Mapping Hacks

Make Your Own Contour Maps #73

Chapter 6, Mapping on Your Desktop

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HACK

in reveals the logic of the contour lines in a way that wasn’t immediately

apparent before. Start another graphics monitor with

d.mon start=x1 and use

d.rast sf_topo to display the original and the shaded topo maps side by

side.

You should play with the azimuth and altitude values provided to r.shaded.

relief to get a sense for the hill shading that’s most visually appealing to you.

Some will definitely look better than others. Read the r.shaded.relief and d.

his manpages for more details. Also, you might want to try using the PNG

driver to output your map to a graphic that you can share with the world

[Hack #75]. Then you should track down the topo maps and elevation data for

your own neighborhood and make your own shaded relief maps!

Hacking the Hack

Of course, picking the azimuth and altitude values out of a hat isn’t good

enough for some people. For the hard-bitten realists among us, there is

another option: you can always input the actual height and direction of the

sun as it’s shining out your window right now (or, at least, where it would

be if it were daytime and not sleeting outside, etc.). Although the r.sun and

r.sunmask tools provided with GRASS will do some of this math for you,

their usage is a little bit complex, and it might be easier to simply get the

angle values from another source.

One option is the NOAA