20090618

WORLDCLIM Data

All WORLDCLIM data for Tanzania (Zone 36 and 37) downloaded and imported in GRASS.

WorldClim is a set of global climate layers (climate grids) with a spatial resolution of a square kilometer. The current version is Version 1.4 (release 3).

Some notes: tiles are in Generic grid (raster) format. EPSG:4326. Spatial resolutions: 30 seconds (0.93 x 0.93 = 0.86 km2 at the equator). Data files (.BIL) are sequential binary files in which values are stored line by line from the upper-left to the lower-right corner. Each cell (pixel) is an integer value (2 bytes; -32768..32767). If you simply open the data as images or raster data sets, there is a problem. ESRI software assumes that BIL files do not have negative values. These values (x) are replaced by (65535 - x); E.g., -10 becomes 65525. The nodata value of -9999 is not recognized... a BIG mess results... I got the same problem with GRASS. For a workaround:
Use DIVA-GIS (free download)
Data\Import to gridfile\Multiple Files (BIL/BIP/BSQ) and then
Data\Export to gridfile\Multiple Files (ESRI Ascii)
Now GRASS works, with module r.in.arc. Or Qgis GRASS plugin, r.in.arc module.

Informations are:
tmean = average monthly mean temperature (°C * 10)
tmin = average monthly minimum temperature (°C * 10)
tmax = average monthly maximum temperature (°C * 10)
prec = average monthly precipitation (mm)
bio = bioclimatic variables derived from the tmean, tmin, tmax and prec
alt = altitude (elevation above sea level) (m) (from SRTM)

Note that temperature is expressed as degree C * 10.

BIOCLIM
Bioclimatic variables are derived from the monthly temperature and rainfall values in order to generate more biologically meaningful variables. These are often used in ecological niche modeling (e.g., BIOCLIM, GARP). The bioclimatic variables represent annual trends (e.g., mean annual temperature, annual precipitation) seasonality (e.g., annual range in temperature and precipitation) and extreme or limiting environmental factors (e.g., temperature of the coldest and warmest month, and precipitation of the wet and dry quarters). A quarter is a period of three months (1/4 of the year).
They are coded as follows:
BIO1 = Annual Mean Temperature
BIO2 = Mean Diurnal Range (Mean of monthly (max temp - min temp))
BIO3 = Isothermality (P2/P7) (* 100)
BIO4 = Temperature Seasonality (standard deviation *100)
BIO5 = Max Temperature of Warmest Month
BIO6 = Min Temperature of Coldest Month
BIO7 = Temperature Annual Range (P5-P6)
BIO8 = Mean Temperature of Wettest Quarter 
BIO9 = Mean Temperature of Driest Quarter
BIO10 = Mean Temperature of Warmest Quarter
BIO11 = Mean Temperature of Coldest Quarter
BIO12 = Annual Precipitation
BIO13 = Precipitation of Wettest Month
BIO14 = Precipitation of Driest Month
BIO15 = Precipitation Seasonality (Coefficient of Variation)
BIO16 = Precipitation of Wettest Quarter
BIO17 = Precipitation of Driest Quarter
BIO18 = Precipitation of Warmest Quarter
BIO19 = Precipitation of Coldest Quarter

This scheme follows that of ANUCLIM, except that for temperature seasonality the standard deviation was used because a coefficient of variation does not make sense with temperatures between -1 and 1).

Links:
WORLDCLIM Docs:
http://www.worldclim.org/methods.htm
http://www.worldclim.org/format.htm
http://www.worldclim.org/bioclim.htm
DIVA-GIS
WORLDCLIM Data:
http://www.worldclim.org/tiles.php




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AFRICOVER Data

All AFRICOVER data for Tanzania downloaded and imported in GRASS:

    •    tz_boundaries
    ⁃    tz_politicalboundary
    ⁃    tz_adm

    •    tz_towns
    ⁃    tz_majortowns
    ⁃    tz_othertowns

    •    tz_roads
    •    tz_rv
    •    tz_landform_agg
    •    tz_lithology_agg
    •    tz_spatial_agg 
    •    tz_cultiv_agg      
    •    tz_grass_agg
    •    tz_woody_agg

All vector in shape format, EPSG:4326. No problem with GRASS Qgis plugin, Module v.in.ogr.qgis.
Database uses sqlite driver, set up by GRASS Qgis plugin, Module db.connect.
AFRICOVER.sqlite created BEFORE importing data, with sqlite-manager extension for firefox.

Links:

AFRICOVER: http://www.africover.org/
Sqlite-Manager: http://code.google.com/p/sqlite-manager/
Mozilla Firefox: http://www.mozilla.com/en-US/

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SRTM DEM

All SRTM tiles for Tanzania downloaded and imported in GRASS (EPSG:4326):

42_13 | 43_13 | 44_13
42_14 | 43_14 | 44_14
42_15 | 43_15 | 44_15 |45_15

All tiles patched by:
r.patch input="srtm_42_13,srtm_42_14,srtm_42_15,srtm_43_13,srtm_43_14,srtm_43_15,srtm_44_13,srtm_44_14,srtm_44_15,srtm_45_15" output="srtm_full"

Links:
SRTM (Original dataset Docs): http://www2.jpl.nasa.gov/srtm/index.html
SRTM (V4): http://srtm.csi.cgiar.org/

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Updates

Switched to:
  • GRASS 6.4 RC5
  • Qgis 1.1.0
QGIS/GRASS and Frameworks Mac binaries: http://www.kyngchaos.com/software:unixport




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