Differentiating between land and water¶

To add simple land- or water-masks to your figures, you can use the watermask() method in the main Nansat class. Download the prepared MODIS 250M water-mask product from our server and add the path to the directory with this data to an environment variable named MOD44WPATH (e.g. MOD44WPATH=/Data/sat/auxdata/mod44w).

Distance to the Nearest coast¶

To get inforamtion about distace to the nearest coastline within the domain of interest, you can use distance2coast method from the nanasat.toolbox. Download NASA’s Ocean Biology Processing Group `0.1x0.1 degree Distance to the Nearest Coast product <https://oceancolor.gsfc.nasa.gov/docs/distfromcoast/GMT_intermediate_coast_distance_01d.zip`_ and add the path to the directory with this data to an environment variable named DIST2COAST (e.g. DIST2COAST=/path/to/file). For more inforamtion about the product wisit NASA’s Ocean Biology Processing Group <https://oceancolor.gsfc.nasa.gov/docs/distfromcoast/>.

Digital Elevation Models (DEMs)¶

Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010)¶

The GMTED2010 datasets are provided by the U.S. Geological Survey. We have prepared a GDAL vrt file that can be used together with mapper_topography.py to open the 30 arcseconds Digital Elevation Model (DEM) with Nansat. To use it, the vrt file must be downloaded from ftp://ftp.nersc.no/nansat/dem/gmted2010_30.vrt and stored in the same folder as the tif files of mean elevation available at https://edcintl.cr.usgs.gov/downloads/sciweb1/shared/topo/downloads/GMTED/Global_tiles_GMTED/300darcsec/mea/.

In case you want to use a different DEM, the procedure is as follows:

Download the relevant GDAL readable files to a local folder
Generate a vrt file using gdalbuildvrt, e.g.:
```
gdalbuildvrt gmted2010_30.vrt *.tif
```
Update mapper_topography.py to accept the new kind of file(s)

Global 30 Arc-Second Elevation (GTOPO30)¶

We have also created a vrt-file for the GTOPO30 dataset. This is available as ftp://ftp.nersc.no/nansat/dem/gtopo30.vrt. The vrt-file should be placed in the same folder as the .DEM files available at https://dds.cr.usgs.gov/srtm/version2_1/SRTM30/.