blog.remotesensing.io

Written by charlie   
Friday, 31 October 2014 14:23
This morning, I found a site dedicated to geospatial analysis that I thought I would pass along.  It illustrates the broad range of applications that remote sensing can be used for, and how to best work with large datasets.  Although postings are sporatic, it is now bookmarked as one of my "GDAL goto" sites since it offers great ideas, approaches and tips on analyzing GIS data.
The  post about publishing 3D DEM's online immediately caught my attention. I have been considering displaying a  3D NVIZ DEM created in GRASS GIS online, but couldn't determine the best way to get it done; this looks like a reasonable workaround.
The posts Using GDAL with Python: a basic introduction is something that I have yet to attempt, but am looking forward to learning more about. Also there is a helpful post about Installing GDAL on Ubuntu , which admittedly, is better than my own.
Enjoy.
 
 

Winterberry

Written by charlie   
Wednesday, 29 October 2014 11:43

The hardy, deciduous shrub, Winterberry (Ilex verticillata) is a species of Holly native to the US, found East of the Mississippi ranging from Alabama to southern Canada, in swamps, wet woods and other areas with evenly moist, acidic soil.  Ranging in size from 8 to 12 feet in width and height, the Winterberry is also used in gardens as a cheery winter ornamental, thriving both in rain gardens and dryer soils, hence its Facilitative Wetland designation of "Usually occur in wetlands, but may occur in non-wetlands".   Winterberry propagates both by suckering and flowering.  As with the Spicebush, at least one male plant must be planted within pollination distance to females for them to bear fruit. Unlike the evergreen Holly, the Winterberry's leaves turn black at first frost and entirely loses it leaves -making its clusters of red berries even more striking on bare branches in the early winter.

Beyond its utility as an important source of food for nearly 50 species of birds and small mammals, its berries and branches are also used for fall wreathes and flower arrangements.  In the Berkshires, Massachusetts garden centers sell a small bouquet of  Winterberry for $7 - a well filled 5 gallon bucket is around $30  - you can even pick your own.

Visit the gallery page at the Lady Bird Johnson Wildflower Center for some great photos of the plant and berries.

Sources and Further Reading:

http://plants.usda.gov/core/profile?symbol=ilve

http://pss.uvm.edu/ppp/articles/winberry.htm

 

http://www.wildflower.org/plants/result.php?id_plant=ILVE

 

Amazon AWS and GDAL

Written by charlie   
Monday, 27 October 2014 02:14

The Geospatial Data Abstraction Library or GDAL, (http://www.gdal.org/) is the trusty, open source, Swiss army knife of geoprecessing software, providing behind the scenes muscle to many GIS programs, Grass GIS, QGIS and Geoserver included.

Wanting to merge 9 raster maps using gdal_merge.pyto model a watershed, I realized it was not natively available in Grass GIS. Having both a production server running Geoserver and content with my Grass GIS setup on my laptop - I was hesitant to install GDAL on either platform, it has a reputation for being difficult to install, and lacking the confidence to repair any dependency errors - I had two options.

I could have either pulled an oldlaptop out of storage and do a fresh Ubuntu install, orstart a Small (T1) Ubuntu instance through Amazon AWS (aws.amazon.com), install GDALand start and stop the instance it as needed. Taking the AWS route, it took less effort and time than expected. As an added bonus, the instance can beexpanded asneeded to process large datasets - try that with a clunker laptop running 2GB of memory.

Through the AWS Admin panel, I createda Small (T1) Ubuntu Trusty- 14.04 instance. Installing GDAL was painless, for my needs, it required both the GDAL installation plus Python, installed by using apt-get as follows:

sudo apt-get install libgdal-dev

sudo apt-get install python-gdal

Verify that gdal is installed and version by using:

gdal-config –version

After uploading and changing permissions of the files I needed to merge with gdal_merge.py, I ran the script, using thistimesaving tip, which will merge merge all files in the current directory with the .tif extension, as follows:

gdal_merge.py -o output.tif $(ls *.tif)

It took all of 30 seconds to merge all 9 files, and after processing the file was downloaded and worked correctly.

Additional Reading and Resources

Manual page forgdal_merge:http://www.gdal.org/gdal_merge.html

Manual page forgdal-config: http://www.gdal.org/gdal-config.html

http://www.sarasafavi.com/installing-gdalogr-on-ubuntu.html

https://gis.stackexchange.com/questions/116740/gdal-merge-py-on-ubuntu-many-tif-tiles-into-one/116770#116770

http://skipperkongen.dk/2012/02/21/pointers-for-gdal-and-python/

 

https://gis.stackexchange.com/questions/116740/gdal-merge-py-on-ubuntu-many-tif-tiles-into-one/116770#116770

Last Updated on Wednesday, 29 October 2014 11:55
 
 
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