Mapping Toolbox    
avhrrlambert

Read AVHRR data stored in the Lambert Azimuthal Projection

Syntax

Background

The United States plans to build a family of satellite-based sensors to measure climate change under the Earth Observing System (EOS) program. Early precursors to the EOS data are the datasets produced by NOAA and NASA under the Pathfinder program. These are data derived from the Advanced High Resolution Radiometer sensor flown on the NOAA Polar Orbiter satellites, NOAA-7, -9 and -11 with a spatial resolution of about 1 km. The data from the AVHRR sensor is processed into separate land, sea and atmospheric indices. Land area data is processed to a non-dimensional vegetation index or land cover classification and stored in binary files in the Plate Carree, Goode and Lambert projections. Sea data is processed to surface temperatures, and stored in HDF formats. This function reads land cover data for the continents saved in the Lambert azimuthal projection at 1 km.

Description

[latgrat,longrat,map] = avhrrlambert(region) reads data from an Advanced Very High Resolution Radiometer (AVHRR) dataset with a nominal resolution of 1 km that is stored in the Lambert projection. Data of this type includes the Global Land Cover Characteristics (GLCC). The region specifies the coverage of the file. Valid regions are 'g' or 'global', 'af' or 'africa', 'ap' or 'australia/pacific', 'e' or 'europe', 'a' or 'asia', 'na' or 'north america', 'sa' or 'south america'. Data is returned as a general matrix map with the graticule matrices in units of degrees.

avhrrlambert(region,filename) uses the provided filename.

avhrrlambert(region,filename,scalefactor) uses the integer scalefactor to downsample the data. A scale factor of 1 returns every point. A scale factor of 10 returns every 10th point. If omitted, 100 is assumed.

avhrrlambert(region,filename,scalefactor,latlim,lonlim) returns data for the specified region. The returned data will extend somewhat beyond the requested area. If omitted, the entire area covered by the data file is returned. The limits are two-element vectors in units of degrees, with latlim in the range [-90 90] and lonlim in the range [-180 180].

avhrrlambert(region,filename,scalefactor,latlim,lonlim,gsize) controls the size of the graticule matrices. gsize is a two-element vector containing the number of rows and columns desired. If omitted or empty, a graticule the size of the map is returned.

avhrrlambert(region,filename,scalefactor,latlim,lonlim,gsize, precision) reads a dataset with the integer precision specified. If omitted, 'uint8' is assumed. 'uint16' is appropriate for some files. Check the data's README file for specification of the file format and contents.

Remarks

The AVHRR project and datasets are described in:

http://daac.gsfc.nasa.gov/DATASET_DOCS/avhrr_dataset.html

http://edcwww.cr.usgs.gov/landdaac/1KM/1kmhomepage.html

The Global Land Cover Characteristics dataset of described in:

http://edcwww.cr.usgs.gov/landdaac/glcc/glcc_na.html

The data can be obtained from:

ftp://edcftp.cr.usgs.gov/pub/data/glcc/

This function reads the binary files as-is. You should not use byte-swapping software on these files.

Example

Read the Global Land Cover Characteristics (GLCC) file covering North America in the Lambert projection with the USGS classification scheme. Use the default parameters to read the entire file, taking just every 100th point. This file is available from <ftp://edcftp.cr.usgs.gov/pub/data/glcc/na/lambert/nausgs1_2l.img.gz>.

Read the same file at full resolution for just the area of eastern Massachusetts.

See Also
avhrrgoode
 Read AVHRR data in the Goode projection


  avhrrgoode dcwdata