The Recipes

1 Simple xy plot

1/example-small.png Also see full-sized graph and the Gri code

2 Contour Plot, Pre-gridded Data

2/example-small.png Also see full-sized graph and the Gri code

3 Contour Plot, Un-gridded Data

3/example-small.png Also see full-sized graph and the Gri code

4 Salinity Diagram

4/example-small.png Also see full-sized graph and the Gri code

6 World map

6/example-small.png Also see full-sized graph and the Gri code

7 Bathymetry Map with Annotation

7/example-small.png Also see full-sized graph and the Gri code

8 Image Colorscales -- linear graduation

8/example-small.png Also see full-sized graph and the Gri code

9 Image Colorscales -- nonlinear graduation

9/example.png Also see the Gri code

10 Image Colorscales -- GEBCO graduation for maps of ocean/land topography

10/example.png Also see the Gri code

Note: since images are stored in an 8-bit value in Gri, GEBCO color-coding can match inappropriately to contours, in regions of steep topography. The range of depths is 5500m (-5000m to 500m), and with 8 bits this yields a resolution limit of dz=21.5m. Now consider the color transition near 100m depth. The image colours are quantized, with 4*dz being 85.9375 and 5*dz being 107.4m, so that the 100m contour cannot possibly run along the colour transition. This is not a problem if the scale of the chart is large (e.g. the scale of the North Atlantic Ocean), but problems may arise in maps of the continental shelf break. In that case, it's best to modify the image range appropriately, so that it matches the depths more precisely. Thus, you might realize that no depths above 50m were present, or below 2000m; therefore the image range would be 2500m, and the resolution drops to dz=12m, approximately.

11 Geographical map with fancy map projection

11/example-small.png Also see full-sized graph and the Gri code

This example uses the proj unix command. proj is a general and very powerful standalone package, not a standard part of unix. It is available from United States Geological Service at ftp://kai.er.usgs.gov/pub/PROJ.4/PROJ.4.3.3.tar.gz and is also at the much more extensive site http://www.remotesensing.org/proj .

12 Chlorophyll image with SEAWIFS (logarithmic) palette

12/example-small.png Also see full-sized graph, the Gri code, and the palette RGB file.

To get a palette that runs vertically, as opposed to horizontally, do as in this snippet of Gri code.

13 Oceanographic CTD display

13/example-small.png Also see full-sized graph. The code is not available at this time.

14 Gridded bathymetry data, converted to image, then countoured

14/example-small.png Also see full-sized graph and the Gri code.

16 Gridded bathymetry data, converted to image, then countoured

16/example-small.png Also see full-sized graph and the Gri code.

This is a remake of example 14 above, but instead of using a gradual image colorscale, we use a stepped one modified from example 10.

15 Graph-paper style underlay

15/example-small.png Also see full-sized graph and the Gri code.