Steps to Using the Downloaders

Step 1: Decide on What Data is Needed

Downloadable Raster Files
Symbol Name Description
Ground Resolution
Paper Resolution
Digital Orthophoto Quarter Quadrangles
Aerial photography. Not tonal balanced. Acquisition date is first quarter 1998.
1 meter

1:24,000 DRG

USGS 1:24,000 Scale
(7.5 minute)
Topographic Maps
Scanned map. Not edge matched.
1 in = 24,000 in or 2,000 ft 
1:24,000 DEM USGS 1:24,000 Scale
(7.5 minute)
Digital Elevation Models
Digital elevation data in the USGS DEM format.     No
1:100,000 DRG
USGS 1:100,000 Scale Topographic Maps
Scanned map. Not edge matched.
  1 in = 100,000 in
1:250,000 DRG
USGS 1:250,000 Scale
(Quarter Million Scale)
Topographic Maps
Scanned map. Not edge matched.
  1 in = 250,000 in 

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Step 2: Enter the Appropriate Downloader

Enter one of the downloaders by clicking on its title from the Raster Downloader page. The four choices are DOQQ, 1:24,000, 1:100,000, and 1:250,000.

Once inside, the downloader will display a map of the state of Louisiana. The statewide map shows the boundaries of the parishes, major roads such as interstates and U.S. highways, and the names of major cities in the state. For the 1:100,000 and 1:250,000 downloaders, the names and boundaries of the quadrangles are shown over the base map. The image below shows how the DOQQ downloader appears when you first enter it.

The dark green areas of Louisiana indicate that DOQQs are available for downloading. The dark gray areas of the state indicate that the DOQQs are not available for downloading. All the downloaders follow this system of coloring the quadrangles that are available for downloading or not. In the map above, only the DOQQs in and around the Calcasieu Parish area are available for downloading. As more DOQQs become available for the state, this map will change from mostly gray to mostly green.


Each downloader uses Intergraph's GeoMedia Webmap to display a live index map of the state to help guide in your selection of which quadrangles you wish to download.
Visit Intergraph's GIS Website


The map that is generated is a Web map. It is a CGM file (for Windows users) or a JPG file (for non-Windows users). It is an active map. As you zoom into the map, other features will turn on. Quadrangle boundaries, quadrangle names, community boundaries, community names, and DOQQ boundaries will appear as you zoom close enough into the maps.

This image to the right shows a tooltip for Cameron Parish. By moving the cursor over the parishes, tooltips appear to show the names of parishes or quadrangles.

Notice that the quadrangles are not showing. For the DOQQ and 1:24,000 downloaders, due to their number, the quadrangles would cover and blot out the parishes, roads, and other features of the map. Zooming into the map by clicking on the zoom in buttons or by clicking on a parish will cause the quadrangle boundaries to appear.

The image to the right shows the state map for the 1:100,000 downloader. Because there are fewer of them, the quadrangles are shown upon entering the downloader.

Notice that the quadrangles available for downloading are in dark green. The quandrangles in dark gray are not downloadable.

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Step 3: Find the Desired Quadrangle(s)

1) Search by Attribute

One way is to use some attribute of the quadrange such as its name or code number. At the top of each downloader, there are two fields. One field allows for the selection of an attribute upon which to search. The second field allows you to enter the value of that attribute. As an example, below is the attribute search part of the DOQQ downloader.

First, select which of the attributes from which you wish to search from the attribute pull-down list.

Second, in the text box, type in the value of attribute for which you want to search. You can use the * as a wildcard. For example, to find the Bogalusa quadrangle, you could type Bog*. To find all quadrangles beginning with the letter C, type "c*". The search is not case sensitive, that is, you may use upper and lower case characters. However, IT IS SENSITIVE to spaces, so place only one space between words.

Click on the submit button or press return to activate the search.

The quadrangles that meet your selected attribute will be listed to the left of the map. The image to the right shows the listing made by you clicking on the LIST button beside the map. For each quadrangle, its name and some other attributes are listed. You can zoom directly to a quadrangle by clicking on its link in this listing. Also, there is a center button that allows for the map to be centered on that quadrangle. (The map will not zoom to the quadrangle just center upon it.)

The the case of the DOQQ downloader, both the DOQQ name and its corresponding 1:24,000 quadrangle are linked. You are able to zoom to the DOQQ or to the 1:24,000 quadrangle containing the DOQQ.

2) Search by Navigating on the Map via Map Buttons

Another way to find a quadrangle is to nagivate on the map. You can zoom into, zoom out of, or pan around on the map provided with the downloader. A table of the buttons is to the right..

The Redisplay State Map allows you to start over. It zooms to the starting point where the entire state is shown.

Although the LIST button is not really a nagivation button like the others, it allows you to list the quadrangles that appear on the map. From the list, you can make the map zoom directly to a quadrangle by clicking on the name of the quadrangle in the list or center upon the quadrangle without zooming by clicking on the center button..


The CENTER button (which looks like a target) appears not beside the map but under each quadrangle listed. This button causes the map to move so that the quadrangle becomes the center of the map. The map will not change scale.

Symbol Name Description
Clicking on one of the +'s allows you to zoom closer into the center of the map.
Clicking on one of the -'s allows you to zoom farther away from the center of the map.
Pan left or west
Clicking on one of the arrows allows you to pan (move) to the left or westward.
Pan right or east
Clicking on one of the arrows allows you to pan (move) to the right or eastward.
Pan up or north
Clicking on one of the arrows allows you to pan (move) upwards or northward.
Pan down or south
Clicking on one of the arrows allows you to pan (move) downwards or southward.
Redisplay state map
This button redisplays the initial map with a statewide view. The button also reestablishes a Webmap session that has expired.
List all quadrangles in current map
This button lists all the quadrangles that are in the current map. Even if you are zoom out where the quadrangles are not displayed, this button will list them in the listing window on the left.
Center on quadrangle
This button centers the map on the quadrangle. The map does not change scale, that is, the map does not zoom in or zoom out. This button is found under each quadrangle listed on the left side of the downloader.

3) Search by Clicking on Parish

For the DOQQ and 1,24,000 downloaders, the individual parishes are active. As you move across a parish, the name of that parish will appear as a tooltip. If you click on the parish, the map will zoom into that parish. The boundaries of the quadrangles will appear. (For the DOQQs, you may need to zoom in some more before the boundaries of the DOQQs appear.) .

The image to the right shows the map after you have clicked on Washington Parish. As you move across the map, the names of the quadrangles appear as tooltips. You can click on any quadrangle so that it is listed on the left side of the screen. Also, if you click on the LIST button on the left side of the map, all quadrangles in the map are listed.

The image to the right shows the map after you have zoomed into the map enough that the DOQQ boundaries appear. In this example, the DOQQs west of Lake Charles are appearing on the map. Notice that the tooltip shows the name of the Moss Bluff NW DOQQ. You can now click on any DOQQ so that it is listed on the left side of the screen. Also, if you click on the LIST button on the left side of the map, all DOQQs in the map are listed.

The three methods can interact with one another. You can do a search based upon an attribute and then use the buttons to navigate around. The map to the right was generated by first looking for 1:24,000 quadrangles with a name of "Bat*" Then the map was zoom out slightly.

Notice that when you are zoomed into the map sufficiently, community names and boundaries appear.

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Step 4: Download the Quadrangle Archive File

In the quadrangle listing on the left side of the screen, each quadrangle will have an indicator if it is downloaded. The image below shows the 1:24,000 downloader with a list of quadrangles on its left side. If a quadrangle is downloadable, you can click on the download button. Your browser will open an FTP session to download the selected quadrangle's archive to your computer. It should allow you a chance to save the file to a directory of your choosing on your computer.

The image to the right shows a close-up of the image above. It shows the quadrangle listing after the map has been zoom into the eastern side of Washington Parish. Notice the "Baxterville SW" quadrangle is not downloadable since it has the symbol under it, yet the "Angie" and "Bogalusa East" quadrangles are with the symbol.

You can center the map on any one of the quadrangles by clicking on the button under the quadrangles.

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Step 5: Extract the Quadrangle Files from the Archive File

The Types of Files that are Downloaded

There are two different types of the files that are downloaded. One type is the .exe file type which is a self-extracting Zip archive file. This means that once you download the file, you need to double-left click on the file. It will automatically extract all the files bundled into the SAME DIRECTORY as the .exe file. The other type of archive file is the .zip file. It too is a Winzip archive, but you must use Winzip or some other software to extract the files. If you already have Winzip loaded onto your system, double-left click on the .zip file. Windows should.

A 30-day trial copy of Winzip can be downloaded from the Winzip site. Ordering information is available for fully registered copies of Winzip. To visit the Winzip site and download the trial copy of Winzip, click on the Winzip logo. Visit Winzip's website


The Types of Files that are Extracted

For the scanned USGS topographic maps, there are two files that are extracted. The first file is a TIF file with a .tif extension. This tif file is also a Geotiff since it carries the geotiff header. The second file is an ASCII file known as a world file. Some GIS such as Intergraph GeoMedia or ERDAS Imagine can read the tif files and correctly place them in relation to the earth's surface. Other GIS such as older versions of ESRI ArcView need the world file to help it correctly place the image on the earth's surface so that latitude-longitudes can be read. These programs treat the image as like map, that is, the image has a scale, it has directions, and locations from the image can be given in earth coordinates such as latitude-longitude pairs or projection coordinates.

Graphic image processing software such as Adobe PhotoShop can also read the tif file; however, these programs do not recognize the Geotiff header. They treat the tif file as a picture and not like a map.

For the DOQQs, there are three files that are extracted. The first file is a MrSid compressed image file with a .sid extensionon the filename. The second file is an ASCII file which is a MrSid world file with a .sdw extension on the filename. The third file contains meta data about the image. Some GIS such as Intergraph GeoMedia can read the MrSid image directly. Other GIS such as ESRI ArcView can read the image file with extensions or modules that can be added. See you GIS vendor for details. The extension for ArcView can be obtained from the ESRI site.

LizardTech, the maker of MrSid, has a viewer. To visit the Lizardtech site and download the Stand Alone Viewer, click on the Lizardtech logo. Visit LizardTech's website

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Jumping Between the Downloaders

The banner across the top of the downloaders allow you to switch between the different downloaders. When you switch from one downloader to another, the map range is carried over so that the map of the downloader to which you are switching is located in the same part of the state. For example, below is the banner from the 1:24,000 downloader. If you had zoomed into Washington Parish and then clicked on the 1:100,000 downloader in the banner, the 1:100,000 would appear with its map located on Washington Parish.

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Using the Right Mouse Button (for Windows users)

If you click the right mouse button anywhere inside the map itself, you will be presented with a "pop-up" menu of commands. The standard commands are as follows and are activated by clicking the command with the LEFT mouse button.  Standard commands include:

Fit - Click this command to see all of the graphics that have been downloaded in this particular session.
Zoom Box - Click this command , then drag a box over the area you wish to zoom in to. To drag a box, click and hold down the left mouse button at the top left corner of your desired area, move to the bottom left corner, and release the mouse button.
Zoom In - Click this command to zoom in around the center of the map - a 2X zoom factor
Zoom Out - Click this command to zoom out around the center of the map - a 2X zoom factor
Magnify - Click this command to create a magnifier window. Then as you move your cursor over the map, a magnified view at your cursor position will be displayed in the magnifier. In Netscape Navigator, click on the "Close" button to remove the magnifier. In Internet Explorer, a single click the right button anywhere will remove it.

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Accessing the Control/Plugin for Viewing the Webmaps

For instructions on loading the correct control or plugin for displaying webmaps, click here.

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