Where is it?

A guide to finding your place in the GeoCover data set.

The GeoCover data,while presenting imagery of the Earth's surface, does not indicate where something, or some place, is located.

There are several solutions to this problem.

First, if you need to find the latitude and longitude of a place of interest, consult a gazetteer. A gazetteer is a geographical index listing names and locations, usually listing the locations as latitudes and longitudes.  There are two sources of such gazetteers on the Internet.  

For places in the United States and Antarctica, the source is the United States Geological Survey (USGS) at URL:

http://geonames.usgs.gov/index.html

This gazetteer is available for query on the web, or you may download the data via FTP (via the "download data" link) and use them later.  If you are downloading files for future use, download either the ones with the "XX_deci" ending (where XX is the 2-letter abbeviation for the state), or download the "yyyy" files, where yyyy is the state name.  Both types of files are text files (*.txt files) and either type should work.

For other areas of the world, go to the National Imagery and Mapping Agency's (NIMA's) web site at:

http://164.214.2.59/gns/html/index.html

NIMA uses 2-letter abbreviations for country files (the abbreviations are standard, and their documentation is on the NIMA web site.).

The NIMA web site will also give you the choice of entering a query on the web site or downloading a database via FTP (unzip them after you download them).

Having found the latitude and longitude of the place you are searching for, you may go to the US Digital LandsatMosaic viewer included with the U.S. GeoCover data set and load the tile you need (it is assumed that you can determine which tile you need).  Move the cursor until the readout in the lower left-hand corner is the longitude and latitude you desire. Then click on the mouse button to zoom in on the location sought.

If you are using a viewer that does not present the latitude and longitude, but rather presents the coordinates in the Universal Transverse Mercator projection (UTM) described in the Introductory Landsat Tutorial, you must include another step.  You must transform the latitude-longitude into UTM coordinates of zone, easting, and northing. Many latitude-longitude to/from UTM converters are available on the web.  One called llutm is incapsulated in "llutm.zip" and  can be found at:  

ftp://ftp.blm.gov/pub/gis

Unzip llutm.zip and

run the executable  llutm.exe (it will run in a DOS window)

An alternative approach is to use the Excel spreadsheet called "ll_utm.xls" attributed to the Sicilian Rhyolite Society at Sul Ross State University (included in this directory).

After converting your location into UTM coordinates (zone, easting, and northing),  load the appropriate tile into your viewer (e.g., the MrSID GeoViewer from Lizardtech), set the cursor to the appropriate UTM coordinates, and zoom in.  Note that most viewers list only the eastings and northings, but not necessarily the zone. The name of each GeoCover data tile indicates the zone.  Some examples are:

N-30-50:  Zone 30, northern hemisphere, 50-55 degrees North Latitude (England)

S-56-30:   Zone 56, southern hemisphere, 30-35 degrees South Latitude (Australia)   

Another way to find your place is by searching on the place name.

It involves adding a gazetteer to the GeoCover imagery as an overlay.  Free software that does this is available from the USGS as dlgv32Pro.  Unfortunately, it is only available for PC-type computers running Windows.  Download it from: 

http://mcmcweb.er.usgs.gov/drc/dlgv32pro/

After installing it on your computer, start it, and then open a GeoCover tile using:

 "File" > "Open as new"

Note that when you load a GeoCover tile that is not in the USA set (you can find and download them from http://zulu.ssc.nasa.gov/mrsid), you may have to identify the UTM Zone for the tile (on the drop down Zone menu, scroll to the appropriate zone and click on it) and identify the datum to use (on the drop down Datum menu, scroll down to and click on "WGS84"). The default Zone is UTM zone 15, northern hemisphere, and the default datum is NAD83.  You need to change both. Leave the "Projection" on "UTM" and the "Planar Units"on "Meters". Otherwise, dlgv32Pro is lost and the GeoCover image and the corresponding gazetteer may not overlay one above the other.

Note: You can display either UTM coordinates, latitude-longitude(geographical) coordinates, or no coordinates at all on the image using:

 "Tools" > "Configure...",

  then click on the "General" tab, and

  check the button you want in the "Grid Display" box near the bottom.

Now that you have the GeoCover data in the dlgv32Pro window, you need to add a gazetteer file.  

To add a USGS gazetteer file:

You must first download the file(s) for the state(s) you want from the above web site and unzip it(them) into a directory on your hard drive.  Either of the two forms will work - XX_deci.txt, where XX is the two-letter abbreviation for the state, or state-name.txt.

Click "File" (upper left hand corner of your screen), then

"Open into current..." (NOT "Open as new"), and then 

 identify the gazetteer file to load

Another box will appear asking which format.  Double click on "GNIS" for the USGS state files.

To add a NIMA gazetteer file:

Add the NIMA gazetteer file the same way you did the USGS gazetteer file - use:

"File" > "Open into current..", etc.

You probably will NOT be asked which format to use.

In either case (foreign or domestic), dlgv32Pro will then load the gazetteer and superimpose the points and icons on top of the GeoCover image. The area covered by the gazetteer will probably be blackened with information.  

To find the location you want,

Click on the "Search" button on the tool bar and

Enter the name of the place you want to go to.

A window will appear with matches - there may be many.  For example:

Someplace
Someplace Airport
Someplace General Hospital
Someplace Park

Double click on the name you want.

The image will move and center over that location.

To zoom into that location without moving the image and loosing your place:

Click on the magnifying glass with the red cross (or plus sign) in the circle (it's the leftmost magnifying glass on the toolbox).

Keep clicking until you zoom in far enough that the labels spread out and you can see the GeoCover data underneath.

If you want to back away without moving the image, click on the magnifying glass with the red minus sign.

Note:  You can hide the gazetteer names and icons by dropping down the "control center"  (third button in on the left of the toolbar), highlighting the gazetteer line, and clicking on "Hide Overlay" button.  You can also bring the gazetter information back to the screen using the control center and the "Show Overlay" button, or delete it from the data sets that you have open via the "Close Overlay" button.

Once zoomed in, you can use the search function ("Search" button on the toolbar) to move to another location without backing out.

You can move around the image by clicking on the button between the zoom in/zoom out button and the button with the ruler on it - the one that looks like a funny-looking cross with arrows.  Move the symbol to where you want to re-center the image, and left-click.

You can have up to a total of 4 data sets (MRSID files and/or gazetteer files - or other files) open at any one time in dlgv32Pro.

Good hunting!  Have fun!