How to open and work with an .hdf map
Another option is the GDAL tools, if you can deal with the translation of (potentially) 3+D arrays into GIS-alike raster layers. You'd have to build your own rgdal with HDF support on Windows (which is hard), but you can use the GDAL command-line tools that come with an OSGeo4W installation. These pages describe the details and usage: http://www.gdal.org/frmt_hdf4.html http://www.gdal.org/frmt_hdf5.html A default gdal_translate will produce a GeoTIFF which can be read directly by rgdal::readGDAL or raster::raster. I will try your file if I can. Cheers, Mike.
On Fri, Jul 6, 2012 at 8:39 PM, Matthew Landis <landis at isciences.com> wrote:
Marc, It's been a long time since I worked with HDF, so someone out there will likely have better suggestions. But I think you will want to get that out of HDF format as fast as possible. Try using hdp (http://www.hdfgroup.org/hdp.html) to dump the file to a binary or ascii file and then you should be able to read that in to R using readBin or read.delim or such. There are also hdf viewers at the HDFGroup site that should help you to see what the file looks like, figure out the grid, etc. M On 7/6/2012 5:32 AM, Marc Mar? Dell'Olmo wrote:
Hello, I'm trying to open and work with a map I have downloaded from http://glovis.usgs.gov/, obtained from MODIS Terra satellite. This web only allows to download maps in .hdf format. I do not have ArcView, a GIS programme which opens these maps without any problem. I have been trying to do it using "R", however, I have not succeeded... First, I converted the map - which is in version 4 - to version 5 (with h4h5tools http://www.hdfgroup.org/h4toh5). I have tried to open it with satinGet (library satin) but I have obtained this error message: Error en queryname(nom.hdf5, what = "date") : objeto 'date.str' no encontrado Finally I managed to open the file using the function hdf5load (library hdf5). With this function I have obtained two objects "HDF4_DIMGROUP" , "MOD44B_250m_GRID" but I don't know how can I represent spatially the data. I think I have a grid with the values of the variables but I don't know the reference of the coordinates (UTM long lat), the distance between the points of the grid, etc... In general, I don't know how to work with the information... I'm using Windows. Here is the link of the original map, in case it helps. http://dl.dropbox.com/u/22891835/MOD13Q1NDVI_2012Maig.hdf Thanks in advance for the help! Marc
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Michael Sumner Hobart, Australia e-mail: mdsumner at gmail.com