EVS-Islands

FREE Global Orthorectified Landsat Data via FTP

I was working on a cloud covered island and figured there must be better imagery available. I am keenly aware that Landsat imagery is freely available. I typically work with Landsat ETM+ mosaics. The other way one can work with this imagery is using WRS-1 or WRS-2 sorted images. The trick is, you have to identify a Path and a Row - not necessarily the easiest task. Then I stumble across the above web site. You can snag all of the WRS images (circa 1970, 1990 and 2000). They also provide a link to a USGS Path/Row calculator. You enter a lat/lon and the applet calcultes the Path/Row. It is a slick interface. Once you know your areas Path/Row, then visit the ftp and download to your heart's content. I'll give you a step-by-step on how to get this free imagery.

(Some of you experienced "image hogs" might find the following obviously simple. I, on the other hand, think my audience appreciates a step-by-step guide. And since it is my site, I'll do what I want. Hope some of you find this helpful.)

This is the entry page for Landsat.org. It is here that you are linked to the path/row calculator and all of the image files.

This is the USGS path/row calculator. You enter your target areas lat/lon and the calculator determines the Landsat path/row of your images.

At the Landsat.org entry page select the range of paths your specific path is located in (WRS-2 Path 049-088).

Now you select your specific path (049).

Now you select your specific row (066).

This is your file (p049r066 7x010104).

If you want, select the jpg file and you can view a small picture of your image.

These are the files that you are able to select from. The images, except for the jpg, are tif files. They are compressed (zipped) and you will need to unzip them when you get them downloaded before using them. My digitizing/mapping software, Global Mapper, allows me to load zipped files. Once loaded, I can work them. Nice option. (I want to add - I know there are excellent mapping packages that match and often exceed the range of capabilities offered by GM. ESRI, the premier mapping package is one that comes to mind. However, GM offers a free trial and if you like it, it costs $199.00. That is big bucks for me. I am a software tightwad. I have not once regretted the $199.00 initial investment. I have purchased a major upgrade for $90. The sweet aspect about GM is it is simple, simple, simple to use. Loading map files or images is a snap. The tools are quick to learn and intuitive to use. But the absolute best feature is Mike. He is GM! Mike is programmer, problem solver and knowledge source extrodinaire. Mike makes GM a great investment. Whatever the problem, email him and he will respond within hours, often minutes. If the problem is in his software, he will fix it and send out a repaired version (no charge). For my bucks - GM is a solid package for digitizing from satellite imagery. 'nuf said. (No, I don't get a kick-back from GM - I just like it.)

This is a WRS-2 image, still zipped, about to be loaded into Global Mapper.

The image is loaded and I have selected my work area to zoom into.

Now I can select my tool to work with and begin digitizing.

OT: Data

Posted by Mr Minton on Sunday, May 07, 2006 at 5/07/2006 03:05:00 PM | Permalink