Horizontal slices

A profile file can also hold a horizontal slice: a map of the data at a fixed depth. The picker recognises the type of profile when it loads the file and adapts the window.

What changes

	Vertical profile	Horizontal slice
profile axis	distance along the profile (km) × depth (km)	longitude × latitude, with the depth of the slice as title
aspect ratio	free	a degree of longitude is drawn cos(latitude) times as long as a degree of latitude, so the map is not distorted
topography axis	above the profile	hidden
topography	line in the topography axis	heatmap or contour lines on top of the volume data
volume data fields	fields of the volume data	in addition, the depth of each surface data set (<name>: depth)
surface data	lines along the profile	contour line where the surface crosses the depth of the slice
point data	projected onto the profile	at their longitude and latitude
map overview	line from A to B	box around the slice, labelled with its depth
picks	x and depth	longitude and latitude

Topography on a horizontal slice

The topography panel of a horizontal slice has:

Control	What it does
data set dropdown	Only if the profile has several topography data sets: which one to show.
mode dropdown	Heatmap: the topography as a semi-transparent heatmap (colormap oleron, centred on sea level). Contours: contour lines of the topography. Off: no topography.
opacity slider	The opacity of the topography heatmap. Lower it to see more of the volume data below.
Contour levels	The elevations of the contour lines, for example 0 for the coastline (the default) or -2, 0, 2. Press Enter.

Picking on a horizontal slice

Picking works as on a vertical profile (see Picking), but the picks are positions on the map. In a saved pick file:

• lon and lat hold the picked position,

• depth holds the depth of the slice for every pick,

• x is NaN (there is no distance along a profile),

• the metadata hold the depth of the slice instead of start and end coordinates.

Load Picks only accepts picks that were made on a horizontal slice at the same depth.