Class actually comes in two flavours -  Point and Area, and we will revisit the latter at a later date.

I proceeded to load in the WRECKS, and it picked up the default point style as shown here:

Looking at the S-52 Specification, WRECKS has two important attributes that affect the styling – CATWRK (Category of wreck) and also VALSOU (Value of sounding). Keeping things simple, I developed an SLD with rules based on the CATWRK values. I also created three graphics based on the designs in the S-52 ENC Symbol Catalog – WRECKS01, WRECKS04, and WRECKS05 using the DAY BRIGHT (more about this later) palette. Loading all that into GeoServer and reloading the layer produced this display:

Some progress, but showing the positions of the wrecks without any further reference to shore is not very useful. I have also simplified these rules somewhat - S-52 actually contains Conditional Symbology Procedures (CSP) - these are essentially rendering rules based on values of attributes and specified using UML Activity Diagrams.

The S-57 Specification consists of over 170 Classes, each of which is presented as one or more Geometric primitives of type Point, Line, or Area (P, L, A) - this could potentially result in several hundred layers and styles. Fortunately, by rendering a small subset of these we can obtain very useful results in an iterative fashion.

Of these 170 or so Classes, there are seven Classes (using Area Geometric primitive only) that make up what is known as the "Skin of the Earth". These are the ENC Group 1 Classes:

LNDARE (Land area)
DEPARE (Depth area)
DRGARE (Dredged area)
FLODOC (Floating dock)
PONTON (Pontoon)
UNSARE (Unsurveyed area)

As an example, Land Area (LNDARE) has Point, Line, and Area. Only the Area Geometry forms part of the Skin. We will look at these next.

1 comment:

  1. Hello Pongsatorn,

    It is very amazing and good work, did you share your sld files on the web or have a plan to share them?