Diary of an intrepid office explorer

Remember the good old days? When an explorer would hack off over the sea, through the jungle, or across the desert, armed with little but generous funding from wealthy benefactors, a wind up gramophone and several hundred native bearers? I've been doing the modern equivalent by exploring the island of Sulawesi from the comfort of my own office - using freely available geographic data.

I'll be off the Sulawesi in September to work with VSO on forestry management projects - and must admit to knowing little about the island. As someone working in conservation, hydrology and land use, I'd like to get an idea of what the place looks like, how much it rains, and how warm it is. Pretty much the sort of thing our pith helmetted forebears would be looking for.

To start - what does the coastline look like? Put away the sextant, we'll use this instead:

http://rimmer.ngdc.noaa.gov/mgg/coast/getcoast.html

This is a vector dataset of coastlines of the world, developed from various sources by the US Defense Mapping Agency. Unfortunately, this gives you data in a slightly weird format (text files of [x,y] pairs), which will take a bit of furtling to import into GIS. For the lazy explorer, the same data set has converted to shapefiles by some nice people at the Pacific Disaster Center in Hawaii:

http://www.pdc.org/mde/full_metadata.jsp?docId={32F5F3B8-1CF1-48C5-9B81-57885C0CA448}

There is also a lower resolution shapefile dataset derived from SRTM data here:

http://geoserver.isciences.com:8080/geonetwork/srv/en/metadata.show?id=244

This data set has a 1km resolution, so looks a bit "blocky", but is OK for large scale applications.

Now we'd like some topographic data - information on the land elevation is essential for hydrological modelling. Shuttle Radar Topography Mission (SRTM) is not the best accuracy (a few metres vertically) or resolution (90m, or 30m over the US), but it's probably OK for hydrological modelling in some places, and gives you easily accessible, near global coverage.

http://www2.jpl.nasa.gov/srtm/

A bit of faffing around with gdal will give you a DTM (Digital Terrain Model) referenced to your projection of choice (UTM zone 50S for west Sulawesi).

Finally, we'd like to know how wet it is - will I need to take an umbrella? WorldClim has a global datasets of rainfall, temperature and other climate variables at 1km resolution:

http://www.worldclim.org/

This is interpolated from climate station data - so the accuracy must be suspect where measurements are sparse.

Here are the results:



Coastline and SRTM topography Mostly volcanoes, with dendritic drainage patterns superimposed.





















Mean January Rainfall - note how the rainfall varies strongly with topography and coastal aspect, especially in the South Sulawesi peninsular.























So, 170 000 square kilometres of the east indies mapped without leaving the office. Leaving me time for a snifter before lunch at the Reform Club. Cheers!